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The Environment of Evolutionary Adaptedness, over a million years ago in the Pleistocene. A founding myth of evolutionary psychology.

In the future, how will we look at evolution and human behavior? Perhaps we’ll still be looking through the lens of evolutionary psychology, albeit a more “evolved” one than the current variety. Or perhaps there will be a new paradigm.

One thing is sure. Evolutionary psychology, as now defined, is untenable. It suffers from several flawed assumptions:

- Human nature is uniform, except for gender differences. It came into existence over a million years ago during the Pleistocene, in the Environment of Evolutionary Adaptedness (EEA). This was long before modern humans began to spread out of Africa some 40,000 years ago and eventually form the populations we know today.

- Given the complexity of human behavior, its genetic basis could not have changed to any appreciable extent since the Pleistocene.

- All present-day humans are therefore essentially the same. All differences in behavior, personality, and temperament must result from a single human nature responding to different environmental inputs.

These assumptions are false. Human genetic evolution has actually accelerated over the past 40,000 years, and even more so over the past 10,000. The latter period, in particular, was not one of people adapting to new physical environments defined by climate, landscape, and vegetation. People were adapting to new cultural environments defined by social structure, normative behavior, and technology.

Yes, human behavior is complex, and any genetic influences must be correspondingly complex. But these influences can be radically changed by a few point mutations. There’s no need to start from scratch, as John Tooby and Leda Cosmides imply. There may simply be changes to developmental timing, such as an infant’s mental plasticity being extended into older life stages. Or there may be changes to the degree of masculinization or feminization. The possibilities are endless. Again, there is no need to posit a huge number of genetic changes.

Yes, we are adapted to past environments—and not to the present one. And there is often a mismatch between something that made sense in the past and our present reality. But why assume a time gap of over one million years? Is it because the Pleistocene makes an ideal setting for just-so stories?

I suspect there is another, more cynical reason. By placing the evolutionary origins of human nature in the distant past, one avoids the messy reality of differences among current human populations—differences in outlook, personality, time orientation, and behavioral predisposition. The Pleistocene EEA may be a just-so story about the past, but it has also had a real impact on the present. It was part of the deal that made evolutionary psychology possible, in the wake of the firestorm that consumed sociobiology.

Will evolutionary psychology evolve?

A paradigm can evolve. Medicine was a pseudo-science that killed more patients than it cured as late as the 1920s. In the space of a few decades, the situation completely reversed. There have been similar turnarounds in other fields. Alchemy became chemistry, and astrology became astronomy.

Indeed, there have been calls for a rethinking of evolutionary psychology, even from Tooby and Cosmides. “Although the hominid line is thought to have originated on edges of the African savannahs, the EEA is not a particular place or time” (Tooby and Cosmides, 2005, p. 22). It is a composite of whichever selection pressures brought each adaptation into existence. There are thus potentially as many EEAs as there are adaptations, and some may be later than others.

This year, several evolutionary psychologists authored what may be called a manifesto for change:

We argue that the key tenets of the established EP paradigm require modification in the light of recent findings from a number of disciplines, including human genetics, evolutionary biology, cognitive neuroscience, developmental psychology, and paleoecology. For instance, many human genes have been subject to recent selective sweeps; humans play an active, constructive role in co-directing their own development and evolution; and experimental evidence often favours a general process, rather than a modular account, of cognition. (Bolhuis et al., 2011)

The text parallels my recent paper in Futures, sometimes strikingly so. It starts off by observing that in the early years of evolutionary psychology “our knowledge of the human genome was limited and gradualism dominated evolutionary thinking.” Today, we know differently:

Events in the Holocene (the last 10,000 years), particularly the adoption of agriculture, domestication of animals, and the increases in human densities that these practices afforded, were a major source of selection on our species, and possibly accelerated human evolution. Evidence from the human genome strongly suggests that recent human evolution has been affected by responses to features of the environment that were constructed by humans, from culturally facilitated changes in diet, to aspects of modern living that inadvertently promoted the spread of diseases. (Bolhuis et al., 2011)

This recent evolution has especially shaped the human brain: “Genes expressed in the human brain are well-represented in this recent selection.”

