tag:blogger.com,1999:blog-8548646563861781742024-03-12T19:06:20.806-07:00...............EVOLUTIONARY PSYCHOLOGY.............EVOLUTIONARY PSYCHOLOGY is a forum for commentary, discussion, essays, news, and reviews that illuminate the theory of evolution and its implications for psychology in original and insightful ways. Unless otherwise noted, all materials may be quoted or re-published in full, with attribution to the author and EVOLUTIONARY PSYCHOLOGY. The views expressed herein do not necessarily reflect those of Cornell University, its administration, faculty, students, or staff.Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-854864656386178174.post-71393560519461865642013-01-31T21:19:00.000-08:002013-01-31T21:37:20.688-08:00<div class="separator" style="clear: both; text-align: center;">
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Ever since Darwin, evolutionary biologists have thought and written (and argued about) the evolution of cooperation. In the 20th century, at least three different major theories were proposed to explain how cooperation (and especially unselfish altruism) could evolve by natural selection. Several attempts to unify these theories have been made and are currently a topic of intense debate.<br />
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Now, as part of Cornell's Darwin Days celebration, you are invited to come to a dinner discussion to hear about, think about, talk about, and (hopefully) argue about these theories and their implications for human behavior, ethics, and philosophy.<br />
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PRESENTER: Allen MacNeill, Senior Lecturer in Biology and Evolution at Cornell and author of <i>Evolutionary Biology</i> and <i>Evolutionary Psychology</i><br />
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SPONSORS: Liebermania! and the Cornell Human Ethology Forum (this will also be the organizational meeting for CHEF)<br />
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DAY, TIME, & LOCATION: Thursday 14 February 2013 at 6:00 PM at Risley Dining/Tammany at Cornell University. This event is part of Cornell and PRI/MOTE's Darwin Day 2013 celebration.<br />
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Please contact Allen MacNeill at adm6@cornell.edu by Tuesday 12 February 2013 if you plan to attend this event. Hope to see you there!Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com1tag:blogger.com,1999:blog-854864656386178174.post-44440904132536439932011-03-17T06:21:00.000-07:002011-03-17T06:23:18.662-07:00Evolutionary Psychology: The Science of Human Nature<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrAY8HxIMA-c9tB9f3NIK4SZ3wbE_k8Llr-3-V8_z7NM-O0pcGz-SkUQ596dLYx2HtcjLxsvei26nTvBIVuBSCrZxyKoOgKHitQZ8geC0dx7EUcHCO04L3SqqUi1oLoFcLF7bhVM4TqbBd/s1600/MacNeill_A_%25282010%2529_Evolutionary_Psychology.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 216px; height: 216px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrAY8HxIMA-c9tB9f3NIK4SZ3wbE_k8Llr-3-V8_z7NM-O0pcGz-SkUQ596dLYx2HtcjLxsvei26nTvBIVuBSCrZxyKoOgKHitQZ8geC0dx7EUcHCO04L3SqqUi1oLoFcLF7bhVM4TqbBd/s320/MacNeill_A_%25282010%2529_Evolutionary_Psychology.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5585037675116997282" /></a><br />Having been tickled by Google Alert that my name had been mentioned in the comments at <a href="http://scienceblogs.com/pharyngula/2011/03/much_fuss_about_nothing_at_all.php" target="_blank"><i>Pharyngula</i></a> (P. Z. Myer's blog), I took a quick look. Just a few comments for now:<br /><br />1) I became an evolutionary psychologist when studying the behavioral ecology of <a href="http://en.wikipedia.org/wiki/Microtus_pennsylvanicus" target="_blank"><i>Microtus pennsylvanicus</i></a> got boring. Those cute little field voles got boring because their ethology is relatively simple. Human ethology is a lot more interesting, mostly because it is a lot more complex. Should we not try to study it because it is more complex? Or because it might not jibe with some people's political preconceptions?<br /><br />2) I assign <a href="http://ethomas.web.wesleyan.edu/wescourses/2004s/ees227/01/spandrels.html" target="_blank">Gould & Lewontin's "spandrels" paper</a> to my students in evolutionary biology, along with various criticisms of it. I also assign <a href="http://www.blackwellpublishing.com/ridley/classictexts/eldredge.pdf" target="_blank">Eldredge & Gould's "punk eek" paper</a> and <a href="http://en.wikipedia.org/wiki/Exaptation" target="_blank">Gould and Vrba's "exaptation" paper</a> (along with close to three dozen others, not to mention the entire <a href="http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=1" target="_blank"><i>Origin of Species, 1st. ed.</i></a>). I also give them chunks of George William's 1966 classic, <a href="http://en.wikipedia.org/wiki/Adaptation_and_Natural_Selection" target="_blank"><i>Adaptation and Natural Selection</i></a>, so that they will know exactly how "onerous" the concept of "adaptation" actually is.<br /> <br />3) Here's the definition of "adaptation" I use:<br /><blockquote>An <b><i>evolutionary adaptation</i></b> is any heritable phenotypic character whose frequency of appearance in a population is the result of increased reproductive success relative to alternative versions of that heritable phenotypic character.</blockquote>4) Here are the criteria I believe are most useful when one is attempting to determine if one is dealing with an "adaptation":<br /><blockquote><b>Qualification 1:</b> An evolutionary adaptation will be expressed by most of the members of a given population, in a pattern that approximates a normal distribution;<br /><br /><b>Qualification 2:</b> An evolutionary adaptation can be correlated with underlying anatomical and physiological structures, which constitute the efficient (or proximate) cause of the evolution of the adaptation;<br /><br /><b>Qualification 3:</b> An evolutionary adaptation can be correlated with a pre-existing evolutionary environment of adaptation (EEA), the circumstances of which can then be correlated with differential survival and reproduction; and <br /><br /><b>Qualification 4:</b> An evolutionary adaptation can be correlated with the presence and expression of an underlying gene or gene complex, which directly or indirectly causes and influences the expression of the phenotypic trait that constitutes the adaptation.</blockquote>To me, it seems reasonable that if one can apply those to a specific human behavior, one can make arguments about its evolutionary derivation. Would anyone disagree?<br /><br />As for the ridiculous idea that evolutionary psychology only deals with sex, has anyone making such a claim actually read a textbook on the subject? Here are several:<br /><br /><a href="http://www.amazon.com/Human-Evolutionary-Psychology-Louise-Barrett/dp/0691096228/ref=sr_1_1?ie=UTF8&s=books&qid=1300359675&sr=8-1" target="_blank"><i>Human Evolutionary Psychology</i></a><br /><br /><a href="http://www.amazon.com/Evolutionary-Psychology-New-Science-Mind/dp/020501562X/ref=sr_1_1?s=books&ie=UTF8&qid=1300359784&sr=1-1" target="_blank"><i>Evolutionary Psychology: The New Science of the Mind (4th Edition)</i></a><br /><br /><a href="http://www.amazon.com/Evolution-Human-Behavior-2nd-Perspectives/dp/0262533049/ref=sr_1_2?s=books&ie=UTF8&qid=1300359928&sr=1-2" target="_blank"><i>Evolution and Human Behavior, 2nd Edition: Darwinian Perspectives on Human Nature</i></a><br /><br /><a href="http://www.amazon.com/Modern-Scholar-Evolutionary-Psychology-Science/dp/B00435HBGO/ref=sr_1_1?ie=UTF8&s=books&qid=1300359983&sr=1-1" target="_blank"><i>Evolutionary Psychology: The Science of Human Nature</i></a><br /><br />[Full Disclosure Notice: The fourth title is indeed by <a href="http://www.blogger.com/profile/18378908" target="_blank"><i>Yours Truly</i></a>.]<br /><br />If you haven't, then please do so, and then we can discuss these questions.<br /><br />While we're on the subject, Part II of <a href="http://www.amazon.com/Modern-Scholar-Evolutionary-Psychology-Science/dp/B00435HBGO/ref=sr_1_1?ie=UTF8&s=books&qid=1300359983&sr=1-1" target="_blank"><i>Evolutionary Psychology: The Science of Human Nature</i></a> (on the ethology of between-group behavior in humans) is coming out in May. My next project is an introductory textbook in evolutionary biology, entitled <i>Evolutionary Biology: The Darwinian Revolutions</i>, again in two parts. Part I (due out in September) is <i>The Modern Synthesis</i> and Part II (due out next May) is <i>The Evolving Synthesis</i>.<br /><br />After that (if I live that long) will be <i>On Purpose: The Evolution of Design by Means of Natural Selection</i> (won't there be some fireworks when that comes out?), in which I present one of the core arguments for <i>The Metaphysical Foundations of the Biological Sciences</i>, in the spirit of <a href="http://en.wikipedia.org/wiki/Edwin_Arthur_Burtt" target="_blank">E. A. Burtt's <i>The Metaphysical Foundations of Modern Physical Science</i></a>. Should be fun!<br /><br />************************************************<br /><br />As always, comments, criticisms, and suggestions are warmly welcomed!<br /><br />--<a href="mailto:adm6@cornell.edu">Allen</a>Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com6tag:blogger.com,1999:blog-854864656386178174.post-84217833924535392062009-03-26T06:43:00.000-07:002009-03-27T14:27:02.929-07:00The Modern Evolutionary Synthesis<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxWzw5VECFUhyiWsjmwV5QtPBfBa1QuZ1DZL9V7UQb2_7kY-rxTN8qTsvt0WLfVXmC9fHxrY-Sl_zUdgyb6YOSha8n4-t5pmHhjeleZC5hc_i__O42Pkgkf5t0ZPZ7C-4hK3wGKJOl1VQ/s1600-h/Stebbins_Simpson_Dobzhansky.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 217px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxWzw5VECFUhyiWsjmwV5QtPBfBa1QuZ1DZL9V7UQb2_7kY-rxTN8qTsvt0WLfVXmC9fHxrY-Sl_zUdgyb6YOSha8n4-t5pmHhjeleZC5hc_i__O42Pkgkf5t0ZPZ7C-4hK3wGKJOl1VQ/s400/Stebbins_Simpson_Dobzhansky.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317982182630126754" /></a><br /><strong>SUMMARY</strong><br /><br />Darwin was largely successful in convincing scientists that evolution had occurred, but less successful in convincing them that the primary mechanism for evolution was natural selection. This was because natural selection absolutely requires continuous variation within populations, but the theory of “blended inheritance” that was common prior to 1900 strongly implied that such variations would eventually disappear. <br /><br />The rediscovery of Mendel’s theory of non-blending inheritance paradoxically made Darwin’s theory seem even less likely, as geneticists at the turn of the century believed that evolution occurred via mutation, rather than natural selection. However, the founders of theoretical population genetics eventually united Darwinian evolutionary theory and Mendelian genetics in what is now known as the “modern evolutionary synthesis.” In particular, the mathematical principles upon which the “modern synthesis” was based transformed evolutionary theory into a rigorous and testable natural science. Ever since the formulation of the “modern synthesis,” this is how evolutionary biology has proceeded: by an alternation between the formulation of theoretical mathematical models and rigorous, naturalistic field and laboratory studies.<br /><br /><strong>EVOLUTIONARY PSYCHOLOGY 1.1.6:</strong><br /><br />In the years following the publication of the <i>Origin of Species</i> in 1859, Darwin’s theory of evolution became widely accepted throughout most of the scientific community. Other naturalists, including such “leading lights” as Charles Lyell, Joseph Hooker, Asa Grey, and especially Thomas Henry Huxley quickly came to accept Darwin’s assertion that what he called “descent with modification” had in fact occurred. <br /><br />However, scientific opinion was much more divided on the subject of natural selection, Darwin’s proposed mechanism for evolution. To understand why, let’s quickly review the three preconditions Darwin proposed as the necessary prerequisites for natural selection. They are:<br /><br /><strong>• Variation between the members of populations:</strong> These variations need not be extreme, as illustrated by the relatively large changes that animal and plant breeders have accomplished, using relatively slight differences in physical appearance and behavior.<br /><br /><strong>• Inheritance:</strong> The distinct variations noted above must be heritable from parents to offspring.<br /><br /><strong>• Fecundity:</strong> Living organisms have a tendency to produce more offspring than can possibly survive. Among those individuals that do survive, those that also reproduce pass on to their offspring whatever characteristics made it possible for them to survive and reproduce.<br /><br />Given these prerequisites, then the natural outcome is:<br /><br /><strong>• Non-Random, Unequal Survival and Reproduction:</strong> Survival and reproduction are almost never random. Individuals survive and successfully reproduce because of their characteristics. It is these characteristics which form the basis for evolutionary adaptations.<br /><br />Considering these four ideas, we can ask the question, “What is the ultimate source of the new characteristics that are preserved and promulgated from generation to generation?” The answer is, “The ultimate source of all new characteristics is the ‘engines of variation’ – that is, those processes that produce the natural variation between individuals that Darwin emphasized as being absolutely necessary for the operation of natural selection". In a nutshell:<br /><blockquote><strong><i>Variation between individuals</i> is the key to evolution by natural selection.</strong></blockquote><br />However, in the <i>Origin</i>, Darwin summarized his presentation of his views on variation with this statement:<br /><blockquote><strong>"Our ignorance of the laws of variation is profound."</strong></blockquote><br />Neither Darwin nor any of his contemporaries (that he knew of) had a coherent theory of heredity or variation. However, this was not an insuperable obstacle to Darwin. Instead of giving up his argument, he simply accepted as a given that many important traits of animals and plants are heritable (pointing again to the observable facts of inheritance in domesticated animals and plants). He also proposed that, although he had no explanation of how they arose, variations among the members of a species do indeed occur, and can provide the raw material for natural selection.<br /><br />There were therefore two reasons why Darwin’s proposed mechanism of natural selection was not widely accepted, even among scientists:<br /><br />• Many of Darwin's contemporaries (and, in fact, Darwin himself) believed in Lamark's assertion that acquired characteristics could be inherited through use and disuse. This process directly contradicts the blind and purposeless process of natural selection, and therefore held the door open for purpose in evolution.<br /><br />• The consensus among naturalists was that inheritance worked by "blending" the characteristics of parents, which would cause any incipient adaptations to be diluted out of existence.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicidfFZ6iFgnFSxAbUTQG0OhvYtYWAW5M2JkXzoRnJ9rj9ixlgwSbivr6xC-gG7yjOXEfiOHLTv3MNai16wyr__n9-OME7Sg1Qey0_CM1tmvloelWOKGla3G-R9e7ImKgt8BR1iklolhM/s1600-h/Fleeming_Jenkin_BW.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 216px; height: 302px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicidfFZ6iFgnFSxAbUTQG0OhvYtYWAW5M2JkXzoRnJ9rj9ixlgwSbivr6xC-gG7yjOXEfiOHLTv3MNai16wyr__n9-OME7Sg1Qey0_CM1tmvloelWOKGla3G-R9e7ImKgt8BR1iklolhM/s320/Fleeming_Jenkin_BW.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317514821716051186" /></a><br />This second objection to Darwin's mechanism of natural selection was almost fatal to his theory. In an influential review of the <i>Origin</i>, written in 1867 by Fleeming Jenkin (a very well-respected English engineer and designer of the first trans-Atlantic telegraph cable), Jenkin pointed out that blending inheritance would eliminate variation within a few generations:<br /><blockquote>“However slow the rate of variation might be, even though it were only one part in a thousand per twenty or two thousand generations, yet if it were constant or erratic we might believe that, in untold time, it would lead to untold distance; but if in every case we find that deviation from an average individual can be rapidly effected at first, and that the rate of deviation steadily diminishes till it reaches an almost imperceptible amount, then we are as much entitled to assume a limit to the possible deviation as we are to the progress of a cannon-ball from a knowledge of the law of diminution in its speed.”</blockquote><br />If (as most naturalists of Darwin's time believed) all traits were blended from generation to generation, all of the distinctiveness of each variation would be lost and the population would remain essentially unchanged. Darwin got around this objection by proposing that large numbers of new variations (i.e. mutations) occur with each new generation. He called these “continuous variations,” but did not propose a mechanism for how they might be produced. <br /><br /><strong>Mendelian Genetics</strong><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimy-0k5NcZVF8cRNj5xASymGwpx1mLD-gDkzN1J0Sbjqw-vRKOu0TldvVqKw4ZIZhW_tSJ-THBx_PO56BP0SgDrVHPrMzCjYRTl2JPrq3OQqjuxW3HG_J7fhvqPdazFYJ_wnuzK_Yr09s/s1600-h/Gregor_Mendel_BW.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 214px; height: 319px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimy-0k5NcZVF8cRNj5xASymGwpx1mLD-gDkzN1J0Sbjqw-vRKOu0TldvVqKw4ZIZhW_tSJ-THBx_PO56BP0SgDrVHPrMzCjYRTl2JPrq3OQqjuxW3HG_J7fhvqPdazFYJ_wnuzK_Yr09s/s320/Gregor_Mendel_BW.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317515002932536898" /></a><br />However, at about the same time that Darwin was working out his ideas on natural selection and evolution, Gregor Mendel was working out a revolutionary new theory of genetics. Mendel was born in 1822 in Moravia, a province of the Austrian Empire (now part of the Czech Republic). Because he was a peasant's son, Mendel was expected to return to the family farm after finishing his education. However, Mendel was not satisfied with all that he had learned. The university, instead of answering his questions, instilled in him an insatiable curiosity about nature. <br /><br />Mendel observed that some offspring of some organisms had traits that were similar to only one parent, rather than being intermediate between both. He explained this phenomenon by assuming that heredity was determined by tiny, discrete “particles of inheritance” that were passed from the parents to the offspring via the reproductive cells. This would explain how some traits could remain unblended in the next generation. <br /><br />Such thinking stemmed from Mendel's physics training. In physics, all of nature is considered to be subject to laws based on the existence of and interactions between small, indestructible particles of matter. The goal of a physicist is to learn about the laws that determine the behavior of the particles. An investigator can sometimes work out these laws through careful experimentation. Mendel believed that these same methods could be used to study inheritance in living things.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJOd_e74eeHXpzt2htllCgC2ZQem5qBbNEMcXQ6hcijsQqqgqgrp8Em_K5mMK9bRt7OEBO8aehuhEJLsPc5e9rQJguJReHb0yA3q7_1s4TjwAjEoPYX3H-k_Rw4FV1pjTxoip7pq0xve8/s1600-h/Mendelian_Genetics_Pea_Traits.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 207px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJOd_e74eeHXpzt2htllCgC2ZQem5qBbNEMcXQ6hcijsQqqgqgrp8Em_K5mMK9bRt7OEBO8aehuhEJLsPc5e9rQJguJReHb0yA3q7_1s4TjwAjEoPYX3H-k_Rw4FV1pjTxoip7pq0xve8/s400/Mendelian_Genetics_Pea_Traits.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317515229529744594" /></a><br />In his paper, "Experiments in Plant Hybridization” (<i>"Versuche über Pflanzen-hybriden"</i>), published in 1866, Mendel tells how he used the garden pea plant to study the laws of heredity. His techniques differed from those of other investigators in three ways: <br /><br />(1) Mendel looked at one trait at a time; <br /><br />(2) He followed this trait from generation to generation over eight years; and <br /><br />(3) He used larger numbers of organisms in his studies. At the end of his experiments, he had carefully observed over 12,000 plants. <br /><br />In his most famous set of experiments, Mendel studied 22 varieties of plants of the same species: the common garden pea. He studied a total of seven different traits, each with two alternative forms, including seed shape, color, and seed coat color; pod shape and color, flower position on the stem, and stem height. For example, in one series of experiments, Mendel crossed pea plants that produced round seeds with pea plants that produced wrinkled seeds, and then observed what kinds of seeds were produced as the result of this cross over two generations.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmJYA9GEFtGGb_kjIe3o4-zvOUnb97x5ejDnvrTMzTEgU28Lkt6Dr2trPsxRvYnn7jyLpgs2UfeZw8JbcLinhtlsE6J6LbWTpghOQLUXQpI36WkJMbL_AqgQd3JU_vs8llmKqSaA-q7L4/s1600-h/RR_X_rr_Punnett_Square.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 308px; height: 253px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmJYA9GEFtGGb_kjIe3o4-zvOUnb97x5ejDnvrTMzTEgU28Lkt6Dr2trPsxRvYnn7jyLpgs2UfeZw8JbcLinhtlsE6J6LbWTpghOQLUXQpI36WkJMbL_AqgQd3JU_vs8llmKqSaA-q7L4/s400/RR_X_rr_Punnett_Square.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317528869610713586" /></a><br />Mendel observed that the two forms of each of these traits did not blend with each other. Among the offspring of the first cross, only one form of each trait showed up; the alternative form seemed to be lost. For example, when peas with round seeds were crossed with peas with wrinkled seeds, the first generation of offspring only produced round seeds.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgh8Y0tMeZhLDGUZh0ZNqlJ-3RCuyZTrYJjOh3DTLc7G8VwA9WqIPLca0I7VBVNI7bckQapmZ5Y5Pe4om-RVYi6gqbFP9OA8rcqnEMmqMp376inrSgqOctLXRAF5QF7T2uHdId0nBeQR84/s1600-h/Rr_X_Rr._Punnett_Square.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 308px; height: 253px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgh8Y0tMeZhLDGUZh0ZNqlJ-3RCuyZTrYJjOh3DTLc7G8VwA9WqIPLca0I7VBVNI7bckQapmZ5Y5Pe4om-RVYi6gqbFP9OA8rcqnEMmqMp376inrSgqOctLXRAF5QF7T2uHdId0nBeQR84/s400/Rr_X_Rr._Punnett_Square.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317529151788186770" /></a><br />However, in the second generation, the seemingly lost form showed up again. In our previous example, wrinkled seeds showed up again in the second generation of offspring, comprising approximately one-fourth of all of the offspring of that cross. Mendel explained this result by saying that the lost form of each trait was actually latent or cancelled by the expressed form. He called the prevailing form of a trait dominant and the latent form of a trait recessive. Mendel's definitions of dominance and recessiveness are sometimes called <strong>Mendel's Law of Dominance:</strong><br /><blockquote><strong><i>Dominant</i> traits mask the appearance of <i>recessive</i> traits whenever dominant and recessive traits are combined in one individual.</strong></blockquote><br />In our example, the gene for seed shape has two different forms. One form produces round seeds; the other form produces wrinkled seeds. Different gene forms that produce different forms of a trait are called alleles (from the Greek allos for "other"). In this example, the allele that codes for round seeds is dominant to the allele that codes for wrinkled seeds. <br /><br />Mendel observed that dominant and recessive forms of a trait did not become blended. Instead, the recessive form of the trait reappeared in an unaltered form in the second generation. Based on this observation, Mendel formulated his <strong>Law of Segregation</strong>, which states that:<br /><blockquote><strong>The different forms of a trait remain separate and <i>unblended</i> from generation to generation.</strong></blockquote><br />Mendel was so convinced of the validity of his conclusions that his subsequent work with other plants, some of which failed to support his hypothesis, did not discourage him. As he wrote in 1866, <br /><blockquote>"It requires indeed some courage to undertake a labour of such far-reaching extent; this appears, however, to be the only right way by which we can finally reach the solution of a question the importance of which cannot be overestimated in connection with the history of the evolution of organic forms."