Thursday, February 11, 2010

John Tooby and Leda Cosmides. Why not collaborate?

The Standard Model therefore frees those in the biological sciences to pursue their research in peace, without having to fear that they might accidentally stumble into or run afoul of highly charged social or political issues. It offers them safe conduct across the politicized minefield of modern academic life. This division of labor is, therefore, popular: Natural scientists deal with the nonhuman world and the “physical” side of human life, while social scientists are the custodians of human minds, human behavior, and, indeed, the entire human mental, moral, political, social, and cultural world. Thus, both social scientists and natural scientists have been enlisted in what has become a common enterprise: the resurrection of a barely disguised and archaic physical/mental, matter/spirit, nature/human dualism, in place of an integrated scientific monism. (Barkow, Cosmides, & Tooby, 1992)

In writing the above words, the evolutionary psychologists John Tooby and Leda Cosmides were denouncing an unwritten agreement that had let researchers study everything about our species in biological terms … except the human mind. Concretely, this modus vivendi denied ‘safe conduct’ to those who wanted to investigate genetic influences on the way the mind develops and functions, unless the creature in question was nonhuman.

While attacking these constraints on research, Tooby and Cosmides actually paved the way for a new set of constraints. Academics would be free to study genetic influences on the mind, as long as these influences did not differ from one human population to another. The two evolutionary psychologists saw no problem in this because, in their opinion, there were no population differences to study.

They justified this opinion on two grounds. First, the more complex the adaptation, the more genes it involves, and the more time needed to make all of the right changes to all of the right genes. Therefore, evolution has created only simple traits during the relatively recent presence of modern humans outside Africa (< 50,000 years):

It is no more plausible to believe that whole new mental organs could evolve since the Pleistocene—i.e., over historical time—than it is to believe that whole new physical organs such as eyes would evolve over brief spans. It is easily imaginable that such things as the population mean retinal sensitivity might modestly shift over historical time, and similarly minor modifications might have been made in various psychological mechanisms. However, major and intricate changes in innately specified information-processing procedures present in human psychological mechanisms do not seem likely to have taken place over brief spans of historical time.

… For these and other reasons, the complex architecture of the human psyche can be expected to have assumed approximately modern form during the Pleistocene, in the process of adapting to Pleistocene conditions, and to have undergone only minor modifications since then (Tooby & Cosmides, 1989, p. 34).

There was a second justification for the new modus vivendi. Because the past fifty thousand years have seen our species diversify into a wide range of environments, recent traits would tend to be adaptive in some environments but not in others. And their underlying genetic variants would tend to proliferate in some populations but not in others. Yet such population specificity seems impossible. At almost any genetic marker (blood types, serum proteins, enzymes, mtDNA, etc.), a typical gene varies much more within than between human populations. And this is true not only for large continental populations but also for small local ones. The geneticist Richard Lewontin (1972) concluded that 85% of our genetic variation exists only among individuals and not between ‘races.’

Tooby and Cosmides (1990, p. 35) explicitly referenced Lewontin’s paper when they argued this point:

Human groups do not differ substantially in the types of genes found, but instead only in the relative proportions of those alleles. … What this means is that the average genetic difference between one Peruvian farmer and his neighbor, or one Bornean horticulturist and her best friend, or one Swiss villager and his neighbor, is 12 times greater than the difference between the "average genotype" of the Swiss population and the "average genotype" of the Peruvian population (i.e., the within-group variance is 12 times greater than the between-group variance).

This is true but does not mean what one might think. The same genetic overlap exists not only between populations of one species, like our own, but also between related species, like canids.

[U]sing genetic and biochemical methods, researchers have shown domestic dogs to be virtually identical in many respects to other members of the genus. … there is less mtDNA difference between dogs, wolves and coyotes than there is between the various ethnic groups of human beings, which are recognized as belonging to a single species (Coppinger & Schneider, 1995, p. 32-33).

Nor is it true that genetic influences on behavior evolve over eons of time. As Henry Harpending and Gregory Cochran (2002) pointed out:

Even if 40 or 50 thousand years were too short a time for the evolutionary development of a truly new and highly complex mental adaptation, which is by no means certain, it is certainly long enough for some groups to lose such an adaptation, for some groups to develop a highly exaggerated version of an adaptation, or for changes in the triggers or timing of that adaptation to evolve. That is what we see in domesticated dogs, for example, who have entirely lost certain key behavioral adaptations of wolves such as paternal investment. Other wolf behaviors have been exaggerated or distorted.

The above points are so elementary that it’s a wonder they never crossed the mind of either John Tooby or Leda Cosmides. Or perhaps they did. I remember attending a talk where John Tooby expressed his skepticism about Lewontin’s 1972 paper, saying that within-population genetic variation was inflated by disease polymorphisms and other junk variability. In addition, he had a low opinion of Lewontin, as seen in this exchange in 2000 with Slate editor, Judith Shulevitz:

In the mid-1970's, for example, Gould, Lewontin, and a few others injected heavy-handed moralizing, easy denunciation, the attribution of dubious intellectual genealogies, and an ad hominem attack-style into scientific debate in an effort to settle intellectual disputes by other means.