Even when assessed on its own terms, the Pleistocene EEA looks more and more like a myth, and should be treated as such:

[…] the abstract concept of stable selection pressures in the EEA is challenged by recent evidence from paleoecology and paleoanthropology. The Pleistocene was apparently far from stable, not only being variable, but progressively changing in the pattern of variation. The world experienced by members of the genus Homo in the early Pleistocene was very different from that experienced in the late Pleistocene, and even early anatomical modern Homo sapiens that lived around 150,000 years ago led very different lives from Upper Paleolithic people (40,000 years ago) (Bolhuis et al., 2011)

Is a paradigm shift in the offing? Probably. But what form will it take? Perhaps the second question is unimportant. Whether evolutionary psychology changes or disappears, we’ll be looking at evolution and human behavior in a very different light.

To be cont’d


Bolhuis, J.J., G.R. Brown, R.C. Richardson, and K.N. Laland. (2011). Darwin in mind: New opportunities for evolutionary psychology, PLoS Biol 9(7): e1001109. doi:10.1371/journal.pbio.1001109

Frost, P. (2011). Human nature or human natures? Futures, 43, 740–748.

Tooby, J. and L. Cosmides. (2005). Conceptual foundations of evolutionary psychology, in: D. M. Buss (Ed.) The Handbook of Evolutionary Psychology, Hoboken, NJ: Wiley, pp. 5-67.

(Republished from Evo and Proud by permission of author or representative)
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  1. Rob says: • Website

    Recalls Haidt's speculation: "Such findings will be among the greatest threats to political correctness ever to emerge from the natural sciences."

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  2. I think that you overstate the case. There is absolutely no need for a paradigm shift; the objections you point out are all readily incorporated into the existing structure of evolutionary psychology. Consider, for example, the model of the EEA. Yes, it's simplistic to think in terms of the single EEA of a million years ago. It's more accurate to think in terms of an original EEA that changed slowly, and then suddenly blossomed into dozens of small EEAs once the species migrated out of Africa. Those small EEAs unquestionably exerted influence on local genomes, but they have not had much time to do so. Similarly, the dramatic shift to agriculture has created new selective pressures in the genome, which are manifesting themselves in a number of ways.

    Thus, the picture is one of a foundation built during the Pleistocene EEA, with modifications to that foundation developing later. What's the paradigm shift in that?

    Newton's Laws are almost never applicable in the real world, where things like friction interfere. But that doesn't mean that the inclusion of friction in calculations of motion constituted a paradigm shift, or that Newton's Laws are junk. They still provide the foundation for modern physics. (Yes, there WERE two subsequent paradigm shifts with relativity and quantum mechanics, but they both serve only to replace Newton's Laws in cases of high velocities or tiny sizes.)

    Undoubtedly it will be prudent to refrain from researching population differences; people are just not sophisticated enough to handle such results. Better to firmly establish the universal foundations first. That way, any population differences can be tied to rock-solid results already established. Any researcher who walks down that path will surely face mobs of torch-bearing, pitchfork-wielding rubes.

    In the same way, you go way too far when you declare that "These assumptions are false." They are first-round approximations. OF COURSE they don't fit the data ideally: they're approximations! Evolutionary psychology can still advance by simply tweaking those assumptions that you dismiss as flat wrong. For example, what if the three "flawed assumptions" were replaced as follows:

    1. The deepest foundations of human nature are uniform, but there are numerous alterations built on top of these foundations based on gender, culture, and history.

    2. The genetic basis of human nature was established over the course of the last million years, with an accelerating rate of change that is still slow by the standards of cultural evolution.

    3. All present-day humans share considerable behavioral traits, such as those documented in Human Universals, but most of the similarities exist only at the deepest underlying levels of behavior. Significant differences arise from local, cultural, and historical factors.