</blockquote><br />Late in his life, Mendel's time was mostly spent fighting political battles for the monastery and peasants of his village. In his lifetime, Mendel witnessed a complete change in his homeland. In his later years, the focus was no longer on agricultural advances but on political advances. The rise of the Hapsburg dynasty and the consolidation of the Austro-Hungarian Empire forced different values on the people. The days of intellectual freedom, when a monk could study agriculture in a monastery garden without interference by the government, were drawing to a close. Shortly before his death in 1884, Mendel said to a future abbot of the monastery:<br /><blockquote>"Though I have suffered some bitter moments in my life, I must thankfully admit that most of it has been pleasant and good. My scientific work has brought me a great deal of satisfaction, and I am convinced that it will not be long before the whole world acknowledges it."</blockquote> <br />Mendel's belief that his work would eventually be recognized was not mistaken. In 1900, only fourteen years after his death, his work was simultaneously rediscovered by three different geneticists – Carl Correns, Erich Tschermak, and Hugo de Vries – working in three different countries. They each realized that Mendel's particulate theory of inheritance fit patterns of inheritance they were observing. <br /><br />It is interesting to speculate what Darwin would have thought had he known about Mendel's work. Genes that did not blend in each generation were the answer to Darwin's dilemma, and could have put him onto the right track as early as 1866, the year Mendel's most important paper was published. A copy of the journal containing Mendel's paper was found in Darwin's library at Down House, but it had apparently not been opened or read.<br /><br /><strong>Evolution by Mutation</strong><br /><br />There is an even deeper irony: the rediscovery of Mendel's work led geneticists to reject natural selection as the mechanism for evolution, in favor of mutations. Hugo de Vries, one of the rediscoverers of Mendel's work, proposed that "mutations" (i.e. changes in the phenotype of an organism, occurring in just one generation) were the primary "engine" of evolutionary change. De Vries did his pioneering work in genetics using the evening primrose (<i>Oenothera lamarkiana</i>), which is now known for having sudden, large mutations (called "macromutations") in its overall phenotype.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigpZg1iwK8VO2rW_dj3bFwBUbBFL6U0fteNbIwzjXImQC6TOhNRPauHoqfjshjxGMalvZleVjhCp0hKv1tbimP0CuB5Qy_7J0spVnDx9iDWvc5cSOWBLF7JhRW582nsQDWeLFVvM5esuE/s1600-h/DeVries_Primrose.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 320px; height: 243px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigpZg1iwK8VO2rW_dj3bFwBUbBFL6U0fteNbIwzjXImQC6TOhNRPauHoqfjshjxGMalvZleVjhCp0hKv1tbimP0CuB5Qy_7J0spVnDx9iDWvc5cSOWBLF7JhRW582nsQDWeLFVvM5esuE/s320/DeVries_Primrose.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317515936882512226" /></a><br />De Vries argued that these kinds of mutations were the basis for the changes in phenotype to which Darwin referred in the <i>Origin of Species</i>, and that therefore natural selection was neither necessary nor likely as a cause of evolutionary change. This mutational theory of evolution was accepted by most of the prominent geneticists at the turn of the century, and led to widespread public testimonials that "Darwinism was dead."<br /><br />However, like Mark Twain, reports of Darwinism's death were "greatly exaggerated." In the second decade of the 20th century, three other researchers, again working separately and mostly unbeknownst to each other, proposed a theory that would eventually lead to the re-establishment of natural selection as the prime mover of evolution.<br /><br /><strong>The Hardy-Weinberg-Castle Genetic Equilibrium Law</strong><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5-MP45MpRKMqwyUUJ6Y20nSCAgYV3G3a3hyphenhyphen7tuMqr79hiyDEikttTeGZFTrVmmQuXYfB5AF_FSjWl7vYeaufmjBin-2rvpxgzxBfmiCdQ9bt0k3jue2EUUocLfZepU08tU-mP6oEZGco/s1600-h/Hardy_Weinberg_Castle.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 184px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5-MP45MpRKMqwyUUJ6Y20nSCAgYV3G3a3hyphenhyphen7tuMqr79hiyDEikttTeGZFTrVmmQuXYfB5AF_FSjWl7vYeaufmjBin-2rvpxgzxBfmiCdQ9bt0k3jue2EUUocLfZepU08tU-mP6oEZGco/s400/Hardy_Weinberg_Castle.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317980533541110226" /></a><br />G. C. Hardy, Wilhelm Weinberg, and William Castle all proposed a mathematical theory that describes in detail the conditions that must be met for evolution to not occur. This theory, often called the Hardy-Weinberg Equilibrium Law lays out the conditions that must be met for there to be no changes in the allele frequency in a population of interbreeding organisms over time.<br /><br />Recall Mendel's definition of alleles: different forms of the same gene that produce different variations of a trait. In the context of evolution, alleles are what code for the phenotypes that change over time in an evolving population. Therefore, changes in the alleles present in a population will produce changes in the phenotypes present in that population. This, in a nutshell, is <strong>the genetic definition of evolution:</strong> <br /><blockquote><strong>Evolution is the result of changes in allele frequency in a population over time.</strong></blockquote><br />What Hardy, Weinberg, and Castle all realized is that for allele frequencies to not change in a population, five conditions must be met:<br /><br />• <strong>There must be <i>no</i> mutations</strong> (i.e. alleles cannot change into other, different alleles).<br /><br />• <strong>There must be <i>no</i> gene flow</strong> (i.e. individuals cannot enter or leave the population).<br /><br />• <strong>The population must be <i>very</i> large</strong> (i.e. random accidents cannot significantly alter allele frequences).<br /><br />• <strong>Survival must be <i>random</i></strong> (i.e. there can be no natural selection).<br /><br />• <strong>Reproduction must also be <i>random</i></strong> (i.e. there can be no sexual selection).<br /><br />Notice that the Hardy-Weinberg Equilibrium Law seems to say only that there are conditions under which evolution can't happen. Aren't we interested in those conditions in which evolution can happen? Yes, but notice what the Hardy-Weinberg Equilibrium Law gives us: it outlines exactly what processes are essential to prevent evolution, and therefore by negation shows us how evolution can happen.<br /><br />That is, if any of the five conditions for maintaining a Hardy-Weinberg equilibrium are not met, then evolution must be occurring. And, of course, virtually none of these conditions is never permanently met in any known natural population of organisms:<br /><br />• Mutations occur at a slow but steady rate in all known populations.<br /><br />• Many organisms, especially animals, enter (immigration) and leave (emigration) populations.<br /><br />• Most populations are not large enough to be unaffected by random changes in allele frequencies.<br /><br />• Survival is virtually <i>never</i> random.<br /><br />• Reproduction in organisms that can choose their mates is also virtually <i>never</i> random.<br /><br />Therefore, according to the Hardy-Weinberg Equilibrium Law, evolution (defined as changes in allele frequencies over time) must be occurring in virtually every population of living organisms. In other words, <br /><blockquote><strong>Evolution is as ubiquitous and inescapable as gravity.</strong></blockquote><br />The Hardy-Weinberg Equilibrium Law provided more than just a "null hypothesis" for genetic evolution. It also provided a mathematical basis for a more comprehensive theory of evolution in which natural selection, Mendelian genetics, paleontology, and comparative anatomy were combined in what is now known as the modern evolutionary synthesis. During the 1930s and 40s, R. A. Fisher, J. B. S. Haldane, Sewall Wright, and Theodosius Dobzhansky developed mathematical models for fitness, selection, and other evolutionary processes. These models were then applied to demographic data derived from artificial and natural populations of organisms in a rigorous (and ongoing) test of the validity of the neo-darwinian model for genetic evolution. As a result of their work, Darwin's theories of natural and sexual selection were combined with Mendelian genetics, biometry and statistics, demography, paleontology, comparative anatomy, botany, and (more recently) molecular genetics and ethology to produce a "grand unified theory" of the origin and evolution of life on Earth.<br /><br /><strong>The Genetical Theory of Natural Selection</strong><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiIDruTiLD_TRInxwtl-q8MgSIfq3z8wZjrfF7ei7qxBNenUUHjF_OVVHYQ3oo_Tog5ofe2ascHnPbPSnhyphenhyphentUlwpW0kOICxiX-w5GcWJg3Fka7LwBSAD7Vevxk8-kTGCuqVBINMqSyYvgw/s1600-h/Ronald_Fisher.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 216px; height: 288px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiIDruTiLD_TRInxwtl-q8MgSIfq3z8wZjrfF7ei7qxBNenUUHjF_OVVHYQ3oo_Tog5ofe2ascHnPbPSnhyphenhyphentUlwpW0kOICxiX-w5GcWJg3Fka7LwBSAD7Vevxk8-kTGCuqVBINMqSyYvgw/s320/Ronald_Fisher.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317516369054224898" /></a><br />Ronald Aylmer Fisher built on the pioneering theoretical work of Hardy, Weinberg, and Castle by providing mathematical models that further undermined the Mendelian geneticist's theory of evolution via mutation. He did this by showing that continuous variation could provide the basis for natural selection as proposed by Darwin. In his most important work, <i>The Genetical Theory of Natural Selection</i> (published in 1930) Fisher showed that traits characterized by continuous variation (i.e. those that approximate a normal, or bell-shaped, distribution) were both common and could provide all the raw material necessary for Darwinian natural selection. This is because such traits, although being continuous in populations, do not blend from parents to offspring. Instead, as Mendel first showed, they are produced by unblending "particles" of inheritance (i.e. Mendelian "genes"). In other words, <br /><blockquote><strong>Mendelian inheritance conserves, rather than eventually destroying, the genetic variation that exists in natural populations.</strong></blockquote><br />Fisher is perhaps best known for what he called the <strong>Fundamental Theorem of Natural Selection</strong>. Using a series of essentially mathematical arguments, Fisher showed that the rate of change via natural selection was a direct function of the amount of variation in a population. That is, <br /><blockquote>The more variation among alleles that exists in a population, the faster natural selection can causes changes in the allele frequencies in that population.</blockquote> <br />Conversely, the less variation among alleles that exists in a population, the slower natural selection can causes changes in the allele frequencies in that population.<br /><br />R. A. Fisher's work formed the basis for a mathematical theory of evolution in which the process of natural selection is modeled mathematically in the same way that Newton modeled the force of gravity. Indeed, Fisher pointed out several times that the mathematics of natural selection were similar in many ways to such physical models as the ideal gas laws and the second law of thermodynamics. According to his mathematical models, alleles that were positively selected would increase in frequency in populations in much the same was as gas molecules spread out in an expanding balloon.<br /><br />To many evolutionary biologists, this meant that natural selection would inevitably result in "fixation" of alleles that were not selected against. That is, <br /><blockquote><strong>Any allele that results in increased survival and reproduction should, if given enough time, eventually become the <i>only</i> allele for that particular trait in a particular population.</strong></blockquote><br />This presented a problem to evolutionary biologists that was almost as severe as the “mutationism” of the early Mendelians. It implied that the inevitable result of natural selection would be the eventual elimination of all non-adaptive variation in natural populations. This would then cause natural selection to grind to a halt (or to become reduced to essentially the rate of production of new genetic mutations, which is slow in the extreme, much slower than the observed rate of evolution). Fisher suggested that constant environmental change would cause different alleles to be selected for and against, and that therefore fixation might not ever happen. However, this argument seemed to be "tacked on" to his argument for the relationship between the amount of variation in populations and the speed of evolutionary change via natural selection. <br /><br /><strong>Adaptive Landscapes and Genetic Drift</strong> <br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZ0OGbZ9Dj0N0T6UdBKPcBQW_D6VGBDxuYOvN4awJvOj6xRL2jZhZCSWUd2cA0euAK-2U11l7SRVd3Lu5F_dfWYnh71bu9x0KZy5XK5mqcWRR-2LxMu_g7VG_hP1V_anwclgqiU3t0w0A/s1600-h/Sewall_Wright_BW.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 212px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZ0OGbZ9Dj0N0T6UdBKPcBQW_D6VGBDxuYOvN4awJvOj6xRL2jZhZCSWUd2cA0euAK-2U11l7SRVd3Lu5F_dfWYnh71bu9x0KZy5XK5mqcWRR-2LxMu_g7VG_hP1V_anwclgqiU3t0w0A/s320/Sewall_Wright_BW.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317516592176490162" /></a><br />A solution to this problem was provided by Sewall Wright, who discovered a process that has eventually become known as <i>genetic drift</i>. Wright, who worked primarily with domesticated animals in controlled breeding programs, proposed that in small populations of organisms, random sampling errors could cause significant changes in allele frequencies in those populations. He showed mathematically that the smaller a population was, the greater the effect of such random events on its allele frequencies. In other words, <br /><blockquote><strong>Evolution can proceed by at least <i>three</i> primary mechanisms: natural selection, sexual selection, and random genetic drift.</strong></blockquote><br />Wright's discovery of genetic drift solved the problem that Fisher's Fundamental Theorem posed: how can natural selection be prevented from shutting itself down as the result of fixation? Wright proposed that allele frequencies could be visualized as forming what he came to call an "adaptive landscape". In an adaptive landscape, allele frequencies formed a series of hills and valleys, in which the top of a hill represented the highest an allele frequency could reach via natural selection. According to Fisher, there is an iron-clad rule operating here: if an allele is on a slope, it can only go up the slope via natural selection.<br /> <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgo0ru-iRRDKAn-G6jx1KkzDPHSGBFg4gHC8N6TJcqbXB4EhjszLh427xFzRilZTJwn-5uZuSYBGvY3z_0gI6qbXXRQLYaW_vd5enLwkKEtnfMJwpVjIhJiynBZH7HbYc-9_nsJ5FEmwM4/s1600-h/Adaptive_Landscape_Moths.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 360px; height: 290px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgo0ru-iRRDKAn-G6jx1KkzDPHSGBFg4gHC8N6TJcqbXB4EhjszLh427xFzRilZTJwn-5uZuSYBGvY3z_0gI6qbXXRQLYaW_vd5enLwkKEtnfMJwpVjIhJiynBZH7HbYc-9_nsJ5FEmwM4/s400/Adaptive_Landscape_Moths.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317516849326904706" /></a><br />But this means "you can't get there from here": if a trait is at the top of one adaptive peak, it can't go down through a valley to get to the top of another, even higher (i.e. more adaptive) peak. What Wright showed was that "you <i>can</i> get there from here" if you <i>drift</i> there. That is, if a population becomes very small, it is possible for it to "drift" from one adaptive peak to another, without sliding down into the valley in between. This means that natural selection doesn't get "stuck"; populations at one adaptive peak can make it to another, even higher adaptive peak, so long as they drift randomly to it.<br /><br /><strong>The Causes of Evolution</strong><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgm4SapcLYUU-7jxI4wSpgo20LNYB4n7sahuiebiEX2BHEuOxo5UC5KVYYJFcfp-PKo4q3DpzD-1kUK7wr2w54vg2lYQcXtsi_scpXKFkLz33sp14XZeiIO-qn5E7FL4kV7ogVtgIwSS9I/s1600-h/J.B.S._Haldane.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 216px; height: 246px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgm4SapcLYUU-7jxI4wSpgo20LNYB4n7sahuiebiEX2BHEuOxo5UC5KVYYJFcfp-PKo4q3DpzD-1kUK7wr2w54vg2lYQcXtsi_scpXKFkLz33sp14XZeiIO-qn5E7FL4kV7ogVtgIwSS9I/s320/J.B.S._Haldane.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317517080034471218" /></a><br />John Burdon Sanderson Haldane (usually referred to as J. B. S. Haldane) solidified the revolution in theoretical population genetics begun by Hardy, Weinberg, Castle, Fisher, and Wright. In his most important book, <i>The Causes of Evolution</i>, published in 1932, he showed that genetic mutations could provide the raw material for Darwinian natural selection. Furthermore, he showed mathematically that such mutations could do this even when their frequency in a population was initially so low that they would be "invisible" to statistical analysis. He also showed how dominance could evolve in populations by means of natural selection, even when the original expression of an allele was initially recessive. <br /><br />Haldane is also remembered for two quips that are often repeated by evolutionary biologists. The first concerns a question posed to him by an Anglican minister, who asked him (supposedly at a dinner party) what his study of nature had led him to conclude about the principle concern of the Creator. Without batting an eyelash, Haldane replied: "An inordinate fondness for beetles," referring to the fact that there are more species of beetles on Earth than any other kind of organism. <br /><br />During another conversation (supposedly in a pub), Haldane was confronted with the observation that natural selection should result in pure selfishness on the part of individuals, and therefore no one should be willing to risk his own life to save another. To this Haldane replied, <br /><blockquote>"I would be willing to risk my life to save two brothers or eight cousins."</blockquote> <br />This quip is based upon the observation that brothers share an average of one-half of their genetic material, whereas first cousins share an average of one-eighth. Therefore, saving two brothers or four cousins would result in the same genetic contribution to the next generation as that represented by one's own genome. This quip was later cited by one of the founders of what is now know as the theory of kin selection in which natural selection is considered to act at the level of genes, rather than individuals. We will discuss this idea in a later chapter.<br /><br />R. A. Fisher, J. B. S. Haldane, and Sewall Wright are usually recognized as having laid the theoretical foundation for modern evolutionary theory. However, many evolutionary biologists and historians of science consider that the "modern evolutionary synthesis” was initiated by Theodosius Dobzhansky with the publication of his most famous book, <i>Genetics and the Origin of Species</i> published in 1937. <br /><br /><strong>Genetics and the Origin of Species</strong><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgw7gde38UzOK2DPBMyKP5yd3x07Xo4-iBH355MyirD34AXY8VIbzJDzYeBVLXesKhxr_y2ZiotvEMbsgXYnYEAwdvbop2NFHjXpOdePkXGWV96RrvuTtlq-DxZvApVa60N50KGKLM5Sqw/s1600-h/Theodosius_Dobzhansky_BW.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 208px; height: 320px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgw7gde38UzOK2DPBMyKP5yd3x07Xo4-iBH355MyirD34AXY8VIbzJDzYeBVLXesKhxr_y2ZiotvEMbsgXYnYEAwdvbop2NFHjXpOdePkXGWV96RrvuTtlq-DxZvApVa60N50KGKLM5Sqw/s320/Theodosius_Dobzhansky_BW.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317518938745496786" /></a><br />Dobzhansky combined the Mendelian genetics, the mathematical models of Fisher, Haldane, and Wright, and the observations of evolution and natural selection in the wild in a theory that reinstated natural selection as the primary engine of evolution. He emphasized both the scientific aspects of evolutionary theory, and the implications of evolutionary theory for education and society in general. In a famous essay entitled "Nothing in biology makes sense except in the light of evolution” he showed how modern synthetic evolutionary theory provides a comprehensive explanation for the origin and evolution of life on Earth. <br /><br />Dobzhansky also grounded the "modern evolutionary synthesis" in empirical investigation. Using the common fruit fly (<i>Drosophila melanogaster</i>). Dobzhansky and his colleagues showed that the patterns of variation and natural selection predicted by Fisher actually occurred in controlled populations of living organisms under laboratory conditions. <br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmZJjaV0AtxL4Z2_FcctZwwXHygrmnvUguSorqBJZjUmrkNw9ybd-Uv6Bl6vWRduyCVkwMG_pm4apho5dSesHz5Ph5n7IOJIpY2a9WGTZZIZh-vIqtdbvcO4nOa5MGPAsaEoyiWey45m0/s1600-h/Selection_Continuous_Variation.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 288px; height: 288px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmZJjaV0AtxL4Z2_FcctZwwXHygrmnvUguSorqBJZjUmrkNw9ybd-Uv6Bl6vWRduyCVkwMG_pm4apho5dSesHz5Ph5n7IOJIpY2a9WGTZZIZh-vIqtdbvcO4nOa5MGPAsaEoyiWey45m0/s400/Selection_Continuous_Variation.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317519124450499042" /></a><br />Most importantly, Dobzhansky showed empirically that the "continuous variation" that both Darwin and Fisher asserted were essential for natural selection actually occurred for many traits in nature. According to Dobzhansky, most traits are distributed in what is often referred to as a "bell-shaped curve". That is, for most traits there is an average value for the trait, which the majority of the members of the population share. There is also two "tails" to the bell-shaped curve, consisting of extreme versions of the trait. <br /><br />Dobzhansky then went on to identify three different forms of natural selection, which depended upon which part of the bell-shaped curve of variation selection affected:<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMCHnpG44Q-e82Zys_x0atq4U-H0lPNV6MgAUjVSxu6k58hYufaTSfPFqbbpVU9iVAmpndfg09V1RjE-THkxHf2LxN2fYQb5qRBuv5jqp3n2AOr4ucaVdEGi3Iu1cYOHew4G8ioJsUoHk/s1600-h/Selection_Directional.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 288px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMCHnpG44Q-e82Zys_x0atq4U-H0lPNV6MgAUjVSxu6k58hYufaTSfPFqbbpVU9iVAmpndfg09V1RjE-THkxHf2LxN2fYQb5qRBuv5jqp3n2AOr4ucaVdEGi3Iu1cYOHew4G8ioJsUoHk/s400/Selection_Directional.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317519378690711698" /></a><br /><strong>• Directional selection,</strong> in which selection against one extreme "tail" of the bell-shaped curve caused the average value for the trait to move over time;<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3E3c18EEPwc7GUj5wtN3Gw76iTJAmI0-iePoF0qRNcMHpwB-62hrmz7jxHChi6tFIJKKz5WPQMVfeYvRybJtO7CQ4fF-2FqACv0jRUTDN2Z0JTEusy8W2r6h5e4Sh8LAzddfoPNboA4U/s1600-h/Selection_Stabilizing.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 288px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3E3c18EEPwc7GUj5wtN3Gw76iTJAmI0-iePoF0qRNcMHpwB-62hrmz7jxHChi6tFIJKKz5WPQMVfeYvRybJtO7CQ4fF-2FqACv0jRUTDN2Z0JTEusy8W2r6h5e4Sh8LAzddfoPNboA4U/s400/Selection_Stabilizing.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317519891352978530" /></a><br /><strong>• Stabilizing selection,</strong> in which selection against both extreme "tails" of the bell-shaped curve caused the average value for the trait to remain where it was; and<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiO-Wy9A6-PgoBDCacclrVXnukSSiGC5qilUxw_tS2ljgQRMOKwuFUPwhfL9TV3Ce5xBc4ImzFGhQMTqaWTphg8xPJHJxh9WIH702cYxFys0jo274zvw1fO57EKS93Z280LrB3G4tltpLE/s1600-h/Selection_Disruptive.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 192px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiO-Wy9A6-PgoBDCacclrVXnukSSiGC5qilUxw_tS2ljgQRMOKwuFUPwhfL9TV3Ce5xBc4ImzFGhQMTqaWTphg8xPJHJxh9WIH702cYxFys0jo274zvw1fO57EKS93Z280LrB3G4tltpLE/s400/Selection_Disruptive.