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What should evolutionary psychology comprise?

Recently there have been a number of posts and comments on evolutionary psychology. A new paper in PLoS Biology argues that human brain evolution since the “stone age” (really?) has been rapid and multifaceted. And there are renewed calls for evolutionary psychology to change. As usual, John Hawks has a good commentary.

Criticisms of evolutionary psychology have been around for a long time and the criticisms and program offered by Johan Bolhuis and colleagues are not in themselves new. We shouldn’t just assume selection has occurred (although as Hawks notes, simply identifying that populations have grown is not evidence that selection has occurred). But what, exactly, should evolutionary psychology consist of? What should it do?

I think that the problem with evolutionary psychology (EP) is relatively shallow. After all, if we do have species typical (or population typical) behaviours, then they have to have evolved, and this will involve some adaptations. Something like EP must be right. The problems with EP are not unique to EP, but to studies of adaptive behaviour across the board. It is in effect the role that selection itself plays. It’s almost as if because it is evolutionary, it must be natural selection, but as the very founder of the modern Synthesis, R. A. Fisher, wrote in 1930, in the first sentence of his seminal work, The Genetical Theory of Natural Selection, “Natural Selection is not Evolution”. Why? Because selection can cause or retard evolution, and it can cause diversity or cohesiveness in a species or population. Natural selection is, well, it’s natural selection, and as I have argued, it’s not even a mechanism, but an explanatory scheme into which actual mechanisms are placed. The obsession on natural selection is, I think, unwarranted.

Without methodologies (which do exist and are highly mathematical) that can distinguish natural selection from other dynamics of traits in populations (such as ordinary population growth), to call some trait “adaptive” rests very largely on a subjective judgement. Since we are all liable to confirmation bias, we can find things adaptive this way that are simply reinforcing our prior prejudices (in the sense of “pre-judgements”) that some behaviour or trait is the natural outcome of things.

EP is merely the latest incarnation of sociobiology, or social biology, a research program that has been going on since the 1860s (W. R. Greg’s work is mentioned in Darwin’s Descent of Man, ambiguously). Sociobiology, since its inception, has made analogies from distantly related species to ourselves: stamping grounds are the mating grounds of antelope, so why apply them to humans? Pecking orders were observed in flocking birds like chickens, so why apply them to humans? and so on. The initial sociobiology was massively based on analogies chosen because they explicitly or subconsciously supported some prejudice regarding the “normal” social order of humans as understood by 1950s white western males.

We simply cannot divorce our sociobiology from our cultural biases, no matter how hard we try. Not even the most feminist inclined cultural relativist will be able to do this as an act of will. So even though our psychological dispositions evolved, and much of it evolved by adaptation through natural selection to environments, it looks like evolutionary psychology is fated to fail. Or is it?

I want to suggest that if we stop trying to force everything human into the natural selective straitjacket, we might be able to do some EP that is not subjected to as much arbitrary prejudice. The solution is, I think, to ensure that the traits being discussed are not analogised with relatively unrelated traits in other species, but instead to those traits that are closely related, but are in nonhuman species we are more able to separate from our socialised prejudices. In short, Sociobiology Mark 3 should be phylogenetic.

Sociobiology Mark 1 was promiscuously analogous. Sociobiology Mark 2 was hyperadaptationist. Perhaps Mark 3 can step back a bit from these extremes, and in the process learn something about ourselves by studying our relatives. Cultural biases apply less when you are considering the sociobiology of a gibbon, a baboon or a macaque. What is it we have in common with out relatives because they are our relatives and not because they match our prior beliefs about ourselves or the presumption that all evolution is selective?

In phylogenetic systematics (ofen called “cladism” perjoratively), a trait that is shared among members of a monophyletic group (a “clade”) is a homology. It may be shared unchanged (a plesiomorphy) or changed in different taxa (an apomorphy). Both are homologies. Now even when a homology is changed in some species or other, it remains identifiable as a homology. Consider that the third digit of a bird is homologous with the third digit or, say, a human hand, even though they are not very similar in form, function, or size relative tot he rest of the skeleton. We can identify it because it is in the “same” place in development, and draw some conclusions from that based on our overall knowledge of the developmental processes all vertebrates share.