    I think that all three of these assumptions are well-founded, difficult to reject, and represent no paradigm shift. They are adjustments to the older, simpler assumptions that were appropriate in the early days of EP.

    Lastly, I implore you to refrain from using the pejorative term "just-so story". The Big Bang theory is a just-so story.

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  3. Tod says:

    Chris Crawford, The paridigm of Tooby does not allow that it is possible for any evolution of mental faculties to happen as quickly as it would need to have happened for northern climes (N. Europe was reached only 27,000 years ago) or agriculture to effect even minor changes.

    Tooby is saying that evolution stopped 35,000 years ago and that the the early Cromagnons were at least as intelligent as any people today. In fact I think it's pretty clear that Tooby's argument implies that stone age man was cleverer than people today as the kind of selection present in the EEA must have been relaxed with the coming of agriculture.

    "Pitchfork-wielding rubes' ? Hardly, the ones opposing a new paridigm are doing so because they know it's true, they've always known.

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  4. Well, Tod, it may be that Mr. Tooby is resisting adjustments, but he doesn't own EP; the theory is now the property of the community. Moreover, I'm dubious that Mr. Tooby is denying genetic change in the last 35,000 years when the lactose intolerance change has been so firmly demonstrated. C'mon, he can't be THAT stupid!

    And the "pitchfork-wielding rubes" comment was not directed at those who have scientific objections to EP; its target is the much larger group who ignorantly reject the entirety of EP as "just so stories".

    Lastly, I sense some confusion over the use of "paradigm" and "paradigm shift". It might be advantageous to re-read Kuhn on this. A clean simplification runs as follows: a hypothesis is a small speculation that addresses a single phenomenon; a theory is a larger speculation that addresses a class of phenomena; and a paradigm is an even larger speculation that addresses an abstraction covering a large range of phenomena.

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  5. Chris,

    I used to feel the way you do. Now, I feel otherwise. In a sense, we've become our own worst persecutors. We're controlling our thoughts and words in a way that would be impossible in a totalitarian state. This is the situation of self-censorship that now prevails in evolutionary psychology.

    You state: "I'm dubious that Mr. Tooby is denying genetic change [in mental traits] in the last 35,000 years when the lactose intolerance change has been so firmly demonstrated. C'mon, he can't be THAT stupid!"

    If one keeps repeating something that one knows to be false, one ends up half-believing it … all the more so if everyone else is doing the same thing. Strange, but true.

    I hope EP can change. And I'd be more than happy to call such change "tweaking," "adjustments," "minor modifications" — whatever. People need to save face, and I'm willing to play along.

    But please, let's stop saying that mental traits stopped evolving over a million years ago. It's just not true. It's not even close to being true.

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  6. Tod says:

    Lactose tolerance is not a mental faculty. As I understand it, Tooby is indeed denying evolution of mental faculties by genetic change in the last 35,000 years. That's his paradigm. If I remember rightly, Kuhn said that new ideas get accepted as the old scientists die off but Tooby's ideas seem to endure because those who openly dissent are culled.

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  7. Peter, I agree that self-censorship is almost as heinous as externally imposed censorship. I suppose that this is precisely why academic freedom is so important. But let us not forget the opprobrium visited upon Mr. Edward O. Wilson for his work in sociobiology. He wasn't that far off the mark, yet the rejection of his ideas — and himself personally — bordered on a witchhunt. The people who consider evolutionary psychology to be not just wrong, but evil, are legion. That's wrong, and I certainly don't permit it to silence me, but I can sympathize with anybody who decides to pursue something less controversial.

    If Mr. Tooby continues to deny the possibility of mental changes, then he's wrong, and that's that. But let me ask this: is he denying the possibility of genetically-based behavioral changes, or the existence of evidence for genetically-based behavioral changes? I am aware of a number of genetic changes over the last 35,000 years, but I can't recall a single one that manifests itself as a mental change. Can you refresh my memory, or is my memory for once reliable?