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5317520053004650082" /></a><br /><strong>• Disruptive selection,</strong> in which selection against the average value of the bell-shaped curve caused the population to split into two diverging curves, corresponding to the two extreme versions of the trait.<br /><br />The proponents of the "modern evolutionary synthesis" asserted that this last form of natural selection was the underlying explanation for the divergence of one species into two or more different species (for this reason, disruptive selection is sometimes referred to as "diversifying selection"). That is, Darwin's "mystery of mysteries" – the origin of species – was shown to have a mathematical basis which could be studied empirically and tested statistically, thereby making it a genuinely "scientific" study.<br /><br /><strong>The Historical Importance of the "Modern Evolutionary Synthesis"</strong><br /><br />What, then, was the importance of the “modern evolutionary synthesis” to evolutionary theory? Perhaps J.B.S. Haldane said it best:<br /><blockquote>"The permeation of biology by mathematics is only beginning, but unless the history of science is an inadequate guide, it will continue, and the investigations here summarized represent the beginning of a new branch of applied mathematics."</blockquote><br />The theory of evolution as Darwin first proposed it was essentially a qualitative theory; it had no mathematical basis, and could not be tested using statistical methods. Indeed, Darwin himself was a “mathophobe,” who had neither the training nor the inclination to provide a mathematical basis for his theories.<br /><br />However, the founders of the modern synthesis were all well-versed in mathematics, as was Gregor Mendel. Indeed, R. A. Fisher not only provided the first solid mathematical framework for the theory of evolution by natural selection, he virtually founded the disciplines of biometry and statistics. Many of the statistical tests that are still used to test evolutionary hypotheses (indeed, hypotheses throughout the natural and social sciences) were first formulated by Fisher.<br /><br />Providing a mathematical foundation for evolutionary theory literally meant converting evolution from “natural history” into a modern science. When a hypothesis can be tested by gathering numerical data (by counting or measuring objects and events), that data can then be statistically tested to determine if it verifies or falsifies that hypothesis. This is what happens in the other natural sciences, like chemistry and physics. Since the modern evolutionary synthesis, this is also what happens in evolutionary biology, and evolutionary psychology as well.<br /><br /><strong>Where Have We Been, and Where Are We Going?</strong><br /><br />With this chapter, we have come to the end of the first part of our series of chapters on evolutionary psychology. Now that we have a grounding in the theory of evolution by natural selection, it is time to take a quick look at the theories of psychology dealing with human and animal behavior. That will be our task in the next series of six chapters: “Psychology, Ethology, and Sociobiology.” In the course of those chapters, we will see how the seeds planted by Darwin, Mendel, and the founders of the modern synthesis took root in the 20th century, eventually coming to fruition in the modern science of evolutionary psychology.<br /><br />ESSENTIAL READING:<br /><br />Mayr, Ernst & William Provine (eds.) (1998) <i>The Evolutionary Synthesis: Perspectives on the Unification of Biology.</i> Harvard University Press. <br /><br />SUPPLEMENTAL READING:<br /><br />Darwin, Charles (1868) <i>The Variation of Animals and Plants Under Domestication.</i> John Murray. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=F877.1&viewtype=side&pageseq=1" target="_blank">here</a>.<br /><br />Dobzhansky, Theodosius (1937) <i>Genetics and the Origin of Species.</i> Columbia University Press.<br /><br />Dobzhansky, Theodosius (1973) Nothing in biology makes sense except in the light of evolution. <i>The American Biology Teacher</i>, March 1973, volume 35, pages 125-129. Available online <a href="http://people.delphiforums.com/lordorman/light.htm" target="_blank">here</a>.<br /><br />Fisher, R. A. (1930) <i>The Genetical Theory of Natural Selection.</i> Oxford University Press.<br /><br />Haldane, J. B. S. (1932) <i>The Causes of Evolution.</i> Princeton University Press.<br /><br />Jenkin, Fleeming (1867). [Review of] <i>The Origin of Species</i>. <i>The North British Review,</i> June 1867, 46, pp. 277-318. Available online <a href="http://www.scholars.nus.edu.sg/landow/victorian/science/science_texts/jenkins.html" target="_blank">here</a>.<br /><br />Mendel, Gregor (1866) Experiments in Plant Hybridization. <I>Verhandlungen des naturforschenden Vereines in Brünn</I>, volume 4, pages 3-47. Available (in English) online <a href="http://www.esp.org/graphics/page3.htm" target="_blank">here</a>.<br /><br />Provine, W. (1971) <i>The Origins of Theoretical Population Genetics.</i> University of Chicago Press. <br /><br />QUESTIONS TO CONSIDER:<br /><br />1. Why are mathematical models so important to the natural sciences? Are they necessary for something to be considered “scientific?”<br /><br />2. Is the evolutionary synthesis the “final word” on the subject of evolution? Why or why not?<br /><br />************************************************<br /><br />As always, comments, criticisms, and suggestions are warmly welcomed!<br /><br />--<a href="mailto:adm6@cornell.edu">Allen</a>Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com1tag:blogger.com,1999:blog-854864656386178174.post-50716882727356307672009-03-25T14:23:00.000-07:002009-03-25T14:24:01.110-07:00A Brief Note About Comment ModerationDue to the behavior of certain unnamed and unscrupulous individuals, I have found it necessary to return to full-time comment moderation at EVOLUTIONARY PSYCHOLOGY. This means that comments will not appear here until they have been emailed to me and I have approved them for posting to the comment threads following each post. Please bear this in mind when you comment here. Thank you for your patience and understanding.<br />--Allen MacNeill<br /><br />"I had at last got a theory by which to work"<br />-The Autobiography of Charles DarwinAllen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com1tag:blogger.com,1999:blog-854864656386178174.post-72053568256518455192009-03-22T19:04:00.000-07:002009-03-22T20:20:09.506-07:00Darwin on Instincts and the Expression of Emotions<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmGKLfb1eyzYLTQ-Lhe-kd9b6-ElxY9MTLZSmAxyXXDfEmdfx7BdoLWDiSnasNdqr8GpCqjbCdM6ioqFVoZlXc2IVFBB2GLh6YNzVYCYpHDBRHJm_N9-zTh6O95lTtlDWsoL5diQ6Of6Q/s1600-h/Profile_Face.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 216px; height: 294px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmGKLfb1eyzYLTQ-Lhe-kd9b6-ElxY9MTLZSmAxyXXDfEmdfx7BdoLWDiSnasNdqr8GpCqjbCdM6ioqFVoZlXc2IVFBB2GLh6YNzVYCYpHDBRHJm_N9-zTh6O95lTtlDWsoL5diQ6Of6Q/s320/Profile_Face.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5316198574712105794" /></a><br />SUMMARY<br /><br />In <a href=" http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=225" target="_blank"> Chapter VII of the <i>Origin of Species</i></a>, Darwin proposed that <a href="http://en.wikipedia.org/wiki/Instincts" target="_blank">instincts</a> were behavioral <a href="http://en.wikipedia.org/wiki/Adaptation" target="_blank">adaptations</a> that had evolved by <a href="http://en.wikipedia.org/wiki/Natural_selection" target="_blank">natural selection</a> and <a href="http://en.wikipedia.org/wiki/Sexual_selection" target="_blank">sexual selection</a>. Darwin provided many examples of instinctive behaviors in animals, and suggested how such behaviors could have evolved. In particular, he proposed that animal social behavior was the result of natural selection acting at the level of “families”, rather than individuals. <br /><br />In his later book, <a href=" http://darwin-online.org.uk/content/frameset?itemID=F1142&viewtype=side&pageseq=1" target="_blank"><i>On the Expression of Emotions in Men and Animals</i></a>, Darwin elaborated on the idea that behaviors are evolutionary adaptations that have evolved by natural and sexual selection. He explained the roles that emotions play in the biology of animals, and extended those explanations to humans. He argued that emotions are essentially biological processes analogous to other physiological adaptations, and that the methods by which they can be studied are similar to those by which any other inherited trait can be scientifically analyzed.<br /><br /><strong>EVOLUTIONARY PSYCHOLOGY 1.1.5</strong><br /><br />Near the end of the previous chapter, I mentioned that Darwin proposed in the <i>Origin of Species</i>, that “instincts” were behavioral adaptations that had evolved by natural and sexual selection. <br /><br /><a href="http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=225" target="_blank">In a chapter in the Origin entitled “Instincts,”</a> Darwin explored this idea in the light of his overall <a href="http://en.wikipedia.org/wiki/Evolution" target="_blank">theory of evolution by natural selection</a>. In particular, like many of his contemporaries Darwin was fascinated by the behavior of social insects, especially ants and bees. He pointed out that their highly specialized behavior and mode of reproduction posed a serious problem for his theory, a problem that he needed very much to solve.<br /><br /><strong>Darwin on Instincts</strong><br /><br />In the chapter on instincts, Darwin was very careful to distinguish between the evolution of intelligence and the evolution of instincts. In the <i>Origin</i>, Darwin did not speculate about the evolution of intelligence at all, but rather confined his discussion to the behavior of non-human animals. However, he did make it clear that he believed that there were strong analogies between some of the instinctive behaviors of non-human animals and similar behaviors in humans.<br /><br />Darwin initially avoided defining “instincts” directly. Instead, he provided multiple examples of the kinds of behaviors he was referring to when he used the term “instinct.” In other words, he used the kind of <span style="font-weight: bold; color: rgb(51, 51, 255);"><i>functional analysis</i></span> that I described in the <a href="http://evolpsychology.blogspot.com/2009/02/natural-selection-and-evolutionary.html" target="_blank">previous chapter</a>. We will see this technique being used over and over again, not only in evolutionary biology as a whole, but especially in evolutionary psychology.<br /><br />The examples of instincts cited by Darwin in the Origin have the following properties:<br /><br />1. Instincts are <i>not</i> acquired (i.e. learned) via experience.<br /><br />2. On the contrary, instincts can be performed by individuals who have never learned how to perform them, nor experienced the same set of stimuli before in their lives. <br /><br />3. In particular, instinctive behaviors can be elicited from animals that have been raised in isolation since birth (or since hatching, as often the animals being tested were birds).<br /><br />4. Instincts are <span style="font-weight: bold; color: rgb(51, 51, 255);"><i>stereotyped</i></span>. That is, they are performed in very much the same way every time, both by the same individual at different times and by most of the members of a given species (i.e. they can be referred to as <span style="font-weight: bold; color: rgb(51, 51, 255);"><i>pan-specific</i></span> behaviors).<br /><br />5. Furthermore (and in contrast with many human behaviors), instinctive behaviors do <i>not</i> seem to require judgment or reason on the part of the individuals performing them.<br /><br />6. By implication, this means that instincts are essentially unconscious; that is, they are <i>not</i> the result of conscious deliberation or intentions. <br /><br />Darwin also took great pains to distinguish between “instincts” and “habits.” He pointed out that <span style="font-weight: bold; color: rgb(51, 51, 255);"><i>habits</i></span> are stereotyped behaviors that are acquired during an individual’s lifetime, usually by constant repetition. However, Darwin also believed that some habits could be inherited, especially as the result of use and disuse. In that respect, Darwin clearly believed in the possibility that evolution could proceed by the inheritance of acquired characteristics, a theory proposed a half century earlier by the Frenchman, <a href="http://en.wikipedia.org/wiki/Lamarck" target="_blank">Jean-Baptiste Lamarck</a>. If he were referring to anatomical or physiological characteristics, we would be safe in rejecting Darwin’s assertion that acquired traits such as habits can be inherited. As <a href="http://en.wikipedia.org/wiki/August_Weismann" target="_blank">August Weismann</a> and others showed, acquired anatomical characteristics (such as missing tails in mice, chopped off by the experimenter) <i>cannot</i> be inherited from parents to offspring.<br /><br />However, some behaviors are learned from other individuals, and not just from parents to offspring. To the extent that a behavior can be learned or modified during an individual’s lifetime that behavior is essentially <i>an acquired trait that <strong>can</strong> be passed on</i> (i.e. “inherited”). Some behaviors, in other words, follow the rules of Lamarckian evolution. As we will see, there is evidence that we inherit (via Darwinian mechanisms) the tendency to learn certain behaviors (via Lamarckian mechanisms), and that we learn such behaviors surprisingly easily.<br /><br />In the <i>Origin</i>, Darwin focused most of his attention on the instincts of “lower” animals, especially the social insects. One of the reasons for this was that such behaviors could be explained without including either consciousness or intelligence. Furthermore, Darwin took pains to show that instincts have many of the characteristics of evolutionary adaptations:<br /><br />1. Although they are pan-specific, most instincts are quite variable, both within and between individuals.<br /><br />2. Like other adaptations, the instincts that are present in a population (or species) apparently change slowly and gradually over time.<br /><br />3. Instincts provide a benefit primarily to the individuals performing them, and especially not to the members of other species.<br /><br />4. Instincts, like other adaptations, are <i>not</i> perfect. Rather, they are compromises that only have to function “well enough” to result in differential survival and reproduction.<br /><br />5. Finally, and most importantly: <br /><blockquote><strong>The performance of specific instincts can be causally linked to increased survival and reproduction by the individuals performing them.</strong></blockquote><br />Darwin also took great pains to show that many instincts are inherited virtually unchanged from parents to offspring. The best way to do this is to show that an instinctive behavior is performed correctly without any opportunity for the performer to have learned it through experience. Darwin noted that <a href="<br />http://en.wikipedia.org/wiki/Pointer_(dog)" target="_blank">pointers</a> (dogs used to assist in hunting game birds) do not need to be trained in how to “point” at their quarry. On the contrary, they need to be trained to hold still when a gun is fired, and not to maul a bird if it is shot and lands nearby. “Pointing”, in other words, is an instinctive behavior that has been bred into some hunting dogs.<br /><br />The heart of Darwin’s chapter on instincts in the <i>Origin</i> is his explanation for the evolution of <a href="http://en.wikipedia.org/wiki/Eusociality" target="_blank">sterile castes</a> in the social ants, bees, termites, and wasps. He started out by pointing out that if he cannot do this, it would be “fatal” to his entire theory. The reason for this is that he had previously and repeatedly asserted that traits that provide a benefit exclusively to another organism <i>cannot</i> possibly evolve by natural selection. This is because the other individuals (the ones receiving the benefit) would therefore increase in frequency in the population, while the individuals providing the benefit would decrease in frequency until they disappeared, leaving only those individuals who did not provide the benefit.<br /><br />Darwin correctly pointed out that this problem would be most acute for the social insects, because many of them have what are known as sterile castes, such as workers, warriors, etc. These are often highly modified versions of the average ant, bee, termite, or wasp, with gigantic jaws, reduced or absent wings, etc. Furthermore (and most importantly) such specialized castes consist of individuals that are sterile: they never reproduce during their own lifetimes, but rather assist the <a href="http://en.wikipedia.org/wiki/Gyne" target="_blank">“queen”</a> ant, bee, termite, or wasp in reproducing.<br /><br />Here, then is Darwin’s potentially fatal quandary: how can an adaptation like gigantic jaws be passed on at rates sufficient to make them more common over time if the individuals that have such traits never reproduce? Stated succinctly: <br /><blockquote><strong>How can a sterile worker pass on the trait of sterility?</strong></blockquote><br />Darwin’s answer was surprisingly simple: he proposed that natural selection could act at the level of “families” (i.e. groups), rather than exclusively at the level of individuals. Darwin pointed out that the problem of the evolution of sterile castes in social insects is essentially the same as the problem of how to continue getting high quality meat from domesticated farm animals, such as beef cattle. After all, when a steer is slaughtered and cut up for meat, it can’t very well pass on the traits (thick muscles, marbled fat, etc.) that made it a superior source of beef. For that matter, a steer is already out of the evolutionary race even before it is slaughtered. “Steers” are male cattle that have been castrated (which makes them fatter and more placid). Like the members of a sterile caste of social insects, steers are sterile, and therefore cannot possibly pass on to their offspring the characteristics that make them so valuable as a source of food.<br /><br />So, Darwin asked, how do we continue to obtain high-quality meat from animals that are castrated and then slaughtered, rather than being bred? The answer is, we breed their closest relatives, who presumably carry the same genetic traits that made their slaughtered relatives so valuable. In other words, <i>we select for a closely related group of individuals</i>, who can therefore evolve particular desirable traits, without all of them necessarily surviving and reproducing.<br /><br />In the same way, the reproductive members of a hive of social insects (i.e. the <a href="http://en.wikipedia.org/wiki/Gyne" target="_blank">“queens”</a> and <a href="http://en.wikipedia.org/wiki/Drone_(bee)" target="_blank">“drones”</a>) can increase in relative frequency because of the attributes and actions of their sterile relatives (i.e. the “workers” and “warriors”). Darwin even went so far as to indirectly suggest that this is how the cells of a multicellular organism can become specialized for particular traits, even though only the germ cells (i.e. the eggs and sperm cells) reproduce. In both the case of social insects and the case of the cells of a multicellular organism, selection is considered to be operating at the level of groups (Darwin referred explicitly to “families”), rather than strictly at the level of individuals.<br /><br />As we will see in later chapters, the question of what level natural selection operates is of crucial importance to any theory of the evolution of social behavior. It is often asserted that “Darwinian” natural selection can <i>only</i> operate at the level of individual organisms. In other words, populations (i.e. groups) of organisms are what change over time – that is, populations evolve. However, the process by which they evolve – natural selection – occurs when certain individuals with particular traits survive and reproduce more often than others – that is, individuals are selected. As is often asserted by evolutionary biologists: <br /><blockquote><strong><i>Populations</i> evolve,</strong> whereas <strong><i>individuals</i> are selected.</strong></blockquote><br />However, even Darwin himself argued otherwise: that in the social insects (and, by implication, in social animals in general) natural selection can operate at the level of groups as well as at the level of individuals. In later chapters we will explore these ideas in more detail, and will see that there is a resolution to this seeming paradox. As we will see, that resolution is founded on the idea that ultimately <a href="http://en.wikipedia.org/wiki/Gene" target="_blank">genes</a> are what produce the traits of individual organisms. Therefore, <i>natural selection at the level of genes</i> (rather than individuals) can be used as the explanation for the evolution of many social behaviors, especially the evolution of sterile castes in the social insects. <br /><br /><strong>Darwin on the Expression of Emotions in Men and Animals</strong><br /><br />In one of his last books, <a href="http://darwin-online.org.uk/content/frameset?itemID=F1142&viewtype=side&pageseq=1" target="_blank"><i>The Expression of the Emotions in Men and Animals</i></a> (published in 1872) Darwin explored the evolution of behavior in more detail. In it, he elaborated on the idea that behaviors are evolutionary adaptations that have evolved by natural and sexual selection. In particular, he explained the roles that <a href="http://en.wikipedia.org/wiki/Emotion" target="_blank">emotions</a> play in the biology of animals, and extended those explanations to humans. He argued that emotions are essentially biological processes analogous to other anatomical and physiological adaptations, and that the methods by which they can be studied are similar to those by which any other inherited trait can be scientifically analyzed.<br /><br />Darwin used the new technology of photography to illustrate how facial expressions in humans are similar to the facial expressions of other animals in similar situations, such as anger and fear. For example, he argued that the similarities between the “sneer” of a contemptuous human and the raised lips and exposed canine teeth of a snarling dog are not accidental. Both communicate specific states of emotion, and therefore both have adaptive value in the context of social interactions within groups of animals (and, by implication, human social groups). Darwin was essentially making the same argument that <a href="http://en.wikipedia.org/wiki/William_James" target="_blank">William James</a> was to make less than two decades later in his landmark text, <a href="http://psychclassics.yorku.ca/James/Principles/" target="_blank"><i>Principles of Psychology</i></a>; that humans have <i>more</i> instincts than other animals, rather than fewer.<br /><br />In the last chapter of <i>The Expression of the Emotions in Men and Animals</i>, Darwin summarized what he believed to be the three mechanisms by which the expression of emotions in animals and humans have evolved. As he also did in the <i>Origin of Species</i>, Darwin asserted that some emotional expressions are the result of repeated habit that had eventually become hereditary. Again, this is essentially an argument for Lamarckian evolution by means of the inheritance of acquired characteristics. As I have pointed out before, while anatomical and physiological characteristics cannot be passed on in this way, it is possible for behaviors to be acquired and inherited by Lamarckian mechanisms. This would especially be the case if what were inherited (in strictly Darwinian terms) were the tendency to learn a particular behavior in a particular way.<br /><br />Darwin also pointed out that the principle of “antithesis” was central to the communication of emotions and intentions. For example, the facial expressions and body postures that express dominance – <br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuujeU0Adx0edHfKbIw2_x62ipiGAyq9r-CIOtOGBK2WVsepi4viBR0x3bpijFHmmS7yys9C_0xVZOHVxtkOI_URKubQ9GER07mzt29iWYNjrvsQdgirxahghPbADHBJt_Ee76rW5FrW8/s1600-h/Aggressive_Dog.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 236px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuujeU0Adx0edHfKbIw2_x62ipiGAyq9r-CIOtOGBK2WVsepi4viBR0x3bpijFHmmS7yys9C_0xVZOHVxtkOI_URKubQ9GER07mzt29iWYNjrvsQdgirxahghPbADHBJt_Ee76rW5FrW8/s400/Aggressive_Dog.