Behaviours are, if inherited by taxa over evolutionary times, homologies too. Each species has its own typical behaviours, which are modulated by environment, culture and contingencies of individual development, but we nevertheless can identify that there is a species-typical mating strategy for gorillas, bonobos and baboons, which is unique in each case but homolgous across the primate family. Likewise, social organisation. We can identify what is common to all members of Primata, and since we are members of Primata too, what is common to us. Once we do that, we can start to look at the ways in which we are unique for those homologies.

For example, our mating strategy is not at all like the dominant male polygyny of gorillas, nor is it much like the polygynandry of the bonobos. Instead, we tend to pair-bond, at least serially, with some sneaky mating. Yet, the underlying biology is much the same – we have strategies to maximise the number of progeny we successfully rear because, well, that’s what evolution requires to continue. Every primate species is social, and every sexual strategy or mating system is designed around the unique traits of the species which are themselves traits adapted to the mating system. The massive sexual dimorphism of gorillas, where an alpha male silverback can outweigh an adult female 2:1 or more, is because competition for mating is fierce and solitary males will challenge for opportunities to mate that are almost (but not quite) all-or-nothing. Some sneaky mating occurs, of course, but even that is fraught with dangers. A silverback’s backhand blow can rupture internal organs.

So humans canot draw analogous inferences from gorillas, chimps or bonobos, our nearest relatives. But we can identify what sorts of behaviours are mating strategies and social organisation by looking at what varies between our sister taxa. This might seem obvious, but only in retrospect. Most of the work done on primate sneaky mating is done on nonhuman primates. Once we identify what the issues are, then we can identify them in humans with less cultural bias. [Incidentally, I hypothesise that overall, the ratio of sneaky matings to “legitimate” matings among primates will be roughly the degree of dimorphism – the closer in size males and females are, the less sneaky mating occurs. Bonobos, whose sexes are almost identical in size, do not compete for mating opportunities because they share territory and are polygynandrist. Humans are likely less sneaky maters than gorillas. I may be wrong about that.]

As I have argued before, a natural classification by homology permits inductive inferences in the absence of specific information about a species. One has a kind of epistemic Chinese Wall, in which one can act as if one knows nothing about the species (in this case, our own) to begin with, and set up the sorts of expectations we might have knowing what we do about the rest of the clade. This is an old strategy, shorn of the phylogenetics. Before Oliver Sachs used the term, Alfred Wallace referred to himself as the “Anthropologist on Mars” when considering humans, and Desmond Morris began his Naked Ape with a similar argument. But employing phylogenetics means that we can do this with some degree of dispassion other than subjective abilities. Then we can look at how these traits are realised, not only in the species as a whole, but in regional populations and subcultures. Phylogeny can act as a contrast space for our investigations.


  1. JGB JGB

    My past experiences with correcting for phylogenetic effects and some recent work really points to some serious limitations with ignoring the possibility of homoplasy in behavior. It tends to evolve far to rapidly and easily. There maybe some useful nuggets to be gleaned, but I think focusing on only shared ancestral behaviors will be of limited utility as a research program.

    • By focusing on the shared behavioural repertoires of the whole clade, you are less likely to encounter homoplasious behaviours. Also, by focusing on the homologies in general, the particular homologs are averaged away, as it were. To even identify that something is a homology you have moved away from the specific character states, and then can evaluate character states as instances of the character.

  2. As I see it, the major problem for EP is in distinguishing between adaptation due to evolutionary change, and adaptation due to learning. From what I have seen thus far, the tendency has been to credit evolutionary change for a lot of what seems more likely to be change due to learning.

    Distinguishing between what is evolved and what is learned will be no easy task. What were very different human cultures have become significantly homogenized as a result of western influence. Such homogenization reduces what can be learned by cross cultural comparisons. Moreover, cognitive science seems to be on a rather sterile path, so it won’t provide a lot of assistance. I am not optimistic about the future of EP.

