• What is evolutionary psychology?

    During much of my higher education, I haven’t enjoyed the small-talk question acquaintances invariably ask: what’s your major? Until last May my answer was “psychology”, which led them to instantly conclude I wished to be a clinical therapist, that being the only existing job within the domain of psychology. At that point I would explain my interest in research, my ambition to put people in a giant rat maze and perhaps to shock then with electrodes, for science. In anticipation of these conversations, I much enjoyed being “undeclared” during my sophomore year during which I would tell people I was a freelance learner and that I found majors fascist and suffocating.

    Antisocial cheek notwithstanding, I knew precisely what I wanted to study a full decade before I arrived at university: evolutionary psychology. Whenever I tell someone that, they almost always ask “What is evolutionary psychology”? I suspect this is not an issue for law or med students. Regardless, perhaps an explanation is in order for the curious readers of this network.

    Square one: Darwin
    Evolutionary psychology is a child of evolutionary biology, so we have to start with Darwin’s grand hypothesis. Darwin was the first to observe, document, and articulate that organisms have traits that are heritable and that some traits lead to more surviving offspring than others. These traits become more numerous in a given population and when this happens enough times for enough traits, a species can change into one or more new species. In a high school biology class, the most common examples of such traits are physical characteristics: giraffes with longer necks are able to reach more leaves, and thus bear more offspring than those who are less-well nourished. Moths with coloration similar to local flora are less apt to feed the local bird population and so on. Is that all that we mean by trait? What is a trait?

    Acting out
    A trait is any observable aspect of an organism. This includes structures like bones or gills, but also behavior. Now a given trait might be genetic (and fodder for selection) or not. An amputee is the victim of circumstance, not genetics, even though their phenotype may include one-armed-ness. That said, behaviors are frequently biological traits and it could hardly be otherwise. What good would it be to have wings, and not have the neural control program capable of learning to use them to fly? Why would it matter for a Peacock to have dazzling, iridescent plumage if the peahen could not evolve useful sexual preferences? Even the giraffe’s over-hyped neck would be totally useless if giraffes didn’t also have brains that found leaves to be delicious. In short, animals have a nature. Birds fly, fish swim, and humans  worry about whether the milk has gone bad because they’ve evolved brains that allow them to.

    These are not new observations. Darwin himself wrote about animal and human psychology, primarily in his The Expression of the Emotions in Man and Animals. He noted that human emotions are accompanied by reliable, carefully choreographed patterns of muscle contractions: facial expressions. Even babies born blind and deaf, who’ve never seen a smile or frown, smile and frown when happy and sad. His observation was far-sighted to say the least. The obvious correlation between subjective, situation-dependent feelings and reflexive biological muscle contractions somehow remained controversial, even a century after Darwin.

    The discovery channel
    I claimed above that EP is a child of  evolutionary biology. Part of the proof of that, is that EP grew so organically out of evolutionary biology. The study of animal behavior is called ethology. As post-war ethology gained in methodological sophistication, ethologists couldn’t help but notice that complex animal behaviors were clearly evolutionary adaptations. Ant species each reveal cognitively impressive social behaviors for an animal incapable of what we’d consider to be learning. In his book, Sociobiology, E.O. Wilson  set out to explain how seemingly maladaptive behaviors like altruism could evolve. Wilson was a naturalist who (at the time) specialized in insects, yet his book covered many animals including humans. Academic heavyweights like  Robert Trivers and Richard Dawkins also helped kick-start the sociobiology that would become modern EP- they were (or are) biologists, not psychologists.

    It simply is not possible to study the behavior of animals (including humans) without concluding that many behaviors have been shaped by natural selection, just as physical traits have.

    Evolutionary psychology can be understood as scientific inquiry predicated on just  3 uncontroversial premises:

    1. The mind is what the brain does.

    2. The brain is an organ, like other organs.

    3. Organs are susceptible to natural selection.

    That’s it. Everything else is just details.

    Category: Evolutionary Psychology

  • Article by: Edward Clint

    Ed Clint is a bioanthropology graduate student at UCLA, cofounder of Skeptic Ink, and USAF veteran.
    • gillt


      Interesting blog!

      I come from a genetics background.

      You said EP is the unholy offspring of evolutionary biology. However, it appears EP is only concerned with the part of evolution that involves natural selection and is further only concerned with behavior, mainly human. Is this accurate? For instance, what kind of work is being on non-mammalian or even invertebrate systems?

      • Edward Clint

        Hello gillt!

        Well I never said “unholy” offspring. =)
        re: Natural selection. Well, natural selection is the only way that things like eyeballs, livers, and bones happen; it’s also the only way that complex behaviors happen (in the sense of originate). However, to understand behavior one has to always take into account a species’ environment and developmental influences. Humans appear to have evolved a taste for fats and sugars and for obvious reasons- these were nutritional treasure chests in our distant past. But today those same tastes are maladaptive instead of adaptive because our environment has changed so radically.