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5316211817376007058" /></a><br />erect hair, forward-pointing ears and directed gaze, stiff and erect posture, etc. – are the antithesis of those that express submission – <br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg15Tz9gZ2yhOMJLu0HL_5y-7R2zgfanT6FohD8gTPrtGERceGWpAXRjOpvrtB3XXzMlqlRE9MrhEzvRcw3cGeTs6dwE0PaXN2784Nv8y4vprAux43vsDrHPJW81W8MT-mAIO2CS2iOcKs/s1600-h/Submissive_Dog.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 216px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg15Tz9gZ2yhOMJLu0HL_5y-7R2zgfanT6FohD8gTPrtGERceGWpAXRjOpvrtB3XXzMlqlRE9MrhEzvRcw3cGeTs6dwE0PaXN2784Nv8y4vprAux43vsDrHPJW81W8MT-mAIO2CS2iOcKs/s400/Submissive_Dog.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5316212202587093650" /></a><br />flattened hair and ears, averted gaze, and downward-curled posture. As we will see later, the expression of emotions and intentions, and the ability to detect these, are central to any understanding of the evolution of human behavior.<br /><br />Throughout most of the <i>Expression of Emotions</i>, Darwin approached the subject of emotional expression as if it were a specialized sub-discipline of anatomy and physiology. For example, Darwin began with a detailed examination of the musculature of the human face<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj_Nqg_rRT1hqvOhAO7jE9kRHarKwAn4wwTw4oPEs1C4WPOMVJ0Sicfq9O98UAuoGHVQUxGwdwMM6Z6jjhVmxQEaivLf0Q4iXvbqMDy0Cg07srz9hLzDswRNxtgzRchJ5OTHyr-ITipQc/s1600-h/Facial_Muscles.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 216px; height: 230px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj_Nqg_rRT1hqvOhAO7jE9kRHarKwAn4wwTw4oPEs1C4WPOMVJ0Sicfq9O98UAuoGHVQUxGwdwMM6Z6jjhVmxQEaivLf0Q4iXvbqMDy0Cg07srz9hLzDswRNxtgzRchJ5OTHyr-ITipQc/s320/Facial_Muscles.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5316212491861095346" /></a><br />showing the various muscles that, when contracted, produce the facial expressions that we associate with particular emotions. Darwin referred to the work of several anatomists and physiologists who had studied the muscles and mechanisms of emotional expression in humans, pointing out the essentially physiological nature of these processes. <br /><br />He then compared the facial expressions of various animals, <br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEHuUg-nVkgjDz-tIorxCTKkqyk0n7Oy9uDNmXDMnmLBnWlBJZz4tosZXbrrLrWzw7ayX_TqO04IQkE4DXft4kfydZP4E-jcZ-lBKWlfNImR1lmbHD_Yb_JLA_Q38tT7A0SKMnxpzPTKQ/s1600-h/Showing_Teeth.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 184px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEHuUg-nVkgjDz-tIorxCTKkqyk0n7Oy9uDNmXDMnmLBnWlBJZz4tosZXbrrLrWzw7ayX_TqO04IQkE4DXft4kfydZP4E-jcZ-lBKWlfNImR1lmbHD_Yb_JLA_Q38tT7A0SKMnxpzPTKQ/s400/Showing_Teeth.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5316212870551825378" /></a><br />including dogs, cats, and the crested macaque (an Indonesian monkey), showing the various similarities in expression of emotion. <br /><br />From his analysis of the expression of emotions in non-human animals, Darwin then went on to examine the expression of emotions in humans. Here, he used the newly developed technology of photography to great effect, presenting photographs of children and adults expressing anxiety, grief, dejection, despair, joy, love, devotion, ill-temper, sulkiness, determination, hatred, anger, disdain, contempt, disgust, quilt, pride, helplessness, patience, puzzlement, surprise, astonishment, fear, horror, shame, shyness, modesty, and included a physiological analysis of blushing. <br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgunv19BySD4pCgAH_STqO0iJRk_WKpPoa2EWmPPkbYai1mJyMuEXTLSspG-O8MfPTcRh9NNTmN0yzCBDYjFvbAHitOe6XURoHUaFiUWWiT-mEhyiRBHLHTTqRjOsY6W9cqjDuzQOap2bs/s1600-h/Human_Faces.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 216px; height: 370px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgunv19BySD4pCgAH_STqO0iJRk_WKpPoa2EWmPPkbYai1mJyMuEXTLSspG-O8MfPTcRh9NNTmN0yzCBDYjFvbAHitOe6XURoHUaFiUWWiT-mEhyiRBHLHTTqRjOsY6W9cqjDuzQOap2bs/s400/Human_Faces.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5316213280803301554" /></a><br /><br />He compared natural expressions with facial expressions produced using electrodes attached to the facial muscles of volunteers. <br /><br />Reading Darwin’s book, it’s clear that he thought of emotions as physiological responses to environmental stimuli. The bulk of the book is taken up with the anatomy and physiology of facial expression via muscle contraction, powered by blood flow through the circulatory system. His intent was and is clear; to show that the capacity for the expression of emotions in animals and people is an evolutionary adaptation, based on what could best be described as physiological processes.<br /><br />Finally, Darwin asserted that much of animal and human behavior is the result of “the direct action of the excited nervous system…independent of the will, and independently…of habit.” In essence, this is an argument against the idea that human behavior is the result of “free will” or conscious intent. Freudian psychology caused a firestorm of controversy in western culture because Freud also suggested that most of human behavior was motivated by drives that were largely unconscious, and therefore not the result of “free will.” Despite a century of research into animal and human behavior, this idea – that our actions are largely not the result of “free will” – is still hugely controversial, even among evolutionary biologists.<br /><br />In the last chapter of <i>The Expression of the Emotions in Men and Animals</i>, Darwin concluded “[t]hat the chief expressive actions, exhibited by man and by the lower animals, are now innate or inherited – that is, have <strong><i>not</i></strong> been learnt by the individual – is admitted by every one.” [<strong><i>Emphasis</i></strong> added] This conclusion would seem to have laid the groundwork for the science we now call evolutionary psychology. Indeed, had evolutionary biologists followed up on Darwin’s suggestions, it is quite possible that a detailed science of evolutionary psychology might have evolved in the first half of the 20th century.<br /><br />However, just the opposite happened – instead of guiding the science of human behavior, Darwin’s theory of evolution by natural selection was eclipsed by a view of human nature that completely rejected any possibility that evolution (or even biology) played any significant role in human psychology. At the same time, a new discipline within the science of evolutionary biology was founded that eventually made it possible for evolutionary psychology to make a new start in the science of human nature. That discipline – <a href="<br />http://en.wikipedia.org/wiki/Population_genetics" target="_blank">theoretical population genetics</a> – will be the subject of the last chapter in this first part of our course on evolutionary psychology.<br /><br /><strong>Essential Reading:</strong><br /><br />Darwin, C. (1859) <i>On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life</i>, 1st ed., Chapter VII: Instinct. John Murray. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=225" target="_blank">here</a>.<br /><br />Darwin, C. (1872) <i>On the Expression of Emotions in Men and Animals</i>. John Murray. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=F1142&viewtype=side&pageseq=1" target="_blank">here</a>.<br /><br /><strong>Supplemental Reading:</strong><br /><br />James, William (1890) <i>Principles of Psychology</i>. Henry Holt. Available online <a href="http://psychclassics.yorku.ca/James/Principles/" target="_blank">here</a>. <br /> <br /><strong>Questions to Consider:</strong><br /><br />1. Can instinctive behaviors have learned components, and vice versa?<br /><br />2. Why did Darwin focus on the expression of emotions when he analyzed the evolution of behavior in humans and other animals? <br /><br />************************************************<br /><br />As always, comments, criticisms, and suggestions are warmly welcomed!<br /><br />--<a href="mailto:adm6@cornell.edu">Allen</a>Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com2tag:blogger.com,1999:blog-854864656386178174.post-10506383039232251512009-02-26T08:12:00.000-08:002009-03-22T18:54:07.277-07:00Ground Rules and Moderation Policy<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvXhGGZrHqk3GulGZot6NXnKR_FfjW1cYhW1S-mY8Rk8aB_u7yaxZl78AryAJSutrRrgs2aAOZOvDhZMYPJBh4lFfVN7eJRSW6gFgCbYzTahxLD9YzLDOOL1y6w9i7pW9BIUPJq1VQ8YQ/s1600-h/Raphael_School_of_Athens.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 261px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvXhGGZrHqk3GulGZot6NXnKR_FfjW1cYhW1S-mY8Rk8aB_u7yaxZl78AryAJSutrRrgs2aAOZOvDhZMYPJBh4lFfVN7eJRSW6gFgCbYzTahxLD9YzLDOOL1y6w9i7pW9BIUPJq1VQ8YQ/s400/Raphael_School_of_Athens.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5307141618810313122" /></a><br /><strong>PURPOSE:</strong> EVOLUTIONARY PSYCHOLOGY is a forum for commentary, discussion, essays, news, and reviews that illuminate the theory of evolution and its implications for psychology in original and insightful ways. <br /><br /><strong>DISCLAIMER:</strong>Unless otherwise noted, all materials may be quoted or re-published in full, with attribution to the author and EVOLUTIONARY PSYCHOLOGY. The views expressed herein do not necessarily reflect those of Cornell University, its administration, faculty, students, or staff.<br /><br /><strong>FORMAT:</strong> Although reading EVOLUTIONARY PSYCHOLOGY is open to everyone, commenting on posts to this blog is entirely moderated. That is, every comment will first be forwarded to the moderator, who will (after due consideration, and working within the constraints of time and work load) decide whether to allow it to be posted to the "Comments" section of the blog.<br /><br /><strong>GROUND RULES:</strong> The founder/moderator of this blog is a great admirer of the traditional values of the academy: collegiality, intellectual freedom, personal responsibility, and respect for others. Therefore, commenting on the posts to this blog has several rules, which will be strictly enforced by the moderator:<br /><br />• <i>Ad hominem</i> attacks, blasphemy, profanity, rudeness, and vulgarity will not be tolerated (although heresy will always be encouraged). However, vigorous attacks against a member's position are expected and those who cannot handle such should think twice before they post a comment.<br /><br />• Long-running debates that are of interest only to a small number of individuals should be taken elsewhere, preferably via private email (i.e. if the moderator gets tired of reading posts concerning the population density [N] of terpsichorean demigods inhabiting ferrous microalpine environments, the posters will be strongly encouraged to settle it outside).<br /><br />• Pseudonyms are tolerated but real names are preferred. However, if the moderator suspects that someone is posting under multiple aliases or pretending to be someone else (i.e. "sock puppeting"), they will be permanently banned from the blog.<br /><br />• Mutual respect and sensitivity towards those with opposing views is essential. In particular, comments containing what the moderator feels is "creation-bashing" by evolutionists or "evolution-bashing" by creationists, will not be approved for posting.<br /><br /><strong>FURTHERMORE:</strong> Both statements of fact and statements of opinion are welcomed, with the following provisos:<br /><br />• Statements of opinion should be clearly indicated as such (perhaps with “IMO” in parenthesis).<br /><br />• Both statements of fact and statements of opinion may be challenged by anyone, so long as the challenge takes place within a reasonable length of time (and please remember, time online passes much more swiftly than time in the real world; three days is a virtual eternity).<br /><br />• If a statement of fact is challenged, the person challenged should make a good faith effort to either provide supporting evidence or make a logical argument as to why such supporting evidence is unnecessary.<br /><br />• No statement may be challenged or attacked by <i>ad hominem</i> arguments or by changing the topic of the thread (i.e. "hijacking"). In particular, anyone directly or indirectly referring to another commentator as either a "liar" or "having lied" (including semantic equivalents, such as "dissembling" or "mendacity") may result in the perpetrator of such an accusation being banned from further participation.<br /><br />• Rather than accusing a commentator of lying when they have made a particular assertion, you should post a rebuttal that documents (with references and pertinent links) that there is evidence that the assertion is false and/or misleading.<br /><br />• Speculation about motives, either directly or indirectly, by anyone commenting on any topic is never allowed and will not be allowed to appear in the "Comments", as this clearly constitutes hijacking the discussion by changing the topic (unless the post itself began as a discussion of motives). If you want to talk about motives, ask the moderator to start a thread to that effect (and if people can't remain civil in the comments on that post, the moderator reserves the right to delete it).<br /><br />• Decisions about moderation are entirely and exclusively the prerogative of the moderator. If you don't want to abide by these rules, please <i>don't</i> waste my time (and yours) by attempting to post or comment here.<br /><br />• Please be aware that <strong><i>any</i></strong> infraction of these rules will result in limitation or rescinding of your commenting privileges. A brief untoward statement in a long and otherwise reasonable comment fully justifies its rejection and may result in the rejection of all your future comments, reasonable or not (so keep backup copies in case you have to try again with a more civil version).<br /><br />• If a post or comment has been rejected by the moderator, please don't repeatedly try to repost them. They won't ever be allowed, it wastes bandwidth and the moderator's time, and simply reinforces the decision on the part of the moderator to reject the post (and maybe ban you permanently).<br /><br />• Appeals of moderation or complaints about the behavior of your fellow commentators are <i>not</i> appropriate on any thread and, even in cases where they are not <i>ad hominem</i> attacks, they still qualify as hijacking the discussion. Any such appeal or complaint should instead be emailed to <a href="mailto:adm6@cornell.edu">the moderator</a>, who will eventually rule one way or the other.<br /><br />************************************************<br /><br />As always, comments, criticisms, and suggestions are warmly welcomed!<br /><br />--<a href="mailto:adm6@cornell.edu">Allen</a>Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com0tag:blogger.com,1999:blog-854864656386178174.post-6383545436989435022009-02-24T07:56:00.000-08:002009-03-22T18:49:23.926-07:00Natural Selection and Evolutionary Adaptations<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4GDo3zQQACkk3SPvoB0yZ7LfpClSmK-ipY2FJKGy8IWNRX-gj6ObrirMe4hZtZ0xqVQ2QLTKwbdU1eLSWYAqvx3hyphenhyphenetIHV1cfgiqs29azmJ1-Cu5nH3D8omfgGDcT2Bhm6EK3CMXppm0/s1600-h/Pocketwatch_Rock.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 241px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4GDo3zQQACkk3SPvoB0yZ7LfpClSmK-ipY2FJKGy8IWNRX-gj6ObrirMe4hZtZ0xqVQ2QLTKwbdU1eLSWYAqvx3hyphenhyphenetIHV1cfgiqs29azmJ1-Cu5nH3D8omfgGDcT2Bhm6EK3CMXppm0/s400/Pocketwatch_Rock.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5306403328005422178" /></a><br /><strong>SUMMARY:</strong><br /><br />Like all of the natural sciences, evolutionary biology is based on the assumption that all natural phenomena can be explained with reference to purely natural causes, and that the simplest explanation for any phenomenon is the best. In particular, most scientists assume that intentions or purposes are not necessary to explain natural phenomena. <br /><br />This assumption is the basis for <a href="http://evolpsychology.blogspot.com/2008/09/natural-selection-darwins-dangerous.html" target="_blank">natural selection</a>, which <a href="http://en.wikipedia.org/wiki/Charles_Darwin" target="_blank">Charles Darwin</a> proposed as the origin of <a href="http://en.wikipedia.org/wiki/Adaptation" target="_blank">adaptations</a>. This means that although adaptations may appear to be purposeful, the processes by which they come about are not. This outlook on the origin of adaptations is particularly important in evolutionary psychology, which is primarily concerned with the behavioral adaptations of humans and related primates. The capacity for human behaviors and motivations is assumed to have evolved by natural and sexual selection, operating in specific ecological contexts in our evolutionary past. A central implication of this view is that adaptations “make sense” only in the context of the evolutionary environment of adaptation.<br /><br /><strong>EVOLUTIONARY PSYCHOLOGY 1.1.4</strong><br /><br />As I stated at the end of the <a href="http://evolpsychology.blogspot.com/2008/09/natural-selection-darwins-dangerous.html" target="_blank">previous chapter</a>, <a href="http://en.wikipedia.org/wiki/Logical_inference" target="_blank">inference</a> is the basis for all reasoning, including scientific reasoning. However, logical inference and arguments by analogy are not necessarily limited to naturalistic explanations. Consider the following:<br /><blockquote>In crossing a health, suppose I pitched my foot against a <i>stone</i>, and were asked how the stone came to be there; I might possibly answer, that, for any thing I knew to the contrary, it had lain there for ever: nor would it perhaps be very easy to show the absurdity of this answer.<br /><br />But suppose I had found a <i>watch</i> upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer which I had before given, that, for any thing I knew, the watch might have always been there. Yet why should not this answer serve for the watch as well as for the stone? Why is it not as admissible in the second case, as in the first?<br /><br />For this reason, and for no other, … that, when we come to inspect the watch, we perceive (what we could not discover in the stone) that its several parts are framed and put together for a purpose… it must have had, for the cause and author of that construction, an artificer, who understood its mechanism, and designed its use. This conclusion is invincible.<br /><br />A <i>second</i> examination presents us with a new discovery. The watch is found, in the course of its movement, to produce another watch, similar to itself; and not only so, but we perceive in it a system or organization, separately calculated for that purpose. What effect would this discovery have, or ought it to have, upon our former inference? What, as hath already been said, but to increase, beyond measure, our admiration of the skill, which had been employed in the formation of such a machine?</blockquote><br />This example of logical inference is taken from the first chapter of <a href="http://darwin-online.org.uk/content/frameset?itemID=A142&viewtype=text&pageseq=1" target="_blank"><i>Natural Theology: or Evidences of the Existence and Attributes of the Deity</i></a>, written by the <a href="http://en.wikipedia.org/wiki/William_Paley" target="_blank">reverend William Paley</a>, an Anglican minister and tutor at Christ's College, Cambridge, in England. Originally published in 1794, it has been continuously in print since then. It went through twenty editions before Paley's death in 1805, and was immensely popular and greatly admired, especially among the faculty and undergraduate students at Cambridge, one of whom had this to say about it:<br /><blockquote>In order to pass the B.A. examination, it was also necessary to get up Paley's <a href="http://www.gutenberg.org/catalog/world/readfile?fk_files=165251" target="_blank"><i>Evidences of Christianity</i></a>…The logic of this book and as I may add of his <i>Natural Theology</i> gave me as much delight as did Euclid. The careful study of these works, without attempting to learn any part by rote, was the only part of the Academical Course which…was of the least use to me in the education of my mind. I did not at that time trouble myself about Paley's premises; and taking these on trust I was charmed and convinced of the long line of argumentation.</blockquote><br />That student, who was so delighted by Paley's writing and charmed by his long line of argumentation, was a mediocre divinity student (and fanatical collector of beetles) by the name of Charles Darwin.<br /><br />As the quotation from Paley's <i>Natural Theology</i> indicates, most people have a "feeling" that nature is designed in some deep way, and that this is somehow connected with religion. And, most religions agree: <br /><blockquote><strong><i>The concept of God goes hand-in-hand with the concept of design in nature. </i></strong></blockquote><br />This is even true for most religions that lack a deity, such as <a href="http://en.wikipedia.org/wiki/Buddhism" target="_blank">Buddhism</a>. Indeed, even many atheists have a “feeling of design” about many things in nature, although they generally do not credit God (or gods) as the author of that design.<br /><br />As we will see, <a href="http://en.wikipedia.org/wiki/Evolutionary_psychology" target="_blank">evolutionary psychology</a> (like evolutionary biology in general) is very much concerned with objects and processes that seem to have a definite purpose. For example, both the existence of fur in mammals and the erection of fur as a warning threat appear to have “purposes”: the first exists in order to keep mammals warm, while the second happens in order to warn other animals that they may be attacked. <br /><br />To a religious believer, both of these characteristics of mammals can be explained as the result of “<a href="http://en.wikipedia.org/wiki/Intelligent_design" target="_blank">intelligent design</a>” on the part of their Creator.” However, as we learned in the previous lecture, one of the most important features of Darwin’s “dangerous idea” is that the theory of evolution by natural selection makes design or purpose in nature unnecessary. <br /><br />As we will see, this is especially true for evolutionary psychology, in which the behaviors and motivations of humans are explained as the result of natural and sexual selection, neither of which are either designed or purposeful. That is, according to evolutionary psychology, a significant part of human behavior is just “doing what comes naturally” – behaving in a way that is not necessarily the result of conscious intentions. <br /><br /><strong>Three Questions: What, How, and Why</strong><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjd274o_79dmCocHEhDMhmWSlJMObhqN4nvyEmUZcqfqgQSEe9HYMB0jqQ-2my8qlutTokVkvpFDxX6RQZsTdEfADp7p9QUdTNpwxImO_mXvIfWZihNFDEqJdJ-gAGQI1hDoprdmdYGFlk/s1600-h/Hand_with_Stone.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 216px; height: 162px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjd274o_79dmCocHEhDMhmWSlJMObhqN4nvyEmUZcqfqgQSEe9HYMB0jqQ-2my8qlutTokVkvpFDxX6RQZsTdEfADp7p9QUdTNpwxImO_mXvIfWZihNFDEqJdJ-gAGQI1hDoprdmdYGFlk/s320/Hand_with_Stone.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5306403947274430626" /></a><br />So, let's return for a moment to reverend Paley's rock (the one he stubbed his toe on while crossing the heath). Consider dropping such a rock: once it leaves your grasp, it falls to the ground. One can ask at least three fundamental questions about this process:<br /><br /><blockquote><strong>Question:</strong> <i>What</i> does the rock do when you drop it? <br /><br /><strong>Answer:</strong> It falls from your hand to the ground.</blockquote><br /> “What” questions are asking for, and are usually answered with a description. Much of what Darwin’s contemporaries did was almost entirely descriptive – they observed nature and described what they saw. This is one reason why what they were doing is often referred to as “natural history” rather than “biological science.”<br /><blockquote><strong>Question:</strong> <i>How</i> does the rock fall to the ground? <br /><br /><strong>Answer:</strong> It falls <i>because</i> of the force of gravity (that is, it falls from your hand to the ground at an accelerating rate that can be described by Newton's Law of Gravity).