  3. Bill Morse Bill Morse

    Even as a staunch adaptationist, I can agree that Mark 3 should focus more on generalities than in trying to explain every quirk of human behavior. But you really need to look beyond the primates. As Trivers pointed out in the 1960’s, there are significant similarities between human and bird behavior, especially in species of birds which are monogamous. It would also behoove us to study cichlids. The sine qua non for detecting the influence of selection is convergence. So behaviors that appear across taxa that only share the trait of monogamy should be a prime focus of EP.

    Within the primates, it seems that it might also be useful to focus on those that are monogamous, given the range of social organizations observed and the dependence of behavior on social organization. Thus gibbons would be a good starting point, as they are the most closely related monogamous species.

    As I have noted in other conversations, it would also be interesting to study why all the monogamous primates sing, especially as that behavior is so central to human sociology.

    • Either the traits of cichlids and songbirds matter for understanding humans because they are related to us and we share them from our LCA, or the inferential warrant of extending what we know of them to ourselves is just that we think that is true of us already. It is a purely deductive analogy, not an inductive and ampliative inference. We learn nothing we didn’t already put there. I’ll stick by my programmatic Diktat.

    • AK AK

      I would deprecate the idea that humans are monogamous as a cultural bias.

      Bernard Chapais describes Homo sapiens as “polygynous with an average number of wives close to one”, that is in many (probably most) cultures a man was allowed to have more than one wife, but most didn’t. [Chapais 2010] This appears to have been true of most hunter-gatherer cultures, which represent the main course of human evolution prior to the invention of agriculture perhaps 10,000 years ago. [Gat 2000, 2010]

      Ref’s (& see my earlier comments)

      Gat, A. (2000) The Human Motivational Complex: Evolutionary Theory and the Causes of Hunter-Gatherer Fighting Anthropological Quarterly, 73.1 (2000), 20-34. NED DOI

      Gat, A. (2010) Why War? Motivations for Fighting in the Human State of Nature in Kappeler and Silk 2010

  4. AK AK

    Cultural biases apply less when you are considering the sociobiology of a gibbon, a baboon or a macaque.

    Interesting that you should leave out any great ape from this list.

    The great apes, including Pongo (and Homo), possess a type of neuron called a “spindle or bipolar cell” (technically called von Economo neurons, named after their discoverer) in the frontal cortex, which appears to be unique to this clade (i.e. not including Hylobates). They are also widely thought to uniquely possess “cognitive empathy (the ability to take others’ perspectives)” [Watts 2010], although one source suggests Maccaca might have this feature. [Flack and de Waal 2004]

    Spindle cells show signs of having many more connections than the typical neuron in the brain, and the regions they inhabit are connected with positive and negative reactions to body conditions, food, and social situations, including empathy in humans. [Allman 2010]

    So humans canot draw analogous inferences from gorillas, chimps or bonobos, our nearest relatives. But we can identify what sorts of behaviours are mating strategies and social organisation by looking at what varies between our sister taxa. This might seem obvious, but only in retrospect.

    I strongly recommend reading Bernard Chapais [2008, 2010, or both] on this subject.


    Allman, J.M., Tetreault, N.A., Hakeem, A.Y., Manaye, K.F., Semendeferi, K., Erwin, J.M., Park, S., Goubert, V., Hof, P.R. (2010) The von Economo neurons in frontoinsular and anterior cingulate cortex in great apes and humans Brain Struct Funct (2010) 214:495–517 DOI 10.1007/s00429-010-0254-0

    Chapais, B. (2008) Primeval kinship: how pair-bonding gave birth to human society. Harvard University Press, Cambridge,MA

    Chapais, B. (2010) The Deep Structure of Human Society: Primate Origins and Evolution in Kappeler and Silk 2010

    Flack, J.C., de Waal, F.B.M. (2004) Dominance style, social power, and conflict management. In: Thierry B, Singh M, Kaumanns W (eds) Macaque societies: a model for the study of social organization. Cambridge University Press, Cambridge, pp 157-181

    Kappeler, P.M., Silk, J.B. (2010) Mind the Gap Tracing the Origins of Human Universals Springer Heidelberg Dordrecht London New York ISBN: 978 3 642 02724 6 e ISBN: 978 3 642 02725 3 DOI 10.1007/978 3 642 02725 3

    Watts, D.P. (2010) Dominance, Power, and Politics in Nonhuman and
    Human Primates In: Kappeler and Silk 2010

    P.S. If it looks like I cut&pasted from some source, I did. I’ll leave you to guess what.