        EP’s do focus on human psychology, but one of their primary tools is cross-species comparison. This is a useful kind of analysis because it can help us sort out when a trait evolved (if in fact, it is an adaptive trait) and perhaps under what circumstances.

        For example, G. Parker suggested the hypothesis that testicle size in primates was influenced by sperm competition; That is to say, in polgynous species where females mate with many males, the males have larger testes to produce more sperm who have to compete with the sperm of other males. This hypothesis can tell us something about prototypical human mating strategies- but only if it’s correct. To find out if it’s right, you look at many primates, their respective mating systems, and their testicle sizes. In this case, the hypothesis has been confirmed by the evidence. Harem-based Gorilla societies in which females only mate with one male feature males with (relatively) tiny testicles. Promiscuous chimpanzees where females often have sex with more than one male have relatively huge testes, and so on.

        This is just one example; there is much fascinating research in areas such as morality and coalitional psychology predicated largely on primate and other animal studies.

        My own paper (to be published in Quarterly Review of Biology this December) is a cross-species comparative analysis that includes 11 species including humans, horses, monkeys, rodents and even an invertebrate, the cuttlefish.

    • gillt

      Alleles can become fixed in the population simply due to drift. So it’s incorrect, it would seem, to say natural selection is how all traits “originate.” As we’ve known for a while morphology can evolve neutrally (e.g., human cranial variation) just as is the case with neutral molecular evolution. In fact, most morphological change in closely related species may be neutral (i.e., brownian motion modeling). In fact much of the stasis seen in the fossil record misrepresents random genetic drift and neutral evolution. It’s too bad we can’t access the genomes from fossils.

      Here’s how H. Allen Orr describes it:
      “One of the simplest questions biologists can ask about natural selection has, surprisingly, been one of the hardest to answer: To what degree is it responsible for changes in the overall genetic makeup of a population? No one seriously doubts that natural selection drives the evolution of most physical traits in living creatures—there is no other plausible way to explain such large-scale features as beaks, biceps and brains. But there has been serious doubt about the extent of the role of natural selection in guiding change at the molecular level. Just what proportion of all evolutionary change in DNA is driven, over millions of years, by natural selection—as opposed to some other process?”

      I would farther by saying neutral selection is the dominant mechanism at the molecular level.

      Do you believe color blindness is an adaptive trait and if so why? How about human blood type?

      Gorillas have tiny testes because they have huge muscles. What is the EP interpretation and extrapolation to proto-human mating habits based on body to testicle size ratios? I would guess they fall somewhere between bonobos and chimp behavior if this is the only prior to consider, which it likely isn’t.

      • Edward Clint

        I didn’t say that all change is natural selection. I said that it’s the only explanation there is for complex features- which Orr stipulates to in the quote you provided. It would be silly to think that drift, which operates on individual genes separately, would randomly coordinate dozens or hundreds of genes necessary to the successful formation of an eye (for example). This is an uncontroversial observation from evolutionary biology that I extend to complex behaviors dependent upon sophisticated neural development.

        re: color blindness. Possibly, but I have no strong opinion on the matter.

        Even if gorilla testes size was related to their muscle size (though I don’t believe this is so), it would not explain away the effect which is quite consistent across primates; subsequent research in mammals and birds has found a similar effect whereby mating system (in particular, multipaternity vs alpha parentage) predicts relative testes size. Humans, among primates, have relatively moderately-sized testes- not as big as a chimpanzees nor as small as gorillas.

    • gillt

      The study of evolution isn’t about looking at complex features. That’s the sexy stuff, sure, but not the most important or even most common. In other words evolution doesn’t equal natural selection.

      Edward Clint: “This is an uncontroversial observation from evolutionary biology that I extend to complex behaviors dependent upon sophisticated neural development.”

      But this isn’t the whole story and may even be misleading. For instance, several individual genes are implicated in the evolution of the human lineage: FOXP2, SRGAP, MYH16, HACNS1. SRGAP underwent a simple duplication event that coincides with the expansion of the neocortex and the transition from Australopithecus to Homo. However this gene is also implicated in a range of learning disorders and brain malformations (too much of the gene/protein is a bad thing). I believe learning falls under complex behavior. My point is, a lot of what appears to be complicated at the phenotypic level may actually have non-complex haplotype features which in turn have evolved by completely random events, such as recombination, and unless you can empirically (not hypothetically) show that it conferred some special advantage on individuals within the population you must assume neutral selection, which is the null hypothesis.

      As you mentioned earlier with fats and sugars, the fitness landscape has changed. The take away lesson is that populations are rarely optimized for their environment, so why assume that this was once the case?

      • Edward Clint

        The study of evolution isn’t about looking at complex features.