</blockquote><br />“How” questions are asking for, and are usually answered with an analysis of <i>causes and effects</i> (hence the word “because” in the answer to the “how” question). This is what the natural sciences, and especially the physical sciences such as chemistry and physics, have traditionally been concerned with. An observable phenomenon is analyzed and the mechanisms by which it occurs are determined using controlled experiments. This is what separates “biological science” from “natural history” – the former is much more likely to involve some kind of experimental analysis, while the latter is essentially just descriptive.<br /><br />Just one question left: <br /><blockquote><strong>Question:</strong> <i>Why</i> does the rock fall to the ground?<br /><br /><strong>Answer:</strong> Hmm…</blockquote> <br />This third question is the real kicker, because your answer to it is shaped by a fundamental metaphysical assumption, of which you may or may not be consciously aware. To get at what that assumption is, consider the following statement:<br /><blockquote><strong>Answer:</strong> The rock falls <i>in order to</i> reach the ground.</blockquote><br />Does this explanation make sense? Do you agree or disagree that it makes sense, and if not, why not?<br /><br />The reason that this explanation sounds wrong to most "modern" ears is that included in it is the idea of purpose. Things that happen <i>in order to</i> bring about some end are purposeful things, and rocks (once you have let go of them) are clearly not purposeful things. <br /><br />Or are they? What do we mean when we say that something has a purpose?<br /><br />When we say that some object or event has a purpose, we generally mean that someone (i.e. an "intentional agent") has a pre-existing plan or purpose for that object or event. That is, the object or event exists or takes place because that intentional agent is actively directing it toward some predetermined end. Is that how a dropped rock moves after you have let go of it?<br /><br />Almost everyone would answer "no." Rocks and other inanimate objects can't possibly have intentions or purposes of their own, and when moving (or even sitting still) on their own, their actions or existence is describable using simple physical (or chemical) laws or theories that do not include any kind of intention or purpose.<br /><br /><strong>Ontological Naturalism</strong><br /><br />This way of thinking about reality is known as ontological naturalism, and is central to the way that scientists formulate, test, and interpret explanations about natural processes. Ontological naturalism is based on five primary assumptions:<br /><blockquote>1. Nature (i.e. the universe) contains <i>only</i> energy and matter, and the interactions between these cause <i>all</i> of the observable phenomena in the universe.<br /><br />2. The interactions between energy and matter (and <i>only</i> such interactions) involve the exchange of information.<br /><br />3. Information separate from the interactions of energy or matter <i>cannot</i> be shown to exist (and therefore is generally assumed to not exist).<br /><br />4. The most productive way to analyze the interactions between energy and matter (and the existence of information) is via <i>empirical observation</i> (and therefore the scientific method is the best way to understand nature).<br /><br />5. The simplest explanation of a natural phenomenon is assumed to be the best, until proven otherwise. This is often referred to as <a href="http://en.wikipedia.org/wiki/Occam%27s_razor" target="_blank"><i>Occam’s Razor</i></a>), named in honor of the 14th century English Franciscan friar <a href="http://en.wikipedia.org/wiki/William_of_ockham" target="_blank">William of Ockham</a>, who stated: <i>Pluralitas non est ponenda sine neccesitate</i> – <strong>"Plurality should not be posited without necessity."</strong> In scientific terms, Occam’s Razor says that <i>explanations of natural phenomena should be limited to natural causes.</i></blockquote><br />To these five metaphysical assumptions, nearly all scientists would add a sixth: <br /><blockquote>It is not <i>necessary</i> to assume that intentions or purposes have anything to do with natural phenomena.</blockquote> <br />This last assumption is often extended, as follows: Since purpose in nature is unnecessary to explain natural phenomena, it is assumed that purpose does not exist in natural phenomena. This is why we <i>don't</i> say that dropped rocks fall “in order to” reach the ground.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjaQEHrYYQPd5Tms-Cj2iRANO-Mx3cZTjnX3lAZUk077jXMzz9ifU0iZAkovHqpVCuCqGLTKPXtGgdXKHYKEawiD8IQK19KC3yhRU8ddtUifmETf69ixdls_MZ0jRz-wCmIXZ6WaS_JvN8/s1600-h/Richard_Dawkins.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;width: 216px; height: 265px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjaQEHrYYQPd5Tms-Cj2iRANO-Mx3cZTjnX3lAZUk077jXMzz9ifU0iZAkovHqpVCuCqGLTKPXtGgdXKHYKEawiD8IQK19KC3yhRU8ddtUifmETf69ixdls_MZ0jRz-wCmIXZ6WaS_JvN8/s320/Richard_Dawkins.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5306403449217070738" /></a>As <a href="http://en.wikipedia.org/wiki/Richard_dawkins" target="_blank">Richard Dawkins</a> has pointed out, evolutionary adaptations <i>seem</i> to be the result of purposeful design. In particular, behavioral adaptations seem to be the result of conscious intent. As we will see, there are many animal behaviors (and even some human behaviors) that are neither purposeful nor the result of conscious intent, but rather the simple working out of an adaptation that is the result of natural or sexual selection.<br /><br /><br />To understand how this can be the case, consider the fact (i.e. the observation) that <a href="http://en.wikipedia.org/wiki/Mammal" target="_blank">mammals</a> have fur; is having fur an evolutionary adaptation of mammals? A common way to answer this question is to ask “Does having fur serve some function in mammals?”, which can be simplified to: <br /><blockquote><i>Why</i> do mammals have fur?</blockquote><br />The answer seems simple: <br /><blockquote>Mammals have fur <i>in order to</i> keep warm.</blockquote><br />However, this answer includes the dreaded phrase <i>”in order to”</i>; can the answer be restated in such a way as to remove the implication that fur exists in mammals for a purpose? Yes: <br /><blockquote>Mammals have fur <i>because</i> their parents have fur.</blockquote><br />That is, they inherit from their parents a particular variation that contributed to their ability to survive and reproduce. In long form, the evolutionary answer is: Mammals have fur today because in the past some mammal-like ancestors had fur and some didn’t (i.e. there was variation in the trait of having fur). Those individuals that had fur survived and reproduced more often than those that did not, and so having fur became more common among mammals, until today virtually all mammals have fur.<br /><br />Notice that this means that the answer to the question of <i>why</i> mammals came to have fur is the same as the answer to the question of how mammals came to have fur. In science in general, and evolutionary biology in particular, the answer to the question “why” is the same as the answer to the question “how.” This means that evolutionary adaptations have the appearance of being the result of purpose or intentions, but need not be explained that way. On the contrary, evolutionary biologists explain the existence of seemingly purposeful characteristics of living organisms (i.e. adaptations) as being the result of a process that itself has no purpose (i.e. natural and sexual selection).<br /><br />Given the foregoing, it is easy to see why non-scientists often assume that adaptations “have purposes” and are therefore the result of “intelligent design.” It should also be clear by now why scientists reject this explanation for adaptations, preferring instead the evolutionary explanation proposed by Darwin. That is, the characteristics of organisms we call “adaptations” exist because in the past the individuals who had those characteristics survived and reproduced more often than individuals who did not, and therefore those characteristics have become more common over time.<br /><br /><strong>Evolutionary Implications</strong><br /><br />There are two important implications of the evolutionary viewpoint that we should take note of now, as they will become very important in later chapters: <br /><blockquote>• Given sufficient time for natural and sexual selection to operate, the characteristics we refer to as <a href="http://en.wikipedia.org/wiki/Adaptation" target="_blank">adaptations</a> generally become so common among the individuals that make up what we refer to as a <a href="http://en.wikipedia.org/wiki/Species" target="_blank">species</a> that we say such adaptations are <i>pan-specific</i>. That is, adaptations are generally considered to be present in most of the individuals that make up a species.<br /><br />• However, since natural and sexual selection ultimately depend on variation between individuals in populations, it is equally likely that the degree to which an adaptation is expressed in the individuals in a population is generally not exactly equal. That is, not all individuals will express an adaptation to the same degree, and it may even be virtually absent in some.</blockquote><br />Given the foregoing, how can we tell if a characteristic found among a group of organisms is an evolutionary adaptation? The answer to this question is crucial to the science of evolutionary psychology, as virtually all of evolutionary psychology is directed toward identifying, explaining the existence of, and predicting the effects of human behavioral adaptations.<br /><br />One way to answer this question is to do what most evolutionary biologists do when they observe a particular characteristic of a living organism: ask what the adaptive function of that characteristic is. Paradoxically, this means asking “what is that characteristic <i>for</i>?” which is essentially the same as asking “<i>why</i> does that characteristic exist?” This is sometimes referred to as functional analysis, and as you can see it comes very close to asking what the purpose of the characteristic might be.<br /><br />There is a way to determine whether a given characteristic is an evolutionary adaptation without asking anything about its “purpose.” Since adaptations are understood to be the result of unequal, non-random survival and reproduction, it should be possible to determine if individuals with a characteristic that is suspected to be an adaptation actually survive and reproduce more often than individuals that have either an alternative characteristic or do not express that characteristic as fully. In other words, the “gold standard” in identifying evolutionary adaptations is the observation that the putative adaptation actually results in differential survival and reproduction.<br /><br />As we will see in later chapters, this kind of analysis is very effective at identifying characteristics that are evolutionary adaptations. In some cases, what appear to be evolutionary adaptations clearly are not, as they do not result in differential survival and reproduction. In other cases, characteristics that do not appear to be adaptive can be shown to result in differential survival and reproduction, and so are clearly adaptive despite their appearance.<br /><br />How can behaviors (which leave virtually no fossils and are not anatomical characteristics of animals) possibly qualify as adaptations? In the next chapter, we will see how Darwin argued that some behaviors – what he referred to as “instinct” – can qualify as evolutionary adaptations, and showed how complex behaviors, including some of the behaviors of humans, could be the result of natural and sexual selection, rather than conscious design or intention.<br /><br /><strong>Essential Reading:</strong><br /><br />Dawkins, Richard (1986) <i>The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design</i>. W. W. Norton.<br /><br /><strong>Supplemental Reading:</strong><br /><br />Darwin, C. (1859) <i>On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life</i>, 1st ed. John Murray. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=1" target="_blank">here</a>.<br /><br />Paley, W. (1809) <i>Natural Theology, or Evidences of the Existence and Attributes of the Deity</i>, 12th ed. J. Faulder. 548 pages. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=A142&viewtype=text&pageseq=1" target="_blank">here</a>.<br /><br /><strong>Questions to Consider:</strong><br /><br />1. Is it possible for something to be <i>not</i> random and <i>not</i> purposeful?<br /><br />2. How can one <i>unambiguously</i> determine if something has a purpose, and can this method of determination be applied to natural objects and processes?<br /><br />************************************************<br /><br />As always, comments, criticisms, and suggestions are warmly welcomed!<br /><br />--<a href="mailto:adm6@cornell.edu">Allen</a>Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com3tag:blogger.com,1999:blog-854864656386178174.post-38866454498511891502008-09-28T11:11:00.001-07:002009-03-22T18:55:19.794-07:00Natural Selection: Darwin's Dangerous Idea<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkg2xvia-hgDsPrYy_MmFFKtR30oLcBqnVAZRipAkmKV2F8UchGCdCRSfRNOOKFvlW1LrmReRlPTTZXm61gG0-6WF8TMK05tKRc6SuqP0-ggTr5OFZCtKUEdv62jYHNvK6IuoFYQhU8IU/s1600-h/Origin_of_Species_1859.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkg2xvia-hgDsPrYy_MmFFKtR30oLcBqnVAZRipAkmKV2F8UchGCdCRSfRNOOKFvlW1LrmReRlPTTZXm61gG0-6WF8TMK05tKRc6SuqP0-ggTr5OFZCtKUEdv62jYHNvK6IuoFYQhU8IU/s320/Origin_of_Species_1859.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5251136718123753362" /></a><br /><span style="font-weight:bold;">SUMMARY:</span> <br /><br />Charles Darwin’s theory of evolution by natural selection is both a useful and a “dangerous” idea. This is because Darwin’s theory provides a naturalistic foundation for biology, but also undermines the idea of purpose in nature and the concept of human free will. Darwin proposed two ideas in the Origin of Species: “descent with modification” (what we now call “evolution”) and natural selection (the process by which evolution proceeds). In Darwin’s theory, natural selection is both the “engine” of evolution and the explanation for the origin of adaptations.<br /><br />Darwin’s theory is based on three pre-conditions: <br /><blockquote><strong>Variation</strong> (i.e. differences between individuals in populations),<br /><br /><strong>Inheritance</strong> (from parents to offspring), and <br /><br /><strong>Fecundity</strong> (i.e. the tendency for all organisms to produce more offspring than are necessary to replace themselves).</blockquote> <br />These three pre-conditions entail the following outcome:<br /><blockquote><strong>Natural Selection:</strong> Some individuals survive and reproduce more often than others, and as a consequence their heritable characteristics become more common over time.</blockquote> <br />Central to Darwin’s theory is that it is not necessary to assume that evolution by natural selection has any purpose. Like all natural processes, it proceeds via natural laws that are combinations of chance and necessity alone.<br /><br /><span style="font-weight:bold;">EVOLUTIONARY PSYCHOLOGY 1.1.3</span><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi338dykYiXrn3x-5M9aA9x8TdpZK0smGt3M2gbEG7hy9hMImZo5BeS2sxegdCJCEam34_cL9Bvso2b06BBFF8yhnyxjQF66XRjR5UybTVujRDLwj55qw6thafKeXV8nou5s66EZUeCWhc/s1600-h/Daniel_Dennett.jpg"><img style="float:right; margin:0 0 10px 10px;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi338dykYiXrn3x-5M9aA9x8TdpZK0smGt3M2gbEG7hy9hMImZo5BeS2sxegdCJCEam34_cL9Bvso2b06BBFF8yhnyxjQF66XRjR5UybTVujRDLwj55qw6thafKeXV8nou5s66EZUeCWhc/s320/Daniel_Dennett.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5251137522033593490" /></a><br />Daniel Dennett, a prominent philosopher of science, said this about Darwin's theory of evolution by natural selection:<br /><blockquote>“If I were to give an award for the single best idea anyone ever had, I'd give it to Darwin, ahead of Newton and Einstein and everyone else. In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning, and purpose with the realm of space and time, cause and effect, mechanism and physical law. But it is not just a wonderful scientific idea. <span style="font-weight:bold;">It is a dangerous idea.</span>”</blockquote><br />Darwin's work has had an enormous impact on society, perhaps more than that of any other scientist. His books have changed the world, and will continue to change it for the foreseeable future. His ideas have revolutionized science, and not just biology. By the end of the 20th century, it had become clear to intellectuals in both the sciences and the humanities that the idea of evolution by natural selection could be applied almost without limit to understanding not only life on Earth, but also much of the human condition itself. <br /><br />And therein lies the “danger” to which Dennett alludes, because Darwin’s theory of evolution undermines not only the creation stories central to the world’s dominant religious, it also undermines the very idea of purpose in nature and the concept of human free will. Even atheists have trouble with Darwin’s ideas, especially his idea of natural selection. In this lecture, I intend to show how Darwin’s ideas apply to an understanding of human behavior, and why such ideas might be “dangerous,” and at the same time indispensable to understanding where we have come from and why we do what we do. <br /><br />Darwin’s most famous and most important book was entitled: <i>On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life</i>. At first glance, this seems a typically long-winded Victorian book title, but on closer examination it neatly separates Darwin’s “one long argument” into its two separate but interrelated parts: <br /><blockquote><strong>An argument for the “transmutation of species”</strong> – what Darwin called “descent with modification” and we now refer to as “evolution,” <br /><br />and<br /><br /><strong>An argument for how evolution happens</strong> – natural selection – and how it produces the seemingly purposeful adaptations we see in living organisms.</blockquote><br />At the time of its publication the most immediately controversial idea that Darwin presented in the <i>Origin of Species</i> was the idea that species could change over time. In particular, <span style="font-weight:bold;">Darwin implied </span>(but did not explicitly state in the <span style="font-style:italic;">Origin</span>) <span style="font-weight:bold;">that humans had evolved from “lower forms of life”</span> (ape-like primates, to be exact). <br /> <br />Although in the Origin Darwin merely implied that "Light will be thrown on the origin of man and his history,” both his critics and his supporters immediately began arguing about the evolutionary origins of humans, an argument that Darwin finally addressed twelve years later in <i>The Descent of Man and Selection in Relation to Sex</i>. And not just humans: According to Darwin’s theory, <span style="font-weight:bold;">the diversity of all organisms, living and extinct, could be explained as the result of descent with modification, which Darwin suggested could also be used to revise the taxonomy of life on Earth.</span><br /><br />Almost as controversial at the time of the publication of the <i>Origin</i>, and growing ever more so since then, was Darwin’s proposed mechanism for such evolution – natural selection – according to which, <br /><blockquote><strong>there was no reference to supernatural forces whatsoever</strong>, especially in the first edition,<br /><br />and <br /><br /><strong>blind and purposeless natural forces</strong> – variation, heredity, fecundity, and unequal survival and reproduction – were all that were necessary to explain the extraordinary diversity and adaptive perfection of living systems.</blockquote><br /><br /><span style="font-weight:bold;">DARWIN AND THE <span style="font-style:italic;">ORIGIN OF SPECIES</span></span><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkH_uPKr6D8-61ofcRsFFb04a0Nh_-G_Oo9_W-6g4zGlSpE3F53YKcl6xuPtGPggm6nT1JeWaPmf-rLeWPyeecnC30kcv9_Q_2EqBr2uBAsFNRqsAquM0avPNkqjqyJUNAfeg4SHkFBq0/s1600-h/Gertrude_Himmelfarb.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkH_uPKr6D8-61ofcRsFFb04a0Nh_-G_Oo9_W-6g4zGlSpE3F53YKcl6xuPtGPggm6nT1JeWaPmf-rLeWPyeecnC30kcv9_Q_2EqBr2uBAsFNRqsAquM0avPNkqjqyJUNAfeg4SHkFBq0/s320/Gertrude_Himmelfarb.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5251140387563996178" /></a><br />What makes his accomplishment all the more surprising is that Darwin was not much of a scholar. Indeed, as a young man, Darwin showed almost no interest in academics. Gertrude Himmelfarb, a historian of science who wrote a book about Darwin and the <span style="font-style:italic;">Origin of Species</span> asked:<br /><blockquote><br />“Why was it given to Darwin, less ambitious, less imaginative, and less learned than many of his colleagues, to discover the theory sought after by others so assiduously?"</blockquote><br />According to his autobiography, Darwin studied latin, greek, and mathematics in primary school, but without distinguishing himself as a good student. His greatest interest as a boy was in collecting things – stamps, rocks, birds’ eggs, etc. – and in taking long walks in the country. <br /><br />His primary interests in college were hunting and collecting beetles. His father, a prosperous physician, wanted him to become a doctor (his older brother, Erasmus, was already a doctor), and so sent him to Edinburg University to study medicine with his brother. However, Charles couldn't stand to witness surgery being performed on children without anesthetic, and so he quit medical school. His father then recommended that he become a country parson, so Darwin entered Cambridge University, where he earned a degree in theology. He was, at best, an indifferent student, earning what amounted to a "gentleman's C". <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3zdn3DckKLEyJFDWl7BhtTJ_76sCiLTOFjvsCOU1wgWEBcoJR3D2UfI5GXuY5SF1hVZ_nogRCc3Mmm321e8VMZM711NDbvsMc9jX4DHq2ALYHTuADFYCOocTVX9yDK36j1owQNxSPXgk/s1600-h/Rev._William_Paley.jpg"><img style="float:right; margin:0 0 10px 10px;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3zdn3DckKLEyJFDWl7BhtTJ_76sCiLTOFjvsCOU1wgWEBcoJR3D2UfI5GXuY5SF1hVZ_nogRCc3Mmm321e8VMZM711NDbvsMc9jX4DHq2ALYHTuADFYCOocTVX9yDK36j1owQNxSPXgk/s320/Rev._William_Paley.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5251140897582003810" /></a><br />In later years he said that he had forgotten virtually everything he had learned while at Cambridge, with the exception of two books by William Paley:<br /><blockquote><i>A View of the Evidences of Christianity</i>, in which Paley tried to dismantle David Hume's attack on miracles<br /> <br />and <br /><br /><i>Natural Theology</i>, in which Paley presented the argument for design in nature.</blockquote> <br /><br />So, how could Darwin have written the most important book in biology, if not all of science? There are several aspects of Darwin's character that could explain this apparent anomaly:<br /><blockquote><strong>Darwin was an extraordinarily avid collector, especially of natural objects.</strong> For example, he once tried to capture three beetles (for his collection) by popping one in his mouth and one in each hand. Unfortunately, the one in his mouth exuded an acrid fluid, causing him to drop and lose all three beetles.<br /><br /><strong>Darwin was very deeply interested in geology, as a result of a course he had taken in Cambridge.</strong> It was not uncommon for students in training as parsons to take courses in geology and natural history, as many of them were also amateur naturalists. Darwin showed an unusual interest in geology, which impressed his teacher, Professor Sedgwick, to take him on many field trips throughout England to study the various landforms and rock formations.<br /><br /><strong>Darwin was also very interested in botany and "natural history" (what biology was called in those days).</strong> His botany teacher, Professor Henslow, thought so much of his talents that he recommended that Darwin be appointed as ship's naturalist for the voyage of <i>HMS Beagle</i> (a post Henslow himself had been offered, but turned down due to family responsibilities).</blockquote><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSc71K9SNJpdTQoyTwIQLSV3uODChLFwehAVoHyrRpDPj6wZk2VzjBdqPh6S3JUM6q-l6d7UfoQ_zHOshNjMeGvTwWz-0KF8N56cQAkmPZ9F8pgDGGV46aQ5eidtCtCX6g1ofyBjUNPbc/s1600-h/HMS_Beagle.