    • I did mention bonobos, chimps and gorillas…

      But I was trying to get across that we can make inferences from more distantly related taxa as well, so long as the inferences are only as strong as the closeness of the relationship. I was being subtle…

      • AK AK

        OK, but…

        IMO you’re putting too much importance on “the closeness of the relationship“, at least if you’re talking about ancestry. Cetaceans and Pachyderms have been observed to also have cells resembling von Economo neurons, [Allman et al. 2010] although the chance of inheritance from a common ancestor is very low. Couldn’t we perhaps look for parallels there as well? (I know, we are.)

        I remember I found Ardrey’s proposed parallel between baboons and Australopithecus very convincing when I first heard them, not so much so today, in light of the fact that Great apes all appear to practice female migration while baboons may well practice male migration. (N.B. Chapais would have it that gorillas have pair-bonding similar to human. If Australopithecus actually had major sexual size dimorphism and, presumably, harems as most primates with such dimorphism have, they might also have had pair-bonding of the sort Chapais attributes to gorillas. But see Reno et al. 2010)

        Earlier than that, JWCambellII wrote a column in Analog describing the altruistic risk-taking behavior of dominant male baboons against an intruding leopard. (Unannotated, and AFAIK without peer-reviewed support.) This image has always stuck with me, probably because I read it in my teens, a highly impressionable age.

        But it’s certainly not impossible, or even implausible, that some of our primate relatives may form “opinions” of troop-fellows based on observations of behavior like this. IMO the whole concept of “status” as depending on the “judgments” of fellow members of the social group is woefully unresearched. Plenty of talk about “dominance”, but there seems to be a tacit assumption that it derives entirely from perceived fighting ability, without any reference to more socially abstract behavior.

        But given how much of human behavior seems to be mediated by neural/chemical responses to observations of the environment, IMO the default assumption should be that many aspects of our human concept of “status” are built on pre-existing primate (or even mammalian) foundations.


        Reno, P.L., McCollum, M.A., Meindl, R.S., Lovejoy, C.O. (2010) An enlarged postcranial sample confirms Australopithecus afarensis dimorphism was similar to modern humans Philos Trans R Soc Lond B Biol Sci. 2010 Oct 27;365(1556):3355-63 doi: 10.1098/rstb.2010.0086

  5. B B

    John S. Wilkins:
    Either the traits of cichlids and songbirds matter for understanding humans because they are related to us and we share them from our LCA, or the inferential warrant of extending what we know of them to ourselves is just that we think that is true of us already. It is a purely deductive analogy, not an inductive and ampliative inference. We learn nothing we didn’t already put there. I’ll stick by my programmatic Diktat.

    No, that is an argument from ignorance. The cichlids and the songbirds don’t have to share an LCA to be relevant, they just have to share a behavioral space, which they do. Since your premise is false, your conclusion doesn’t follow. Your programmatic Diktat and two bucks may get you a cup of coffee, but otherwise don’t count for squat. Why don’t you try reading some Trivers and get back to me. Or I can give you the Readers Digest version if you want. But I will tell you that if you don’t know Trivers you have no business in saying anything about EP.

    • Do you suppose I haven’t read Trivers? Or Fox, Tiger and Wilson? My goodness, B, it is exactly that model to which I am objecting. “Behavioural space” is just the problem, not the solution, or rather, it is a deductive model rather than an inductive one. We get nothing more out of it than we put into constructing it. Your objection here amounts to “You are not accepting the view you are not accepting, and you are therefore wrong”.

      • Bill Morse Bill Morse

        Sorry that my previous response was short and unhelpful. The specific statement to which I was objecting was that ” the traits of cichlids and songbirds matter for understanding humans because they are related to us and we share them from our LCA, or the inferential warrant of extending what we know of them to ourselves is just that we think that is true of us already.” I have difficulty accepting the validity of this statement, as it seems to me to excessively downplay the importance of convergence in understanding evolution. The various species of anteaters are remarkable not because they share a LCA (which they do) but because the traits of that LCA have little to do with the traits of the anteaters, which are formed by convergence based on the ecological niche they occupy.