        For me, it is. All features, complex or not, have to be explicable in terms of natural selection + drift and other factors. For example, let’s say you’re correct about the FOXP2 etc.., coinciding with the expansion of the neocortex. Why was there neocortex to begin with? Why was there cortex? Why was there a FOXP2 gene to be modified? These things all did not exist at one time, and later they did. By random drift? I think not.

        To be honest, I’m not really interested in this argument. Here’s my job: identify something about our psychology that seems to be based in our biology, then try to explain why it exists. Is it an adaptation? Sometimes the answer will be yes, sometimes no. The paper I authored concluded that some 3 decades of research into an adaption fails to prove that the trait is in fact an adaptation. When such a conclusion is reached, I might look for the answer at the mechanism level, perhaps at the level of genes or molecules. What is important to me, is understanding the origin of a trait. I am not a cheerleader for one sort of explanation over another, as you seem to be. I could not care in the slightest if it is adaptation or a non-adaptation explanation. I also could not care less which is “sexier” or more common across the entire phenotype.

        I choose to investigate complex traits because those are the most interesting to me. They are the least understood- fertile ground for exploration.

        The take away lesson is that populations are rarely optimized for their environment, so why assume that this was once the case?

        The nature of selection is that organisms are adapted to conditions in the past. Therefore, the conditions of the past are relevant to understanding present organisms. We could not understand why whales have hipbones without knowing their environment in the past was the land. You are free to search for a drift explanation if you wish.

    • gillt

      To be honest, I’m not really interested in this argument.

      Well then I apologize bothering you with boring arguments. It’s unfortunate that many EvoPsychs think everything that is interesting is an adaptation (see below). So I’m pleasantly surprised that as an Evolutionary Psychologist you also work at the molecular level and likely appreciate the importance of neutral selection and random genetic drift.

      I didn’t mean to imply that FOXP2 is implicated in the expansion of the neocortex. Neanderthals share the human isoform.


      • Edward Clint

        Yes, I think we should be focused on finding the right explanations, whatever the kind that is.

        Probably in a month or two I will post my QRB paper and initiate some discussion that I think you’ll enjoy because it will be about my investigation of a purported adaptation explaining a phenotype (male performance advantage in some spatial ability measurements). I will argue that researchers accepted an adaptationist explanation far too readily and without rigorous testing, and never looked back.

        I also propose that follow-up research should include more cross-species comparative analysis of the sort I did, but also exploration of the mechanism, which is almost surely the neurotransmitters and receptors in the hippocampus which differ by sex for reasons having nothing to do with selection.

        But that’s to come.. thanks for you comments, and stay tuned!

    • Ohh, this is fantastic!! I love that you’re writing about this, because I find EP quite interesting.

      Actually, I’ve written a couple of blog posts (in Spanish) arguing that spandex female heroes with nice cleveages are not the result of a misgynistic industry or anything of the likes, but the works of publicists and marketing guys taking advantage of their audience’s preferences and that it is used both ways!

      There’s always the intrepid, rebellious, charming prince, and no-one is arguing that there’s discrimination or objectifying of men just because they have a standard model for main characters.

      I guess I could translate those someday, and you could tell me how wrong I am getting EP without telling me in the process that I am some kind of immoral, horrible human being just because I have a different perspective!!

      • Thanks, David!

        Many people don’t understand the way advertisers and even movie producers work. Both use focus groups, groups of people who’r supposed to represent the target demographic, to rate their products. They change the products based on feedback people give. In fact many movies have been radically changed simply as a result of negative viewer feedback. So the media producers tend to give us anything we indicate that we will buy or want.

        This might be called the Cosmo effect, after the magazine Cosmopolitan, which every woman I’ve met says is horrible.. but sells incredibly well.. to women.

        This is not to say that the media has no sway. For example, big Hollywood is unlikely to take on projects with unique protagonists or plots merely because they don’t fit some pre-set mold. So films like Napoleon Dynamite, Fargo, and Brokeback Mountain have to be independent films even though they’re all commercial successes which audiences did want to see.

      • mike4ty4

        “There’s always the intrepid, rebellious, charming prince, and no-one is
        arguing that there’s discrimination or objectifying of men just because
        they have a standard model for main characters.”

        That’s because of the different history regarding men vs. women in society. Women have been historically considered second-class. So something which demeans men isn’t considered as anti-male because men have always been the dominant class.

        Personally, I’d argue that such games are not “misogyny” as in “hatred” of women but they reflect the idea that a woman character should be sold based on sexual appeal, or that the primary or a main reason for including a woman character is to add sexual appeal. There might also be some thinking that a woman character cannot be appealing unless they have sexual appeal, which I would contest. Is a male character not interesting to the audience if the audience is male and straight? The problem is if it reduces a woman to a sex object primarily.

        Note also I’m not calling anyone evil :D