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSc71K9SNJpdTQoyTwIQLSV3uODChLFwehAVoHyrRpDPj6wZk2VzjBdqPh6S3JUM6q-l6d7UfoQ_zHOshNjMeGvTwWz-0KF8N56cQAkmPZ9F8pgDGGV46aQ5eidtCtCX6g1ofyBjUNPbc/s400/HMS_Beagle.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5251141579892119906" /></a><br />Darwin jumped at the chance to serve as ship's naturalist aboard the <i>Beagle</i>. However, the <i>Beagle's</i> captain, Robert Fitzroy, felt that Darwin was insufficiently qualified for the post, and hired someone else instead. However, Captain Fitzroy did consider Darwin for the position of "gentleman's companion" (someone with whom he could dine and talk who would be of his own social class). At first Fitzroy was reluctant, based on the shape of Darwin's head - Fitzroy was a believer in phrenology, the divining of a person's character and intellect by studying the shape and bumps on a person's head. However, Fitzroy eventually relented, and Darwin was taken on as Fitzroy's companion and amateur naturalist.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAlgstTd9qcFOcoq_8G7-a7bE6n1T-lzkKxrEZzAY4cio3UnN2hyphenhyphenkKSNHAYeazLPWOudpBjJ9vgslwtBA-UC9eQbmkeNvK1IFiP41-XkloCoElyFifPXdSoFZRlnv0SvI0VeO-j0M2xkA/s1600-h/Robert_Fitzroy.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 216px; height: 274px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAlgstTd9qcFOcoq_8G7-a7bE6n1T-lzkKxrEZzAY4cio3UnN2hyphenhyphenkKSNHAYeazLPWOudpBjJ9vgslwtBA-UC9eQbmkeNvK1IFiP41-XkloCoElyFifPXdSoFZRlnv0SvI0VeO-j0M2xkA/s320/Robert_Fitzroy.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5282720488895835442" /></a><br />Darwin's five-year voyage aboard the <i>Beagle</i> transformed him from an indifferent student to a passionate and highly skilled naturalist. He had a natural talent for collecting specimens and recording his observations. He wrote volumes of notes and sent thousands of specimens back to museums in England. His noted eventually became the basis for his first book, <i>A Journal of the Voyages of HMS Beagle</i>, which he wrote with the encouragement of Captain Fitzroy upon his return to England, and which established his reputation as a naturalist among his colleagues. <br /><br />However, Darwin was still essentially a creationist when he returned to England after the voyage of the Beagle. Upon his return, he started several notebooks in which he pondered the things he had observed while on the voyage. Within two years, he had become convinced that “descent with modification” had occurred, but he was at a loss as to how it happened. The crucial turning point in Darwin's thinking came on the evening of <a href="http://evolutionlist.blogspot.com/2008/09/its-darwin-malthus-day.html" target="_blank">28 September 1838</a>, when he read Malthus' <i>Essay on Population</i>. This essay gave him the key to his theory: it suggested a mechanism by which "descent with modification" could occur. It was this mechanism that Darwin eventually called "natural selection" and which he made the basis of his theory of evolution.<br /><span style="font-weight:bold;"><br />Darwin's Conditions for Natural Selection</span><br /><br />Understood correctly natural selection is not itself a mechanism. Rather, it is the <span style="font-weight:bold;">outcome</span> of the operation of three mechanisms:<br /><blockquote><span style="font-weight:bold;">Variety: </span>There are always variations between the characteristics of the members of any population of living organisms. <br />These variations need not be extreme, as illustrated by the relatively large changes that animal and plant breeders have accomplished, using relatively slight differences in physical appearance and behavior among domestic animals and plants.<br /><br /><span style="font-weight:bold;">Heredity: </span>The different variations noted above must be heritable from parents to offspring. Darwin couldn’t propose a mechanism for such inheritance, as none was known at the time. Instead, he simply appealed to the common sense and experience of his readers, counting on them to grant that variations (however acquired) are generally heritable from parents to offspring. <br /><br /><span style="font-weight:bold;">Fecundity: </span>Living organisms have a tendency to produce more offspring than can possibly survive. </blockquote><br />Among those individuals that survive, those that also reproduce pass on to their offspring whatever characteristics made it possible for them to survive and reproduce. This was the missing piece in his theory that Darwin got from his reading of Malthus’ essay on population.<br /><br />Given these three pre-conditions, the following outcome is virtually inevitable:<br /><blockquote><span style="font-weight:bold;">Non-random, unequal survival and reproduction.</blockquote> </span>Survival and reproduction are almost never random. Instead, individuals survive and successfully reproduce at least partly as a result of their characteristics. It is these characteristics that provide the basis for evolutionary adaptations.<br /><br />Darwin had no empirical (i.e. "observational") evidence for natural selection. Instead, he used imaginary examples and analogies to animal and plant breeding. In particular, he began to study the processes of animal and plant breeding very intensively, culminating in an essay that he wrote on the subject in 1842, which he later revised in 1844, and finally published as part of the Origin of Species in 1859.<br /><br />Darwin began the <span style="font-style:italic;">Origin of Species</span> by arguing that the various breeds of domesticated pigeons are analogous to the products of natural selection. He pointed out that all domesticated pigeon breeds are descendants of the wild rock dove (<span style="font-style:italic;">Columba livia</span>). He went on to note that, although "[t]he diversity of the breeds is something astonishing…", they are not separate species. However, they are at least as different from each other as natural species are in the wild. <br /><br />From his interviews with pigeon breeders, Darwin concluded that pigeon breeders of his time believed that all of the various breeds of pigeons were derived from separate kinds of pigeons that existed in the wild. That is, that no evolution or selection had taken place to produce such breeds. Darwin concluded otherwise: that all 700+ breeds of pigeons had been derived from the wild rock dove by means of artificial selection. He asserted that pigeon breeders were denying the evidence right in front of them: that their choices of breeding pairs were shaping the breeds that exist.<br /><blockquote><strong>Darwin asserted that most of the artificial selection done by animal and plant breeders was probably done <i>unconsciously</i>, by breeders choosing desirable traits among their domesticated animals and plants.</strong></blockquote> <br /><br /><span style="font-weight:bold;">Natural Selection and the Problem of Purpose in Nature</span><br /><br />Darwin had two aims in writing the <span style="font-style:italic;">Origin of Species</span>. The first was to convince his readers of the reality of "descent with modification" from common ancestors. He was largely successful in this aim.<br /><br />To accomplish the first aim, Darwin presented an overwhelming mass of evidence from animal and plant breeding, animal behavior, paleontology, biogeography, comparative morphology, classification and taxonomy, and embryology, much of it newly acquired by naturalists from England and other European countries. Many of his readers were avid naturalists themselves, and followed Darwin’s arguments and evidence to their obvious conclusion: that species had indeed changed over time.<br /><br />In terms of the types of logical arguments we discussed in the previous lecture, Darwin’s argument for descent with modification was essentially based on inductive reasoning. He presented multiple, independent, yet similar cases of observable phenomena, all pointing to the same conclusion: that species had gradually descended from previously existing species over long periods of time. Although the evidence could not absolutely prove that evolution had occurred, it was sufficient to convince most of the scientists of his time. <br /><br />Darwin’s second aim – which was much more important to Darwin himself – was to convince his readers that natural selection was the cause of the "beautiful adaptations" that largely define species. He was mostly unsuccessful in this aim.<br /><br />To accomplish his second aim, Darwin was forced to use an argument from analogy, because he could not point to any real-world examples of natural selection in action. In the first chapter of the Origin of Species, he essentially argued that "breeds" under domestication are analogous to "species" in the wild insofar as both are shaped by selection. In other words: <br /><blockquote><strong>Natural selection is analogous to artificial selection</strong>.</blockquote><br />As I discussed in the previous chapter, arguments by analogy – while they are often used – are logically very weak. They depend fundamentally on the validity of the analogy, and are susceptible to subversion if another equally compelling analogy is presented. Historically, this was precisely what happened to Darwin’s proposal of natural selection as the “engine” of descent with modification. <br /><br />To understand why, recall our discussion of the concept of inference from the previous chapter, in which we considered an example of what looked like a house fire. Recall that you didn't actually witness the house fire. All you observed were its effects. What you are doing when you make a guess like this is <span style="font-style:italic;">inferring<span style="font-weight:bold;"></span></span> that an event that you have not actually observed has, in fact, taken place. <br /><br />This is precisely what the theory of evolution does, and when you apply the theory to the natural world, you are using essentially the same reasoning that you would use to decide whether a house fire has happened along the road to work. Lacking direct evidence for natural selection, Darwin argued that its operation could be inferred from observable phenomena. He argued that natural selection is analogous to the artificial selection by which animal and plant breeders had developed the various characteristics of domesticated animals and plants. He also argued that most of this artificial selection had been conducted unintentionally (i.e unconsciously) by animal and plant breeders, thereby suggesting that natural selection could also operate without intentions or purposes.<br /><br />In the <span style="font-style:italic;">Origin</span>, Darwin tried to convince his readers of two propositions: that descent with modification had occurred, and that natural selection was the driving force behind it. Darwin’s argument for descent with modification was based on inductive reasoning. He presented multiple, independent, yet similar cases of observable phenomena, all pointing to the same conclusion: that species had gradually descended from previously existing species over long periods of time. most scientific arguments are grounded in inductive reasoning, he was largely successful in convincing other scientists that descent with modification had occurred.<br /><br />Darwin’s argument for natural selection was largely based on analogy, primarily with artificial selection. Since natural selection was a new idea, there was virtually no actual evidence for or against it when the Origin was published. Instead, Darwin presented an essentially logical argument for natural selection, based on a few largely imaginary examples, and then encouraged his readers to accept the idea on that basis. In doing so, Darwin asked his readers to infer that natural selection was the most likely cause of the evolutionary changes he cited in his argument for descent with modification.<br /><br />The great strength of Darwin’s argument for descent with modification was the huge amount of evidence from natural history that he marshaled to support it. Arguments by induction, while not absolutely conclusive, are extremely powerful, especially in science. The greatest weakness of Darwin’s argument for natural selection was the lack of empirical evidence he could site to support it. Arguments by analogy, while extremely common, have almost no logical force or validity, especially in science.<br /><br />Darwin’s argument for evolution by natural selection was a naturalistic argument. Like virtually all scientific arguments and explanations, it was based on the assumption that the only valid causes for observed effects were those that were entirely limited to natural objects and processes. Central to the naturalistic stance in science is the assumption that natural processes are not intentional; that is, they have no purpose and are not assumed to be the result of intelligent design. is one reason why scientists adopted Darwin’s views so readily: <br /><blockquote><span style="font-weight:bold;"><br />In the <span style="font-style:italic;">Origin of Species</span>, Darwin presented the first fully naturalistic explanation for the evolution of life on Earth.</span></blockquote><br />However, this is also why the theory of evolution by natural selection has met with such intense opposition by non-scientists, and especially religious believers; it ignores (and therefore implicitly negates) any possibility for intentional design or purpose in nature.<br /><br />This conflict between the naturalistic viewpoint shared by virtually all scientists and the “intentional stance” so common among non-scientists (and especially religious believers) is nowhere more intense than in the field of evolutionary psychology. As we will see, evolutionary psychologists assume that much of human behavior is motivated by drives (and even physiological mechanisms) that are largely unconscious, and may even oppose what we perceive to be our conscious desires and intentions.<br /><br />As just one example (which will be discussed in more detail in a later lecture), it has been widely observed that when couples divorce, the husband often remarries a woman much younger than himself, with whom he then has several children. Furthermore, this often happens despite the husband’s lack of obvious intention to start a new family with his new wife. Social scientists often explain this behavior as stemming from economic or social causes, especially the economic disparity between men and women, which makes it much more likely for men to be able to support a new family than their ex-wives.<br /><br />However, this explanation completely ignores the underlying motivations for this pattern of behavior, motivations that become clear only when one views this behavior from an evolutionary perspective. That is, the tendency for men to remarry women younger than themselves is most likely an evolutionary adaptation that is the result of the increased reproductive success that is the result of this behavior.<br /><br />The idea that behaviors, including human behaviors, are evolutionary adaptations that are the result of natural selection is the basis for the science of evolutionary psychology. In the next lecture, therefore, we will take a closer look at what adaptations are and how they can be identified and distinguished from characteristics that are not the result of unequal, non-random survival and reproduction.<br /><span style="font-weight:bold;"><br />Essential Reading:</span><br />Darwin, C. (1859) <span style="font-style:italic;">On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life, 1st ed.</span> John Murray. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=1" target="_blank">here</a>.<br /><br /><span style="font-weight:bold;"><br />Supplemental Reading:</span><br />Barlow, N. (ed.) (1958) <span style="font-style:italic;">The autobiography of Charles Darwin, 1809-1882, with original omissions restored.</span> Collins. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=F1497&viewtype=side&pageseq=1" target="_blank">here</a>.<br /><br />Darwin, C. (1845) <span style="font-style:italic;">Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the Command of Capt. Fitz Roy, R.N. 2d ed.</span> John Murray. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=F14&viewtype=side&pageseq=1" target="_blank">here</a>.<br /><br />Darwin, C. (1871) <span style="font-style:italic;">The descent of man and selection in relation to sex, 1st ed.</span> John Murray. Available online <a href="http://darwin-online.org.uk/content/frameset?itemID=F937.1&viewtype=side&pageseq=1" target="_blank">here</a>.<br /><br />Himmelfarb, G. (1959). <span style="font-style:italic;">Darwin and the darwinian revolution.</span> Doubleday.<br /><br />Malthus, R. T. (1798) <span style="font-style:italic;">An essay on the principle of population.</span> J. Johnson. Available online <a href="<br />http://www.ac.wwu.edu/~stephan/malthus/malthus.0.html" target="_blank">here</a>.<br /><br /><span style="font-weight:bold;">Questions to Consider:</span><br /><br />1. Darwin is often credited with founding the science of biology with his publication of the <i>Origin of Species</i> in 1859. Why is this the case, and do you agree?<br /><br />2. Darwin’s theory of “descent with modification” was accepted by nearly all scientists within a decade of the publication of the <i>Origin of Species</i> in 1859. However, his proposed mechanism of natural selection was not nearly so widely accepted. Why not, and has this situation changed significantly today?<br /><br />************************************************<br /><br />As always, comments, criticisms, and suggestions are warmly welcomed!<br /><br />--<a href="mailto:adm6@cornell.edu">Allen</a>Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com4tag:blogger.com,1999:blog-854864656386178174.post-59892015425470890382008-09-10T07:54:00.001-07:002009-03-22T18:42:20.796-07:00Doing Science: Observation & Inference<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgku1bfMqyVUV0dL5ggfp5Hv7BmTgc6YVTobNOii6YkdPpOx9EZii07fM-zJXk693lL_WthhmmpgqJPaZ__A-1q2AQgkCnVTyNPeUas4NqnYW3TSSp0hFtfocOz83lKDGIKs89nphwY1rQ/s1600-h/house_fire.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgku1bfMqyVUV0dL5ggfp5Hv7BmTgc6YVTobNOii6YkdPpOx9EZii07fM-zJXk693lL_WthhmmpgqJPaZ__A-1q2AQgkCnVTyNPeUas4NqnYW3TSSp0hFtfocOz83lKDGIKs89nphwY1rQ/s320/house_fire.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244417180665072722" /></a><br /><span style="font-weight:bold;">SUMMARY:</span><br /><br />When we encounter something unknown, we try to figure out what it is, how it has come to be that way, and why. Scientists do this by observing nature, a process often called <a href="http://en.wikipedia.org/wiki/Empirical" target="_blank"><span style="font-weight:bold;">empirical analysis<span style="font-style:italic;"></span></span></a>. In many cases (and especially in <a href="http://en.wikipedia.org/wiki/Evolution" target="_blank">evolutionary biology</a>), we can only <a href="http://en.wikipedia.org/wiki/Logical_inference" target="_blank">infer</a> an explanation, because the causes we are interested in cannot be observed directly.<br /><br />The <a href="http://en.wikipedia.org/wiki/Scientific_method" target="_blank"><span style="font-weight:bold;">scientific method<span style="font-style:italic;"></span></span></a> is just common sense, consistently applied. It begins with observations, which are used to formulate a testable <a href="http://en.wikipedia.org/wiki/Hypothesis" target="_blank"><span style="font-weight:bold;">hypothesis<span style="font-style:italic;"></span></span></a>. The hypothesis is then used to formulate a prediction, which is then tested, either via further observations or via a <a href="http://en.wikipedia.org/wiki/Experiment" target="_blank"><span style="font-weight:bold;">controlled experiment<span style="font-style:italic;"></span></span></a>. The results are then compared with the original hypothesis, which may continue to be applied, modified, or even rejected. A <a href="http://en.wikipedia.org/wiki/Theory" target="_blank"><span style="font-weight:bold;">theory<span style="font-style:italic;"></span></span></a> is a hypothesis that has been repeatedly tested and has not yet been shown to be invalid. All scientific theories are therefore open to revision, and none of them are “true” in an absolute sense.<br /><br /><span style="font-weight:bold;">EVOLUTIONARY PSYCHOLOGY 1.1.2</span><br /><br />I began the previous chapter by observing that people are curious about people. While this is undoubtedly the case, it isn't the whole story. We are also extremely curious about the world around us. We (and our primate relatives) are notable among animals for our almost unlimited curiosity. This is especially the case with children, whose curiosity (like a cat's) can sometimes get them into serious trouble. No matter - if we survive a close encounter with something curious, the experience usually pays off. As the German philosopher <a href="http://en.wikipedia.org/wiki/Friedrich_Nietzsche" target="_blank">Friedrich Nietzsche</a> said, “what doesn't kill us makes us stronger.”<br /><br />Once again, <a href="http://en.wikipedia.org/wiki/Evolutionary_psychology" target="_blank">evolutionary psychology</a> is the scientific study of human behavior from an evolutionary perspective. In other words, evolutionary psychologists (just like the rest of us) are curious about what we do and why we do it. As we will see, this curiosity is both useful and dangerous. Useful, because the more we learn about what we do and why we do it, the better able we are to understand our behavior and, if we are lucky, predict it as well. <br /><br />And dangerous, because a scientific understanding of what we do and why we do it undermines some of the most deeply held and passionately defended preconceptions about who we are and why we do what we do. Evolutionary psychology forces us to answer, as carefully and dispassionately as we can, the most fundamental questions every thinking person has ever struggled with:<br /><blockquote><br /><span style="font-weight:bold;">Who are we?</span></blockquote><br /><br /><blockquote><span style="font-weight:bold;">Where have we come from?</span></blockquote><br /><br /><blockquote><span style="font-weight:bold;">Why are we here?</span></blockquote><br /><br /><blockquote><span style="font-weight:bold;">Why do we do what we do?</span></blockquote><br /><br />and<br /><br /><blockquote><span style="font-weight:bold;">How do we know?</span></blockquote><br /><br />The answers that evolutionary psychology gives to these questions may not be what all of us want to hear. But, they have a quality that most of the answers to these questions lack: they can be discovered by simply observing the world around us, and observing ourselves. To see why, let's begin with the last question first.<br /><span style="font-weight:bold;"><br />HOW DO WE KNOW?</span><br /><br />There is a question we need to get out of the way right in the beginning - that is, are the answers that evolutionary psychology provides to those questions "true"? To answer that question, consider the following scenario:<br /><br /><blockquote>It's a Monday morning, and you're running a little late. You rush around doing all of those last-minute things - taking a shower, brushing your teeth, getting dressed, finding your car keys, checking to see if you have everything you need for the day, etc. Then, you dash outside, jump in your car, and head for the freeway…but you don't get very far, because up ahead, the road is blocked off by a cordon of fire trucks and fire fighters, all surrounding what looks like the wreckage of a house fire. [Cue sound effects: distant sirens, people talking in hushed voices, a radio popping and growling, maybe a dog barking, and (for atmosphere) a drizzly rain pattering on the road…or maybe it's just water from the hose that guy is spraying around]</blockquote><br /><br />If you're like almost any human being, you check your headlong rush to elsewhere and rubberneck a little. You drive by slowly as the fire police wave you through, checking out the damage: smelling smoke, hearing the hiss of steam and the growl of the radios, and looking at all of the wreckage.<br /><br />And then, if you're curious, you begin trying to figure out what happened. If you think about it, there are at least three logically consistent answers to the question, "What happened here"?<br /><br /><blockquote>There has been a house fire, which started accidentally.