    I don't see the adjustments in EP as a matter of saving face. I don't see anything dramatically different about the perception of the phenomena described in this and the previous post. On the scale of scientific revolutions, this counts as little more than the local mayor being re-elected.

    I heartily agree that mental traits have changed enormously over the last million years, and I strongly suspect that there were some changes in linguistic processing as recently as 35K years ago. But since then, I can't recall any demonstrated changes in mental attributes. Again, please refresh my memory if I'm wrong.

    "Tooby's ideas seem to endure because those who openly dissent are culled."

    Wow, that would be ironic if Mr. Tooby is now perpetrating the same vindictiveness that was visited upon researchers like him 20 years ago.

    But again, we shouldn't identify EP with one person. Mr. Tooby and Ms. Cosmides deserve our respect for the way that they bravely broke down the barriers and got the ball rolling. Science progresses — if it has left them behind, that's sad, but our focus should be on the science, not the individuals.

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  8. Chris,

    I don't wish to downplay the witchhunt of the 1970s and 1980s, but we're now in the year 2011. Stephen J. Gould is dead and exposed as a charlatan. Richard Lewontin is a professor emeritus.

    If you're still afraid to say what you believe, then say nothing. Don't repeat falsehoods. And every morning, when you brush your teeth, remind yourself what a coward you are.

    "is he denying the possibility of genetically-based behavioral changes, or the existence of evidence for genetically-based behavioral changes?"

    The former, at least officially. His position is as follows.

    (a) Genetic determinants of behavior are too complex to have changed significantly over the past million years.

    (b) The human species has been in a virtual state of panmixia, i.e., there is much more variability within populations than between populations. Consequently, there can be no population-specific mental adaptations (and apparently no non-mental ones either).

    Does he believe the above two propositions? The answer is complex. He may have doubts, but those doubts have no easy channel for expression. People sometimes believe what is best for them to believe.

    "I am aware of a number of genetic changes over the last 35,000 years, but I can't recall a single one that manifests itself as a mental change. Can you refresh my memory, or is my memory for once reliable?"

    Genes expressed in the human brain are well represented in the genetic changes of the past 10,000 years. See:

    Hawks J, Wang E. T, Cochran G. M, Harpending H. C, Moyzis R. K (2007) Recent acceleration of human adaptive evolution. Proc Natl Acad Sci USA 104: 20753–20758

    Lloyd E. A, Feldman M. W (2002) Evolutionary psychology: a view from evolutionary biology. Psychological Inquiry 13: 150–156.

    Sterelny K (2003) Thought in a hostile world. Malden, MA: Blackwell.

    You might also wish to read up on the microcephaly gene variants, which are recent and have measureable impacts on brain size.

    Wang, J.K., Li, Y., and Su, B. (2008). A common SNP of MCPH1 is associated with cranial volume variation in Chinese population. Human Molecular Genetics, 17, 1329–1335.

    Rimol, L.M., I. Agartz, S. Djurovic, A.A. Brown, J.C. Roddey, A.K. Kähler, M. Mattingsdal, L. Athanasiu, A.H. Joyner, N.J. Schork, et al. for the Alzheimer’s Disease Neuroimaging Initiative (2010). Sex-dependent association of common variants of microcephaly genes with brain structure. Proceedings of the National Academy of Science. USA, 107, 384–388.

    There are also genetic determinants of reproductive strategy, personality factors, and the visual word form area. All of this is covered in my Futures article. I'll send you a pdf if you send your e-mail address to: pfrost61 at hotmail dot com

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  9. Anonymous • Disclaimer says:

    Polygyny and the Slave Trade.

    Of course, it could have been that polygyny was already well established in the West, and so those with more than one wife had an incentive to get rid of those at the bottom who might wish to usurp them.

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  10. Sorry for my delayed response. Peter, thank you so much for taking the time to dig up those papers for me! I am slowly going through them, learning much.