        And when we look at behavior, what we find is remarkable convergence across taxa in behaviors of various species who share a behavioral niche, such as monogamy. This is not a question of what “we think that is true of us already”, but what has been observed of us. So if we want to understand the extent to which EP is useful, we have to start with the behaviors that are universal across taxa among monogamous species. If you think that those who study jealousy in pigeons are just anthropomorphizing human behavior, I will just say that I think that opinion is as unjustified as saying that those who study rabbit reactions to detergents are just anthropomorphizing human behavior- and I don’t think you believe that.

        Note that you still haven’t answered the only difficult question I raised – one that avoids the whole LCA debate – which is why all the monogamous primates sing 🙂

        • I’m not denying there are convergent traits. I am denying that they are the sort of inference license that traditional sociobiologies have assumed. It is too easy to posit them and too hard to test them, and when you have them, it looks like what you have is a direct analogy that licenses nothing but deductive inference.

          And not all singing primates are monogamous. In fact, I don’t think there is a monogamous primate.

        • Bill Morse Bill Morse

          Let me try one more time. Your premise seems to be that phylogenetic proximity should be paramount in explaining behavior, and what I am telling you is that this is not true. What we actually see is that

  6. As someone who has always glibly dismissed EP1 and EP2 as examples of answers in search of questions, I have to say I find your suggestions re. EP3 alarmingly sensible.

    It seems to me, though, that EP3 would still have to overcome the problem of anthropomorphism: how do we know when we are actually observing a shared trait in a clade which includes humans, as opposed to describing behaviours by other species in the clade in human terms? Do chimpanzees, for example, really ‘go to war’?

    (I hadn’t realised that the word ‘cladism’ is seen as pejorative; I don’t think I could ever bring myself to use the phrase ‘phylogenetic systematics’ – even if I could remember it.)

    • Anthropomorphism is a permanent problem. I am suggesting that phylogeny acts to retard it, not eliminate it.

  7. Layperson here.

    When you say that human mating strategy is not at all like the dominant-male polygyny of gorillas, are you saying that the FLDS are not human? Or is there something I should know about gorillas that I don’t?

    (This sounds snarky, but really, I’m just confused. I know I’m ignorant.)

  8. So: no more comparing hypersocial humans with hypersocial termites, then.

    • It probably has little to do with your comment, but I’m always looking for opportunities to remind everybody that human society is far more intricately organized than any termite colony and that that’s a good reason why we shouldn’t use the same term for both varieties of sociability. We don’t leave the egg laying up to one enormous lady in a central chamber; but our interactions are guided by shared understandings, something utterly missing in the pheromone gradients that tie the bugs together. Both human beings and termites make arches, for example, but the termites do so by piling up their shit for some programmed period of time and then sniffing for the next pile of shit and angling the shit pile in that direction. People, in contrast, understand the principle of the thing and build arches using a mental plan since otherwise we’d never get our shit together. We are far more, rather than far less social than ants or termites since our sociability is not simply an emergent consequence of instinctive individual behavior. Even Pavlov understood that human activity depends upon what he called the secondary signalling system of which language is obviously a major part. Whatever Lady Thatcher used to claim when she was queen of the British nest, there is such a thing as society. A termite Lady Thatcher would have more of a point since termites are actually more libertarian than we are. That doesn’t mean that there cannot be a meaningful evolutionary psychology, of course, just that such a discipline needs to take into account the consequences of the development of language and other cultural transmission mechanisms.

  9. Jeb Jeb

    “Before Oliver Sachs used the term, Alfred Wallace referred to himself as the “Anthropologist on Mars” when considering humans, and Desmond Morris began his Naked Ape with a similar argument.”

    Lovejoy makes a nice remark in one of his papers on Lord Monboddo on this subject, or certainly I’ve always read it as such.

    Referring to cartoons etc. of Lord M. with a tail; the symbol of his outsider status, Lovejoy throws away the remark that a tail can sometimes be the most delightful and pleasing of members.

    A most useful appendage.

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