</blockquote> <br /><blockquote><br />There has been a house fire, which was set on purpose. </blockquote><br /><blockquote><br />Someone (perhaps a creative, experienced and well-funded movie director and crew) has just staged what looks like a house fire. </blockquote><br /><br />How can you tell the difference? Consider:<br /><blockquote><br />You did not witness the event (remember, you came on the scene described earlier, after the incident happened). </blockquote><br /><blockquote><br />All that you have available to you is what you can see right now (and hear and touch and so forth). </blockquote><br /><br />To make this more interesting, let's imagine that relatively few of the people standing around saw the actual event either. And, even if they did, you would have to take their word for what they saw (the same would be true for a written account of what happened). Furthermore, the occupants of the house (assuming there were some) aren't around, so they can't tell you what happened either.<br /><br />Given the foregoing, what can you conclude vis-à-vis the three proposed explanations of what happened? Consider the following questions:<br /><br /><blockquote>Can you be <span style="font-weight:bold;">absolutely certain</span> that this situation happened <span style="font-style:italic;">by accident</span>?</blockquote><br /><br /><blockquote>Can you be <span style="font-weight:bold;">absolutely certain</span> that this situation happened <span style="font-style:italic;">on purpose</span>?</blockquote><br /><br /><blockquote>Can you be <span style="font-weight:bold;">absolutely certain</span> that this situation has been <span style="font-style:italic;">staged</span>?</blockquote><br /><br />If you answer these questions with the viewpoint of a scientist, the answer to all three of these questions must be <span style="font-weight:bold;">NO</span>. All you have to go on is what you can observe, and what you observe is compatible with any one of the three explanations proposed.<br /><br />So, how do you decide which to believe?<br /><br />The answer, if you are a scientist, is that you provisionally accept the simplest explanation that best fits all that you have observed and experienced in this event and events like it that you have experienced in the past. If you are lucky, you may never have experienced a house fire yourself. However, you almost certainly have seen the aftermath of one, either directly or in the form of photographs, movies, videos, etc. And so: <br /><blockquote><br />You make your best guess, based on the information available and what you know from past experience.</blockquote><br /><br /><span style="font-weight:bold;">LOGICAL INFERENCE</span><br /><br />What you are doing when you make a guess like this is <span style="font-weight:bold;">inferring<span style="font-style:italic;"></span></span> that an event that you have not actually observed has, in fact, taken place. This is precisely what the <a href="http://en.wikipedia.org/wiki/Theory_of_evolution" target="_blank">theory of evolution</a> does, and when you apply the theory to the natural world, you are using essentially the same reasoning that you would use to decide whether a house fire had occurred before you left your house.<br /><br /><a href="http://en.wikipedia.org/wiki/Logical_inference" target="_blank">Inference</a> is the basis for all reasoning, including scientific reasoning. It's what we will use throughout this series to try to answer the "big questions" we posed at the beginning of this chapter. <br /><br />So, how do evolutionary psychologists use logical inference to figure out what we do and why we do it? We use “common sense,” systematically applied: that is, we use what is often called “the scientific method”.<br /><span style="font-weight:bold;"><br />The Scientific Method</span><br /><br />Evolutionary psychology, like biology, chemistry and physics, is ultimately based on observations: <br /><br /><blockquote>Evolutionary psychology is an <a href="http://en.wikipedia.org/wiki/Empirical" target="_blank"><span style="font-style:italic;">empirical</span></a> science: it is based on observations of the natural world.</blockquote><br /><br />There are non-empirical sciences, such as mathematics and symbolic logic, which are formulated on the basis of abstract principles, usually without direct observation of the real world. However, all of the empirical sciences, including evolutionary psychology, depend fundamentally on observations of objects and processes in nature.<br /><br />Theories in the empirical sciences, including evolutionary psychology, are developed using a logical procedure often called the <a href="http://en.wikipedia.org/wiki/Scientific_method" target="_blank"><br />scientific method</a>. Many people think that the scientific method is similar to magic, or is so difficult to understand and apply that only highly trained scientists can use it. Nothing could be further from the truth:<br /><br /><blockquote>The scientific method is just "common sense" consistently applied. </blockquote><br /><br />In general, the scientific method consists of six or seven steps, always beginning with observations of the real, natural world:<br /><br /><span style="font-style:italic;">Step One: </span>You observe the world around you, focusing your attention on a particular object or process you find interesting:<br /><br /><blockquote><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimxavJKTlHmZbGHaTk_ziYzQHWRUmnQQyBvTYZOKHXWPN15QJmtlbRcCwKD5V32Bwgv-aIPIbc7O35SiADb1hDmyZwo3GA52RJ3YNh5xmmD288Bg2jnXbSn2P0kv_R-2cde9xHlbUzu2A/s1600-h/green_apple.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimxavJKTlHmZbGHaTk_ziYzQHWRUmnQQyBvTYZOKHXWPN15QJmtlbRcCwKD5V32Bwgv-aIPIbc7O35SiADb1hDmyZwo3GA52RJ3YNh5xmmD288Bg2jnXbSn2P0kv_R-2cde9xHlbUzu2A/s320/green_apple.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244422415570930914" /></a><br />For example, if you encounter a green apple growing on an apple tree and you have never eaten an apple before, you might be curious to see what it tastes like. So you try it, and the apple tastes sour.</blockquote><br /><br />What can you conclude about green apples at this point? You might be tempted to say (as many of my students often do), “green apples are sour.” However, recall that this is the very first apple you have ever tasted. Can you, on the basis of a single experience, conclude that “all green apples are sour?”<br /><br />No; in fact, on the basis of this single experience:<br /><blockquote><br />The only <a href="http://en.wikipedia.org/wiki/Theory_of_justification" target="_blank">warranted</a> conclusion (that is, the only conclusion that you can rely on now and in the future) is that “this particular green apple is sour.”</blockquote><br /><br />Don't get me wrong; this isn't absolutely nothing in the way of evidence. At least you know something about this particular apple. However, given your experience, that's all you know. At this point, to extend your observation about this green apple to all green apples would be unwarranted. <br /><br />This is what is known in the empirical sciences as anecdotal evidence:<br /><blockquote><br /><a href="http://en.wikipedia.org/wiki/Anecdotal_evidence" target="_blank"><br />Anecdotal evidence</a> is based on single observations.</blockquote><br /><br />That is, anecdotal evidence, while it may be based on observation, is not logically connected to other, similar observations. Therefore, it cannot and should not be used as the basis for generalizations about nature, at least not in the empirical sciences, where you want to be reasonably certain that your generalizations can help you reliably predict what will happen in the future. <br /><br />So, if you want to learn something about green apples as a class of objects, what do you do next? <br /><br /><span style="font-style:italic;">Step Two:</span> You repeat the experience, attempting to see if a similar event happens as a result.<br /><br /><blockquote><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdzYRx6TmmF-6FjkkGy-cQoUzLtbxojl0Yr1Od2Hpa4NIyJEBrQ_u9sBT_JaOxoYeJggFz9KjdFeXFgwFmx6zKsJzE6RQRh4FQGFEsP_eFpNOigNJ5WPUwxfHBxIjGmEmYKnrnNwja__4/s1600-h/two_green_apples.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdzYRx6TmmF-6FjkkGy-cQoUzLtbxojl0Yr1Od2Hpa4NIyJEBrQ_u9sBT_JaOxoYeJggFz9KjdFeXFgwFmx6zKsJzE6RQRh4FQGFEsP_eFpNOigNJ5WPUwxfHBxIjGmEmYKnrnNwja__4/s320/two_green_apples.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244421989495902018" /></a><br />For example, if after tasting your first green apple you come upon another one, you might be tempted to taste it as well. So (being curious) you do, and the next green apple tastes sour too.</blockquote><br /><br />Can you come to a conclusion about all green apples yet? Well, you might, but to do so would not yet be warranted. Why? Because all you know about so far is that these two similar events seem to be logically connected. Well, how are they connected? Simple: they are similar.<br /><br /><span style="font-weight:bold;">Transductive Reasoning</span><br /><br />Finding similarities between separate events is sometimes referred to as <a href="http://en.wikipedia.org/wiki/Transduction_(psychology)" target="_blank">transductive reasoning</a> (or “transduction”). In other words, <br /><br /><blockquote>Transductive reasoning is formulating a generalization based on an analogy between two apparently similar objects or events.</blockquote><br /><br />Another way of stating this is that: <br /><blockquote><br />Transductive reasoning is <a href="http://en.wikipedia.org/wiki/Argument_by_analogy" target="_blank">arguing by analogy</a>.</blockquote><br />We all use transductive reasoning and transductive arguments all the time. Children in particular use transductive reasoning almost exclusively, as <a href="http://en.wikipedia.org/wiki/Jean_Piaget" target="_blank">Jean Piaget</a> pointed out in his books on child development and learning. As young children we gradually build a "map" of the reality that we experience, using transductive reasoning to relate the objects and processes that we experience to each other.<br /><br />However, from a scientific standpoint, the logical validity of arguments by analogy is extremely weak. This is because such arguments are only as valid as the analogy upon which they are based, and there is no way to establish such validity within the limits of the argument so far. In our example, we may validly state that “this green apple is sour, like that green apple,” but to extend that analogy to all green apples would not be warranted…not yet, anyway.<br /><br />So, how can we strengthen the validity of a generalization based on a single analogy? By repeating it:<br /><br /><span style="font-style:italic;">Step Three: </span>You ask yourself a more general question about what you have observed:<br /><br /><blockquote><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbFSoMCtzUHnz3ltIU5cFg7zFsR7a7f-tEr9bnbuLaFoAMyB7f7z_Kx9JwU-h5vPYMSNJffKL765oR3Uz5SutVaTh8zHjO_bXbxpOvQrMbtsYwE7gr4PbfSQTKIbJ7SHZXdUQ519SlFTQ/s1600-h/green_apples.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbFSoMCtzUHnz3ltIU5cFg7zFsR7a7f-tEr9bnbuLaFoAMyB7f7z_Kx9JwU-h5vPYMSNJffKL765oR3Uz5SutVaTh8zHjO_bXbxpOvQrMbtsYwE7gr4PbfSQTKIbJ7SHZXdUQ519SlFTQ/s320/green_apples.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244424842425379570" /></a><br />You ask the question, "Are <span style="font-style:italic;">all</span> green apples sour?" And then you taste another one, and it's sour too. And then you taste another one, and it's sour as well. And then you taste another and another and another, and they're all sour. </blockquote> <br /><br />Now you're onto something. Rather than having information about a single experience, logically unconnected to anything else, or a single analogy of doubtful validity, you now have information about a logical class of experiences, all connected by similar outcomes. What do you do next?<br /><span style="font-style:italic;"><br />Step Four: </span>You formulate a <a href="http://en.wikipedia.org/wiki/Hypothesis" target="_blank">hypothesis</a>: that is, you formulate a tentative generalization (a “guess,” really) about a class of objects or events, based on the pattern of events that you have observed so far. Based on the foregoing observations, a reasonable hypothesis about green apples would be:<br /><blockquote><br />"Green apples are sour"</blockquote><br /><span style="font-weight:bold;"><br />Inductive Reasoning</span><br /><br />There is a term used to describe the kind of reasoning that scientists use to formulate hypotheses: it is called inductive reasoning (or "induction"). <br /><br /><blockquote><a href="http://en.wikipedia.org/wiki/Inductive_reasoning" target="_blank"><br />Inductive reasoning</a> is formulating a generalization based on a series of individual cases.</blockquote><br /><br />Another way of stating this is that: <br /><blockquote><br />Inductive reasoning is arguing from the particular to the general.</blockquote><br /><br />Inductive reasoning is how virtually all human knowledge and understanding begins. Whenever we encounter a new phenomenon, we try to logically connect it with similar phenomena that we have already experienced. As we do so, we construct larger and larger connected sets of observations about reality (what some educational psychologists call <a href="http://en.wikipedia.org/wiki/Concept_map" target="_blank">concept maps</a>).<br /><br />Notice two things about any conclusions you might formulate using inductive reasoning:<br /><blockquote><br />The validity of any generalization is only as good as the number of similar observations that have been used to formulate that generalization.</blockquote><br /><br />and<br /><br /><blockquote>Regardless of how many observations may have been made, you cannot be absolutely certain that the generalization that you have formulated is universally applicable. </blockquote><br /><br />This is because you can only observe a small subset of all possible cases of whatever it is you are interested in. After all, no matter how many apples you bite, you might not (yet) have tasted a <a href="http://en.wikipedia.org/wiki/Granny_smith" target="_blank">Granny Smith</a> (an apple that tastes sweet when it is still green!)<br /><br /><span style="font-weight:bold;">Prediction</span><br /><br />Up to this point, your reasoning processes have not really been any different than what everyone does all the time. But remember, one of the primary goals of the empirical sciences is to be able to predict the future. So what do you do next? You make a prediction:<br /><br /><span style="font-style:italic;">Step Five: </span>You formulate a <a href="http://en.wikipedia.org/wiki/Prediction" target="_blank">prediction</a>: that is, you formulate a guess about what will happen if you perform another observation, given your generalization:<br /><br /><blockquote><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8_aWEd_9nPPGOAbL5uIhGnx0nIzrmozcx5ystPPpRs4ZqAYvbv2ofxm66yYBGAbO2YAbZNrQ1Tmo-7D70kcFn8IXgfXA-TgpxG8J_QowaK47kYjY7Xhgjxdq4ixlbfr1UViFovhJTIf0/s1600-h/prediction.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8_aWEd_9nPPGOAbL5uIhGnx0nIzrmozcx5ystPPpRs4ZqAYvbv2ofxm66yYBGAbO2YAbZNrQ1Tmo-7D70kcFn8IXgfXA-TgpxG8J_QowaK47kYjY7Xhgjxdq4ixlbfr1UViFovhJTIf0/s400/prediction.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244426899251853490" /></a><br />Your generalization (i.e. hypothesis) is that "green apples are sour." Therefore, a prediction that follows logically from this generalization is "this is a green apple; therefore, it is sour."</blockquote><br /><br /><span style="font-weight:bold;">Deductive Reasoning</span><br /><br />As you might expect, there is also a term used to describe the kind of reasoning that scientists use to formulate predictions based on hypotheses: it is called deductive reasoning (or "deduction"). <br /><br /><blockquote><a href="http://en.wikipedia.org/wiki/Deductive_reasoning" target="_blank">Deductive reasoning </a> is formulating a prediction about a specific case based on a generalization. </blockquote><br /><br />Another way of stating this is that: <br /><br /><blockquote>Deductive reasoning is arguing from the general to the particular.</blockquote><br /><br />Deductive reasoning is how many of us make judgments about the objects and processes we see around us. <a href="http://en.wikipedia.org/wiki/Aristotle" target="_blank">Aristotle</a>, in his work on logic collectively called <a href="http://www.archive.org/details/AristotleOrganon" target="_blank">The Organon</a>, taught that all logic is based on deduction, and showed how logical deductions could be formulated and applied to many situations.<br /><br />However, there are two caveats about any predictions you might formulate using deductive reasoning:<br /><br /><blockquote>The validity of your prediction is only as valid as your generalization. </blockquote><br /><br />If your generalization is based on a small number of individual observations (especially only one), then it is unlikely to be very useful in making predictions that will be supported by further observation.<br /><br /><blockquote>Regardless of how you have formulated your generalization (i.e. your hypothesis), if you do not then test it as rigorously as you can, you haven't really done any science.</blockquote> <br /><br />In fact, you haven't really done anything useful...yet. Even the ancient Greeks used deductive reasoning; what makes the modern scientific method different is what you do next.<br /><span style="font-style:italic;"><br />Step Six: </span>You test your prediction; that is, make further observations that could either confirm or deny the validity of your hypothesis. There are two somewhat different ways to do this:<br /><br /><blockquote>Make some more observations, similar to the ones that led you to formulate your hypothesis in the first place; this is sometimes called <a href="http://en.wikipedia.org/wiki/Discovery_science" target="_blank">discovery science</a>. </blockquote><br /><br />In the case of your green apple hypothesis, this would consist of simply tasting another green apple (or several more - as many as you can stomach).<br /><br /><blockquote>Perform an <a href="http://en.wikipedia.org/wiki/Experiment" target="_blank">experiment</a>. </blockquote><br /><br />This means performing two kinds of observations: an experimental test, where you manipulate the <a href="http://en.wikipedia.org/wiki/Independent_variable" target="_blank">variable</a> that you are testing, and a <a href="http://en.wikipedia.org/wiki/Experimental_control" target="_blank">control test</a>, where you do not manipulate the same variable.<br /><br />In the case of our green apples, there is no experimental or control test. However, in many scientific tests of hypotheses, control tests are used to determine if the variable being manipulated actually affects the outcome.<br /><br /><blockquote>For example, you might have noticed that the grass along the road is often brown and stunted in the early spring. You suspect that this might be due to salt used on the roads during the winter (i.e. your hypothesis is, "Salt causes grass to become brown and stunted"). So, you design an experiment that tests this hypothesis: you grow some grass, and then apply various solutions of salt and water to see if they affect the color and growth of the grass. Your control test would therefore be water without salt, and your experimental tests would be solutions containing increasing concentrations of salt. If the result of your experiment looked like this:</blockquote><br /><blockquote><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTgRUOtdw9gibU8ZnC_GYnqw3bbQ4GDyyaQwwzxiYDYr0atNCjxwu6RHLRL0Zh8hrKtKnHZ-ELRoda7dvCny9StYs6PEf5MFHuVUZ_5HJBtnXc54qt631kQjK8uG1oO1R_lqJJdLVDTkk/s1600-h/grass_pots.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTgRUOtdw9gibU8ZnC_GYnqw3bbQ4GDyyaQwwzxiYDYr0atNCjxwu6RHLRL0Zh8hrKtKnHZ-ELRoda7dvCny9StYs6PEf5MFHuVUZ_5HJBtnXc54qt631kQjK8uG1oO1R_lqJJdLVDTkk/s400/grass_pots.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244430510054356594" /></a></blockquote><br /><br />you would indeed be warranted in concluding that salt does cause grass to become brown and stunted, and since salt is applied to the roads during the winter, you would also be warranted in inferring that road salt was the most likely cause of the brown and stunted grass you observed along the road in the spring.<br /><span style="font-weight:bold;"><br />Inductive Reasoning (Again)</span><br /><br />Note that whichever way you test your prediction (by further observations or by experiment), you are once again using inductive reasoning. This means that all of the conditions listed above still apply:<br /><br /><blockquote>The validity of your conclusions is only as good as the number of similar observations that you have used to test your hypothesis</blockquote><br /><br />and<br /><br /><blockquote>Regardless of how many observations you may have made, you cannot be absolutely certain that the hypothesis that you have tested and confirmed is universally applicable.</blockquote><br /><br /><span style="font-weight:bold;">Acceptance or Rejection of Hypothesis</span><br /><br />We're almost there; just one more step (or two):<br /><br /><span style="font-style:italic;">Step Seven: </span>You compare your test results with the prediction that you made using your hypothesis. <br /><blockquote><br />If the results are pretty close to the ones predicted, then you have <span style="font-style:italic;">validated</span> your hypothesis. </blockquote><br /><br />However, <br /><br /><blockquote>If the results are significantly different from the ones you predicted, you have <a href="http://en.wikipedia.org/wiki/Falsifiability" target="_blank">falsified</a> your hypothesis. </blockquote><br /><br />In this case, you must take one more (and in many ways the most important) step.<br /><br /><span style="font-style:italic;">Step Eight: </span>You modify (or completely reformulate) your hypothesis and repeat all of the steps.<br /><br /><blockquote><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcluNuOb0Ha-f96DXbQwevXaVfD5TkfauZadLd4HgA2dHJ7ky2tQIIndyhMICrXCwxTXZelwAeTNytrHQS6_n0ljYitke49cCACLIsclaNv8v2MQiw4ntKD_UY73I8qOUMpMYUPbISzjc/s1600-h/one_green_apple.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcluNuOb0Ha-f96DXbQwevXaVfD5TkfauZadLd4HgA2dHJ7ky2tQIIndyhMICrXCwxTXZelwAeTNytrHQS6_n0ljYitke49cCACLIsclaNv8v2MQiw4ntKD_UY73I8qOUMpMYUPbISzjc/s320/one_green_apple.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244432048318802866" /></a><br />So, you try one more green apple, and this time you discover it's sweet (it's a Granny Smith)! </blockquote><br /><br />What do you do? You modify your hypothesis: "Most green apples are sour, except for Granny Smith apples." <br /><br />And then you keep on testing...<br /><blockquote><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjoFFwUioKfveiDw-bdA8Igm3mx41gb4Mp6DT_T-ePp3lFk2EpnW1jpd0DHC99H4G9frT1WdMWcU_uC477DUm721b1zBAtxPIEGOKKVfRx7pgUTZsVnwZkCPybMIwr9o2o70UQChuM7h7A/s1600-h/scientific_method.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjoFFwUioKfveiDw-bdA8Igm3mx41gb4Mp6DT_T-ePp3lFk2EpnW1jpd0DHC99H4G9frT1WdMWcU_uC477DUm721b1zBAtxPIEGOKKVfRx7pgUTZsVnwZkCPybMIwr9o2o70UQChuM7h7A/s400/scientific_method.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244432310916641506" /></a></blockquote><br /><span style="font-weight:bold;"><br />Theories, Laws, and Truth in Science</span><br /><br />After a hypothesis has been rigorously tested, how do scientists refer to it? The call it a theory:<br /><blockquote><br />A <a href="http://en.wikipedia.org/wiki/Scientific_theory#Science" target="_blank">theory</a> is a hypothesis that has been repeatedly tested and has not yet been shown to be invalid.</blockquote><br /><br />That is, all of it's predictions have been observed to conform to reality out so far). <br /><br />Notice that many non-scientists (including many journalists and science writers, and virtually all creationists) use the word "theory" to mean what a scientist means when s/he uses the word "hypothesis;" that is, a tentative guess about the way the world works, which has not yet been thoroughly tested. <br /><br />When a scientist uses the word "theory," s/he is generally referring to what a non-scientist would call a <a href="http://en.wikipedia.org/wiki/Scientific_law" target="_blank">scientific law</a>. This difference in usage flows from the tendency of scientists to consider that virtually no scientific principle is ever absolutely and completely confirmed. It's only as good as the experiments that have been done so far to test it. This means that what scientists refer to as "theories" generally have a great deal of evidence backing them up, more than all other alternative explanations. In other words:<br /><blockquote><br />Scientific theories (such as the theory of evolution) are what most non-scientists refer to as "scientific laws".