    I'm also saddened to learn that Mr. Tooby is taking so inflexible a position. As always, individual scientists can make brilliant contributions yet also be horribly wrong on some things. Einstein could never get quantum mechanics down his craw. Thanks for disabusing my naivete.

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  11. Tod says:

    Man's evolution: an introduction to physical anthropology, C Loring Brace, Ashley Montagu – 1965

    "In considering that there is a rough correlation between brain size and learning ability, it is obvious why cranial capacity increased during the greater part of the Pleistocene. Eventually a level was reached where the efficiency of the cultural adaptive mechanism was such that it benefited even those who were not able to completely master it. At such a point, individuals who could manage with the necessary minimum requirements of a culture could have just as good prospects for survival as those who could master their culture with ease…

    One might even speculate that if any differences in intelligence are discovered in the future they will be in inverse proportion to the efficiency of the cultural adaptive mechanism of the group concerned. In highly effective cultures even the dull witted can survive and reproduce, provided they can master at least the rudiments of their language and the mechanics of their social system."

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  12. Ishtara says: • Website

    Political correctness has become the new religion. All these little political correct half-truths and wild claims are very similar to a rigid religious dogma that uses moral outrage to shield itself from critical examination.

    My guess is that this PC craze will get worse before it gets better. Feminists have long been up in arms about the gender related findings in evolutionary psychology and other fields of science. Like different human populations, the two genders are supposed to possess equal skills and abilities.

    Woe unto those who suggest otherwise or cite the wrong study, they will share the fate of Lawrence Summers and Dr. Lazar Greenfield. All behavioral differences have to be attributed to cultural imprinting and human behavior can't possibly have a genetic basis. That's the religion of the 21st century. You may doubt that god exists, but don't you dare suggest that all humans are not created equal.

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  13. Anonymous • Disclaimer says:

    @ Mr. Crawford

    "Undoubtedly it will be prudent to refrain from researching population differences; people are just not sophisticated enough to handle such results. That way, any population differences can be tied to rock-solid results already established. Any researcher who walks down that path will surely face mobs of torch-bearing, pitchfork-wielding rubes."

    Who rules when people are sophisticated to listen to group differences? You? Sorry if I come off blunt but what entitles you to make that judgement? A scientist job isn't to withhold evidence or findings like the recent infamous late Gould did to promote his Marxist Utopia (ironic since it was he to pressed so hard over the idea that the culture makes scientist biased), but to rather publish unbiased work–as it is his duty to do so.

    I completely disagree with you and god help us if you are one in power who does withhold information.

    Must I remind you that point of origin doesn't prove sameness. Even if groups of humans have similar behavioral origins that makes a weak case that we are the same.

    @ Ishtara

    Here! Here! You took the words out of my mouth.

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  14. Anonymous • Disclaimer says: • Website

    Philosophers of art and politics have too often been like shyster lawyers creating clever diversions explaining odd and problematic outsider ideas rather than centering on the actual basis of human nature—although I suppose some lawyers actually believe their client is innocent. As Denis Dutton points out, the natural universal center of human nature is where theory needs to ground itself, cross culturally.

    The biggest lie is defining human nature as strictly a consequence of social institutions and as a cultural product, which now prevails throughout politics and the arts. This continues in the face of the latest science of sociobiology which shows that even the brain our genes built can be broken down into genetic modules which best suited our Pleistocene ancestors.

    The Pleistocene made us what we are today and only when we admit this knowledge into politics and the arts will we have healthier cultures. We simply are kin-centered, mostly ethnocentric, even xenophobic, with group-selection as the primary unit of selection, among many other traditional traits. These are universal traits in human nature that almost ironically point not to universal, egalitarian, borderless cultures, but suggest such politically incorrect things as ethnopluralism, economic nationalism, perhaps held together with federalism—and art which, at its best, affirms what each group holds sacred.

    It's overdo time to go there, even if the deniers continue to try to divert us with their hair-splitting.

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