… The most notorious tactic of Gould, Lewontin, and their allies during the early years was their attempt to drag the ideas they opposed under by manufacturing links to various repugnant doctrines. … More significantly, they did succeed in tarring the revolution in evolutionary biology in the eyes of nonbiologists, together with any serious attempt to think through the relationship between culture, human nature, and human evolution. This has perpetuated the antiquated status quo, during which social scientists have remained wary of the possibility of scientifically mapping human nature, and have remained almost totally ignorant of modern evolutionary biology. The cumulative harvest of suffering from this will not be small.

Why, then, did Tooby and Cosmides accept Lewontin’s findings so uncritically? Or was this acceptance simply window-dressing, an attempt to procure ‘safe conduct’ for their research?

Such a question has no easy answer. By the late 1970s, few academics wished to discuss whether or not human races exist, any more than people of another age wished to discuss whether or not Jesus had a biological father. There was only one acceptable view. The new academic environment thus allowed a lot of dubious ideas on this subject to go unchallenged because challenging them might lead to accusations of racism. Academics became used to having two sets of beliefs: those they really believed and those they believed for convenience sake. Over time, many lost the ability to distinguish between the two.

Well, so Tooby and Cosmides fudged their beliefs a bit. Wasn’t it worth it? Hasn’t the academic environment become much less hostile to research on “the relationship between culture, human nature, and human evolution”?

The answer to the last question is ‘yes’. It’s less clear, however, whether Tooby and Cosmides had anything to do with the improved academic environment. The last quarter of a century has seen broader societal changes that are probably more relevant.

One was the decline of the far left. In the early 1980s, every college in my city had a Marxist-Leninist club. By the end of the decade, they had all disappeared. Marxists had become few and far between even at the university.

A related factor was the aging of the baby-boomer generation. In the early 1980s, every social science department was flush with young people who often had no idea why they were there. By the end of the decade, the baby boomers were gone and enrolment in the social sciences had fallen by over a half. Students also now tended to be more cynical about politics and more narrowly focused on their studies.

Finally, in the mid-1990s, there was the rise of the Internet. It became possible to discuss ideas outside the normal channels of conferences, peer-reviewed journals, and university publishing houses. This freer academic environment gradually replaced the one that had arisen back in the mid-1970s when ideas flowed through fewer channels and were more easily controlled.

I suspect that Tooby and Cosmides deceived themselves in thinking they could obtain a ‘safe conduct’ for their research from the likes of Lewontin and Gould. The only real-world effect of this self-deception has been to make evolutionary psychology subservient to ideas that are, at best, dubious.


Barkow, J.H., Cosmides, L., & Tooby, J. (eds.) (1992). The Adapted Mind. Evolutionary Psychology and the Generation of Culture, New York, Oxford: Oxford University Press.

Coppinger, R., & R. Schneider, Evolution of working dogs, in: J. Serpell (Ed.), The Domestic Dog: Its Evolution, Behaviour and Interactions with People, Cambridge University Press, Cambridge, 1995, pp. 21-47.

Harpending, H. & G. Cochran. (2002). In our genes, Proceedings of the National Academy of Sciences USA, 99(1), 10-12.

Lewontin, R.C. (1972). The apportionment of human diversity. Evolutionary Biology, 6, 381-398.

Tooby, T. & L. Cosmides. (1990). On the universality of human nature and the uniqueness of the individual: the role of genetics and adaptation, Journal of Personality, 58, 17-67.

Tooby, T. & L. Cosmides. (1989). Evolutionary psychology and the generation of culture, Part I. Theoretical considerations, Ethology and Sociobiology, 10, 29-49.


Eugene said...

This comment doesn't pertain to the subject of this particular post, but rather to an earlier post.

Peter I know you've done some research on male/female sex ratios, and the fact that single men currently outnumber single women at all ages.

A news article just came out in the UK Times that I thought might interest you -

"Single men outnumber unmarried women in every age group apart from the over-75s, according to the official statistics on marriage, published yesterday... While the exact causes of the shift are not known, an increase in the proportion of boys born may be a factor."

You might find this piece useful in any future posts that deal with the subject. Thanks

Eugene said...

Sorry the URL is

Tod said...

Interesting about the fall in student numbers affecting the political climate.

Tooby has not changed his tune, he has a book in press called Universal Minds. Geoffrey Miller says evolutionary psychology has "a remarkably strong metatheoretical consensus". Well that is one way of putting it.

Peter Frost said...


Thanks for the lead. I knew that the 'tipping point' had moved up to beyond the age of 40, but I had no idea that it was now as high as 75 years of age! Fertile marriageable women are becoming a scarce resource in almost all developed societies. I'll do an update on this subject in the coming weeks.


In theory, professors become more candid with increasing age (and tenure). In practice, the opposite seems to happen. The most candid academics tend to be graduate students.

Ben10 said...

What a post! you hammered a couple of truthes that needed to be said and it takes gut to do it, especially in a blog with your name on it and especially because you are an academic yourself.

Anonymous said...

¨The only real-world effect of this self-deception has been to make evolutionary psychology subservient to ideas that are, at best, dubious.¨

What you mean is that you disagree with perceived notions of the implications of the findings of evolutionary psychology.

Don´t be so petty. Investigating the truth of human nature does not mean we need to forgo efforts to be civil and moral. In fact, being able to address those things without choosing to believe that we must have them should a more noble and encouraging thought than the mental slavery of dogma.