</blockquote><br /><br />One of the most important implications of the foregoing is that nothing is really "true" in science, using the commonly accepted definition of "truth" That is, no scientific theory (i.e. “scientific law”) is always and absolutely "true":<br /><blockquote><br /><span style="font-weight:bold;">All</span> scientific theories are <span style="font-weight:bold;">always</span> open to revision.</blockquote><br /><br />Even a cursory look at the history of science indicates that theories that were once considered "true" are now either highly modified or have been thrown out altogether. <br /><br />So, what is science?<br /><br /><blockquote>Science is our best guess today at how the universe works based on the evidence we have observed so far, unless and until we find out otherwise.</blockquote><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjtkOu_JGxvRoDl2wtNIBm_E_WDjRUnnJysOQmV0yVgUmefl3PsBlcQ0C-fhRWcZ-Lc2yVKLl1DGnYBGOBawHwjt4NK9P0UHRLxOA_RVuiLUJsyYRWIYa-0h7djhFIZp_-OeIUGYgFE92M/s1600-h/doing_science.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjtkOu_JGxvRoDl2wtNIBm_E_WDjRUnnJysOQmV0yVgUmefl3PsBlcQ0C-fhRWcZ-Lc2yVKLl1DGnYBGOBawHwjt4NK9P0UHRLxOA_RVuiLUJsyYRWIYa-0h7djhFIZp_-OeIUGYgFE92M/s400/doing_science.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5244435550772209394" /></a><br /><br /><span style="font-weight:bold;">Essential Reading:</span><br /><br />Popper, Sir Karl (1959) <span style="font-style:italic;">The Logic of Scientific Discovery</span>. <br /><span style="font-weight:bold;"><br />Supplemental Reading:</span><br /><br />Aristotle. <span style="font-style:italic;">The Organon</span>. Available online <a href="http://classics.mit.edu/Aristotle/categories.mb.txt" target="_blank">here</a>.<br /><br />Nietzsche, F. W. (1889) <span style="font-style:italic;">The Twilight of the Gods </span>(<span style="font-style:italic;">Die Götzen-Dämmerung</span>). Available online <a href="<br />http://www.handprint.com/SC/NIE/GotDamer.html" target="_blank">here</a>.<br /><br /><span style="font-weight:bold;">Questions to Consider:</span><br /><br />1. How much of what we know about the world around us do we know directly (i.e. via direct observation) and how much do we know via logical inference?<br /><br />2. What is the scientific definition of “truth” and is there any other kind?<br /><br />************************************************<br /><br />As always, comments, criticisms, and suggestions are warmly welcomed!<br /><br />--<a href="mailto:adm6@cornell.edu">Allen</a>Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com2tag:blogger.com,1999:blog-854864656386178174.post-15611044820698270042008-09-01T18:32:00.000-07:002009-02-26T08:23:29.465-08:00Evolutionary Psychology: A Conceptual History<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyHidXkAq8rLxGNcEBd6WBy16nxRVo2VcwjpHZrUrfEBSAY4WF6nsIcwFAjIPj9HgixaHDV2QxHN_LShduoTAbyv5N3zGTSgJ4DVqtpddGbjZ7t2mlvWb2-puKejiDmThPTseV80KD_Gk/s1600-h/Charles_Robert_Darwin_1809-1882.jpg"><img style="float:left; margin:0 10px 10px 0;cursor:pointer; cursor:hand;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyHidXkAq8rLxGNcEBd6WBy16nxRVo2VcwjpHZrUrfEBSAY4WF6nsIcwFAjIPj9HgixaHDV2QxHN_LShduoTAbyv5N3zGTSgJ4DVqtpddGbjZ7t2mlvWb2-puKejiDmThPTseV80KD_Gk/s320/Charles_Robert_Darwin_1809-1882.jpg" border="0" alt=""id="BLOGGER_PHOTO_ID_5241235993145119442" /></a><br /><span style="font-weight:bold;">SUMMARY:</span><br /><br />Humans are curious creatures. Our curiosity is a characteristic we share with other primates and is a primary reason for our evolutionary success. It is also the basis for the natural sciences, including evolutionary psychology: the study of human behavior from an evolutionary perspective. The goal of evolutionary psychology is to understand both what we do and why we do it.<br /><br />Evolutionary psychology is a synthetic science, uniting the empirical study of human and primate behavior with a theoretical analysis of the evolutionary dynamics by which such behavior has come about. It differs from European psychoanalytic theory, which historically focused on inferring internal motivational states grounded in basic drives such as hunger, fear, and sexuality. It also differs from American behavioral psychology, which focused on behavior without reference to internal motivations or intentions. <br /><span style="font-weight:bold;"><br />EVOLUTIONARY PSYCHOLOGY 1.1.1:</span><br /><br />People are curious about people. We have always been fascinated by what people do and why we do it. Most people are compulsive “people watchers”, beginning in very early infancy and lasting the rest of our lives. We are endlessly attracted to other people, constantly watching them and trying to figure them out. And not just other people: we carefully observe our own behavior, interpreting and anticipating our own actions as avidly as those of the people around us. This curiosity about each other and ourselves is a trait we share with other social animals, especially primates. As we will see, this exaggerated curiosity is not accidental, nor is it necessarily bad. On the contrary, it is one of the central reasons for our success, as individuals and as a species. Curiosity may have killed the cat, but it has more than once saved the lives of our evolutionary ancestors.<br /><br />This series is about the reasons why we are so curious about each other, and what we have learned so far as the result of satisfying that curiosity. The subject of the science of evolutionary psychology is us, and its primary goal is to understand what we do and why we do it. Put in formal terms:<br /><blockquote><span style="font-style:italic;"><span style="font-weight:bold;"><a href="http://en.wikipedia.org/wiki/Evolutionary_psychology" target="_blank">Evolutionary psychology</a></span> is the scientific study of human behavior from an evolutionary perspective.</span></blockquote><br />Evolutionary psychologists observe people very carefully, either directly or by analyzing indirect information such as <a href="http://en.wikipedia.org/wiki/Demography" target="_blank">demographic data</a>. Our work sometimes takes us into the field, observing people in their “natural habitat,” in much the same way that an ornithologist might observe the behavior of an exotic bird. Some evolutionary psychologists also conduct carefully controlled laboratory experiments, although the “laboratory” may be something as simple as a rickety bridge across a gorge on a college campus. In both cases, the intent is to observe people in the same way that animal behaviorists observe members of other species: without biases or preconceptions about what ought to be happening.<br /><br />Evolutionary psychologists also ask people what they are doing and why they are doing it, although as we will see, such self-reporting is often unreliable. This isn’t necessarily bad; even such unreliability can tell us something interesting about human motivations and our capacity for self-deception.<br /><br />Evolutionary psychology is a branch of <a href="http://en.wikipedia.org/wiki/Psychology" target="_blank">psychology</a>, one of the newest branches of one of the oldest of human disciplines. As the name implies, it has its roots in <a href="http://en.wikipedia.org/wiki/Charles_Darwin" target="_blank">Charles Darwin’s</a> theory of <a href="http://en.wikipedia.org/wiki/Evolution" target="_blank">evolution</a> by <a href="http://en.wikipedia.org/wiki/Natural_selection" target="_blank">natural selection</a>. Darwin’s theory gives us a theoretical perspective that makes it possible to ask questions about human behavior that have not been asked in a systematic way before. It also provides a very practical set of experimental and observational techniques that allows us to make predictions about human behavior in specific contexts.<br /><br />What evolutionary psychology does <span style="font-weight:bold;">not</span> do is recycle old ideas about human nature, except insofar as such ideas may coincidentally be based on the unbiased observation of human behavior. Evolutionary psychology is most emphatically <span style="font-weight:bold;">not</span> <a href="http://en.wikipedia.org/wiki/Social_darwinism" target="_blank">social Darwinism</a>, neither in its origins nor in its conclusions. Indeed, I hope you will be surprised at some of the concepts that have come from the scientific study of human behavior from an evolutionary perspective.<br /><br /><span style="font-weight:bold;"><br />Two Approaches to Psychology</span><br /><br />Again, evolutionary psychology is about what we do and why we do it. Psychologists have historically focused on one of these two subjects, often to the exclusion of the other. That is, psychologists have often either focused on external behavior or its internal motivation:<br /><blockquote><span style="font-style:italic;"><span style="font-weight:bold;"><a href="http://en.wikipedia.org/wiki/Behavior" target="_blank">Behavior</a></span> is what an organism <span style="font-style:italic;">does</span>,</span></blockquote><br />whereas<br /><blockquote><br /><span style="font-style:italic;"><span style="font-weight:bold;"><a href="http://en.wikipedia.org/wiki/Motivation" target="_blank">Motivation</a></span> is <span style="font-style:italic;">why</span> an organism does it.</span></blockquote><br />Although this division appears simple, it encapsulates a dichotomy that has split psychology into two often hostile camps for over a century. Essentially, this division is between experimental psychologists who believe that only observable phenomena can be studied using scientific methods, and theoretical psychologists who believe that it is not only possible to infer and thereby study internal motivations and mental states – that is, the “mind” – but that such internal states are the “ultimate” causes of observable behavior. <br /><br />As we will see, this division is often mirrored in evolutionary biology. On one side are the field and laboratory scientists who conduct carefully controlled observations and experiments testing relatively limited hypotheses. On the other are theoreticians who use mathematical and computer models to formulate synthetic theories that are not always amenable to direct empirical testing. <br /><br />Does this mean that these divisions are therefore unbridgeable? If history is any guide, the answer is “no.” In the<span style="font-style:italic;"> <a href="http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=1" target="_blank">Origin of Species</a></span>, Darwin presented a synthetic theory of evolution, in which field and laboratory observations are used as a foundation for inferring an overarching explanation of the causes and consequences of what Darwin called “descent with modification.” Darwin not only presented mountains of evidence showing that evolution had happened, he also provided a testable explanation of the mechanisms that had caused it, an explanation based solely on naturalistic processes. <br /><br />Evolutionary psychology, like evolutionary theory in general, aims for a synthetic theory that includes both rigorous and unbiased observations of human behavior (including an examination of the contexts within which behaviors occur) and an explanation of the underlying causes of those behaviors from the perspective of evolutionary biology. As such, it constitutes what may be the first genuinely unified theory of human behavior, one that is both grounded in direct observation, yet applicable to the many of the most abstract levels of human cognition – such things as epistemology, ethics, and even aesthetics.<br /><br />Many of the explanatory concepts developed by evolutionary psychologists have come from relatively simple observations of people in partially or fully controlled environments – the same kinds of observations made by social psychologists and sociologists, although from a somewhat different perspective. Other concepts have come from answers to questions posed during interviews or on questionnaires. Still others have come from analysis of census data or demographic data collected for other purposes. <br /><br />Some explanatory concepts in evolutionary psychology are derived from general evolutionary theory – that is, from the formal theories of evolutionary biology, abstracted from specific cases. For example, much of what evolutionary biologists have learned about sexual behavior and mating has come from observations that were stimulated by theoretical analyses of the effects of differing amounts of parental investment in offspring. As has often been the case, such abstract theories have suggested empirical tests, which have yielded many interesting (and often surprising) observations and inferences, which have in turn suggested new theoretical analyses.<br /><br />Finally, some explanatory concepts in evolutionary psychology have come from studies of other non-human animals. This strikes some people (and especially some social scientists and humanists) as odd and perhaps leading to invalid conclusions. After all, people are very different from other animals in many respects. While this is true, it ignores a central concept of the natural sciences: <br /><blockquote><br /><span style="font-style:italic;"><span style="font-weight:bold;">Similar causes produce similar effects.</span></span></blockquote><br />In other words, comparative studies of the behavior of other animals in particular contexts can provide remarkable insight into the causes of such behavior. If such causes and contexts also apply to human behavior, then we may infer that similar causes and contexts can indeed be correlated with similar effects.<br /><br />What does this allow us to do? When it works, it allows us to predict the future. This is the underlying goal of all scientific investigation: to understand enough about the causes of natural phenomena to be able to predict – that is anticipate – their effects. And, of course, to satisfy our curiosity…because that is why we are so curious in the first place. Curiosity, like so many other human (and primate) behavioral traits, has adaptive value. Or, as restated in the parlance of evolutionary biology:<br /><blockquote>Individuals who are curious about the behaviors and motivations of others survive and reproduce more often than those who are less curious. </blockquote><br /><br /><span style="font-weight:bold;"><a href="http://en.wikipedia.org/wiki/History_of_psychology" target="_blank">A Brief Conceptual History of Psychology</a></span><br /><br />Psychology as a science is relatively new, compared with many of the other sciences. However, trying to figure out the patterns of human behavior and the reasons for those behaviors predates the origins of civilization:<br /><br />• There are records from Egyptian papyri that indicate that almost four thousand years ago people were thinking about the causes of such psychological conditions as clinical depression. <br /><br />• The <a href="http://en.wikipedia.org/wiki/Dead_sea_scrolls" target="_blank">Dead Sea Scrolls</a>, dating to about 100 years B.C.E., include a description of two different temperaments in humans, an early attempt to find a pattern in the motivations of human behavior. <br /><br />• In China, psychological tests have been part of civil service examinations for centuries. <br /><br />The term “psychology” was first used in its modern sense in 1590 by the German philosopher <a href="http://en.wikipedia.org/wiki/Rudolph_Goclenius" target="_blank">Rudolph Goclenius</a>, who based it on the Greek word psyche, meaning “soul” or “spirit.” From this viewpoint, “psychology” means “knowledge or understanding of the human soul or spirit.” European philosophers and theologians had speculated for millennia on the existence and properties of the “soul”, but in 1672 <a href="http://en.wikipedia.org/wiki/Thomas_Willis" target="_blank">Thomas Willis</a> asserted that the “soul” is a function of the human brain, rather than the heart or some immaterial entity.<br /><br />Psychology as a science can be dated to 1879, when <a href="http://en.wikipedia.org/wiki/Wilhelm_Wundt" target="_blank">Wilhelm Wundt</a> founded a laboratory in Leipzig, Germany to study human behavior and mental states. In 1890, the American educator and psychologist <a href="http://en.wikipedia.org/wiki/William_James" target="_blank">William James</a> published the first edition of his textbook, <span style="font-style:italic;"><a href="http://psychclassics.yorku.ca/James/Principles/" target="_blank">Principles of Psychology</a></span>. In it, James (like Wundt) asserted that human behavior could be analyzed using the methods of the other sciences, and that this is possible because human psychology is a natural phenomenon, rather than something supernatural like “souls”. Inspired at least in part by James’s work, American psychologists founded the <a href="http://en.wikipedia.org/wiki/American_Psychological_Association" target="_blank">American Psychological Association</a> in 1892, basing its practices and philosophy on the experimental approach pioneered by Wundt and James.<br /><br />However, the experimental approach favored by many American psychologists was soon overshadowed by the work of <a href="http://en.wikipedia.org/wiki/Sigmund_Freud" target="_blank">Sigmund Freud</a>, an Austrian physician originally trained in medical neurology. Freud began his professional career using hypnotism to attempt to treat patients with psychological ailments, but moved on to propose a comprehensive theory to explain the underlying causes of human behaviors. <br /><br /><a href="http://en.wikipedia.org/wiki/Psychoanalysis" target="_blank">Freud’s theory of psychoanalysis</a> was based on a unifying idea: that almost all of human behavior was ultimately motivated by unconscious “drives,” such as hunger, thirst, fear, and especially sexuality. Since in Freud’s theories, such drives are unconscious and exist within the “mind” of the individual, they cannot be observed directly at all. Instead, their existence can only be inferred, based on the behavior of the individual whose actions they are supposedly motivating. Furthermore, Freud and many of his followers did not generally attempt to determine if his theories about drives and their implications were supported by observable evidence.<br /><br />During the 20th century, Freud’s theories about the causes of human behaviors dominated the science of psychology in Europe, but in America a very different tradition developed. Called “<a href="http://en.wikipedia.org/wiki/Behaviorism" target="_blank">behaviorism</a>,” the founders of this tradition rejected Freud’s theories about motivation and unconscious mind, and focused instead on behaviors: what animals (including people) do, rather than speculating on why they do it. Behaviorists such as <a href="http://en.wikipedia.org/wiki/Edward_Thorndike" target="_blank">Edward Thorndike</a>, <a href="http://en.wikipedia.org/wiki/John_B._Watson" target="_blank">John B. Watson</a>, and especially <a href="http://en.wikipedia.org/wiki/B._F._Skinner" target="_blank">B. F. Skinner</a> argued that a purely <a href="http://en.wikipedia.org/wiki/Empirical" target="_blank">empirical</a> science of behavior could be developed that could be used to predict (and even to shape) animal and human behavior, without speculating about motivations. <br /><br />However, after a half century of experimental psychology focused almost exclusively on behavior it became increasingly obvious that a full understanding of animal, and especially human behavior required a “theory of mind” – that is, required some theoretical model of how the nervous system produced behaviors, and why specific behaviors were correlated with specific contexts.<br /><br />This revolution in psychology took hold in four places: in linguistics, in computer sciences, in neurobiology, and in the study of animal behavior from an evolutionary perspective. <br /><br />• In linguistics, <a href="http://en.wikipedia.org/wiki/Noam_Chomsky" target="_blank">Noam Chomsky</a> developed a theory of “natural language” which had at its base the idea that human language has a universal “deep structure,” and that the capacity to learn language is therefore innate: all humans are born with the capacity to learn language, without having to be taught. <br /><br />• In computer sciences, the development of information processing programs required a computational architecture that included something like a “mind;” that is, a central processor that integrated inputs (“sensations”) with outputs (“behaviors”). <br /><br />• In <a href="http://en.wikipedia.org/wiki/Neurobiology" target="_blank">neurobiology</a>, investigations of the structure and function of the sensory, nervous, and motor systems of animals (including humans) pointed to a “functional architecture” that both facilitated behavior and constrained it within patterns set by the cellular architecture of the nervous system.<br /><br />• In the study of <a href="http://en.wikipedia.org/wiki/Ethology" target="_blank">animal behavior</a>, empirical studies of how animals learned showed that the “pure” behaviorism of the American school did not explain why different species of animals (and indeed, different sexes and individuals within a species) exhibited different behaviors in specific contexts.<br /><br />Two new disciplines within the science of psychology have grown out of these four traditions: <a href="http://en.wikipedia.org/wiki/Cognitive_psychology" target="_blank">cognitive psychology</a> and <a href="http://en.wikipedia.org/wiki/Evolutionary_psychology" target="_blank">evolutionary psychology</a>. Both of these new disciplines are grounded in the use of the <a href="http://en.wikipedia.org/wiki/Scientific_method" target="_blank">scientific method</a>: they depend upon observations of behavior to infer theories of motivation, and reject introspection as a way of determining why an organism does what it does. And, unlike behaviorism, both disciplines also explicitly infer the existence of internal mental states. <br /><br />Ultimately, I believe that the disciplines of cognitive psychology and evolutionary psychology will eventually merge into a synthetic discipline in which behavior and motivation are both explained with reference to the underlying architecture of the nervous system, within which the mind resides, and which is ultimately shaped by the evolutionary history of our nervous systems. This series is a first look at this evolving synthesis, and at the evidence upon which it is based. <br /><br /><span style="font-weight:bold;">Essential Reading:</span><br /><br />Buss, D. (2004) <span style="font-style:italic;"><a href="http://www.amazon.com/Evolutionary-Psychology-New-Science-Mind/dp/0205483380/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1220327261&sr=8-1" target="_blank">Evolutionary Psychology: The New Science of the Mind,</a></span>, chapter 1: “The Scientific Movements Leading to Evolutionary Psychology.”<br /><br /><span style="font-weight:bold;">Supplemental Reading:</span><br /><br />Barkow, J., Cosmides, L., & Tooby, J. (1992) <span style="font-style:italic;"><a href="http://www.amazon.com/Adapted-Mind-Evolutionary-Psychology-Generation/dp/0195101073/ref=sr_1_2?ie=UTF8&s=books&qid=1220327348&sr=1-2" target="_blank">The Adapted Mind: Evolutionary Psychology and the Generation of Culture,</a></span> chapter 1: “The Psychological Foundations of culture.”<br /><br />Cosmides, L., & Tooby, J. (online) “<a href="http://www.psych.ucsb.edu/research/cep/primer.html" target="_blank">Evolutionary Psychology: A Primer</a>.”<br /><br /><span style="font-weight:bold;">Questions to Consider:</span><br /><br />1. Why might curiosity have been adaptive to our evolutionary ancestors?<br /><br />2. Before beginning this series, what part (if any) do you think evolution has played in human psychology?<br /><br />************************************************<br /><br />As always, comments, criticisms, and suggestions are warmly welcomed!<br /><br />--<a href="mailto:adm6@cornell.edu">Allen</a>Allen MacNeillhttp://www.blogger.com/profile/13692148273564872787noreply@blogger.com5