Saturday, August 27, 2011

Was evolutionary psychology inevitable?

Cover of Time, August 28, 1995. Evolutionary psychology beat out its rivals in the race to win public acceptance.

During the 1990s, evolutionary psychology overtook and replaced sociobiology. Its success was total, much like that of many paradigms we now accept as normal science. Did it succeed for the same reason? Did it better fit the data?

In some ways evolutionary psychology was better than its rivals and in other ways worse. Its superiority tended to be more organizational, even political. In short, it became the only game in town for study of human behavior from an evolutionary perspective. The alternatives—sociobiology and gene-culture co-evolution—had much less to offer in terms of research funding, career opportunities, or just an untroubled academic life.

Early years of evolutionary psychology

At first, the term ‘evolutionary psychology’ simply referred to psychologists and psychiatrists who shared an interest in evolutionary theory. Such people began to come together in the late 1980s:

In mid-1987, an initial list of people using modern evolutionary theory to address problems in psychology and psychiatry was compiled and distributed. The respondents suggested additional names that expanded the list to over 200 researchers. Many people expressed surprise that there were so many others working in the area. Many more suggested that it was time to organize a forum for the exchange of ideas and research findings in the area. (Evolution, Psychology and Psychiatry 1988)

The first forum was held at the 1988 Evolution and Human Behavior Meeting in Ann Arbor, Michigan. The meeting had two purposes:

- To facilitate the exchange of ideas and findings among researchers in the area of Evolution, Psychology and Psychiatry. The developing new basic science will be emphasized.

- To consider plans for initiating an organization that will promote research and scholarly exchange in the area of Evolution, Psychology and Psychiatry.

The proceedings only hinted at evolutionary psychology’s eventual divorce from sociobiology. Some presenters talked about a mismatch between current behavior and earlier contexts of adaptation, but these contexts were not placed over a million years ago in the Pleistocene.

It was decided to have more meetings and to hold them annually. The 1989 meeting, now called the Human Behavior and Evolution Conference, had a similar mix of ideas. Presenters were now talking more about ‘mismatch’ and ‘mental mechanisms’:

Debate about the relevance of mental mechanisms, rather than current human behavior, to the study of adaptation continued from other conferences in the recent past. […] Turke pointed out that studies examining current reproductive success could reveal the nature of mental mechanisms by comparing contexts in which humans do or do not behave adaptively. […] The abstract models presented by evolutionary psychologists (first by Cosmides and Tooby), which are somewhat like descriptive structural equation models, seem often to be misunderstood to present physiological structures, again making mental mechanisms appear to promote invariant behavior. More sophisticated basic theory is necessary to determine whether current behavior reflects adapted strategies. (HBES, 1990)

Leda Cosmides and John Tooby were already arguing that the genetic determinants of human behavior had assumed their current form long before the emergence of Homo sapiens, but this view was still a minority one. Other presenters were affirming the possibility of much more recent evolution:

Cultural versus natural selection was also the major topic of a roundtable on the final morning, lead by William Hamilton, George Williams, Irenaus Eibl-Eibesfelt, Edward Wilson, Irven DeVore, and Richard Dawkins. Much of the discussion focused on the unit of selection and the selective process. Dawkins stressed defining a specific replicating unit, which must be genes or memes. Williams proposed using epidemiological, disease–transmission models for the spread of cultural traits rather than using genetic models. Wilson stressed the importance of co-evolutionary theory, which models the interaction of genes and culture in epigenetic processes. (HBES, 1990)

Evolutionary psychology was nonetheless en route to becoming a paradigm distinct from sociobiology, with the Pleistocene EEA as the key difference. In 1989, this theme inspired two articles in Ethology and Sociobiology. Don Symons wrote:

[…] a well-formed description of an adaptation must consist solely of words for things, events, relations, and so forth that existed in the EEA, which, in the case of human beings, means the Pleistocene world of nomadic foragers. The specific environmental features to which Tibetan polyandry is adapted, according to Crook and Crook, include agricultural estates, animal husbandry, primogeniture, monasticism, aristocrats, landlords, governments, and taxation. Because none of these things existed in the human EEA, Crook and Crook’s account contains not a single well formed description of a Darwinian adaptation […] (Symons, 1989, pp. 138-139)

John Tooby and Leda Cosmides argued along similar lines:

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. (Tooby & Cosmides, 1989, p. 34)

Here, Tooby and Cosmides assert that ‘whole new mental organs’ could not have arisen over the past million years. They then conclude that ‘major changes’ to mental organs are unlikely. This conclusion hardly follows from their initial assertion, which itself is doubtful. New organs have arisen over shorter time spans, specifically through duplication of an existing organ and rapid modification of the ‘spare.’

As a result of these articles and succeeding ones, the Pleistocene EEA came to define evolutionary psychology. The latter ceased to mean ‘sociobiology for psychologists’ and took on a narrower, more paradigmatic meaning.

Gene-culture co-evolution: a competing paradigm

At the turn of the 1990s, it was still far from clear that evolutionary psychology would take over from sociobiology. Gene-culture co-evolution seemed to hold a stronger position.

This other paradigm began in a cultural evolution class that L.L. Cavalli-Sforza taught in 1978-79 at Stanford to Robert Boyd and Peter Richerson (Stone & Lurquin 2005, p. 108). The Italian geneticist argued that the natural environment has not been the main driving force of human evolution. Instead, this role has largely fallen to the cultural environment, such as oral and written language, social organization, technology, means of subsistence, and so forth. There has thus been a feedback loop: we humans have created different cultural environments, which in turn have subjected us to different pressures of natural selection. Our creations have become our creators. This co-evolution fascinated Cavalli-Sforza, and its study now occupied his thoughts.

But others were thinking along the same lines, like the anthropologist Claude Lévi-Strauss in 1979:

[…] as anthropologists, the aspects of the question that will always appeal to us will be much less the genetic determination of culture or cultures than the cultural determination of genetics. […]

The selection pressure of culture—the fact that it favors certain types of individuals rather than others through its forms of organization, its ideas of morality, and its aesthetic values—can do infinitely more to alter a gene pool than the gene pool can do to shape a culture, all the more so because a culture’s rate of change can certainly be much faster than the phenomena of genetic drift.
(Lévi-Strauss, 1979, p. 24-25)

The 1980s saw growing interest from other students of human evolution. Robert Boyd and Peter Richerson were among the first, followed by Pierre van den Berghe, Charles Lumsden, E.O. Wilson, and R.D. Alexander. The new paradigm was summed up by Pierre van den Berghe:

[…] the causality between genes and culture is reciprocal […] culture, though clearly possessing some emergent and irreducible properties (notably in its mode of transmission), is itself subject to a wide set of developmental parameters because it comes out of a brain with a definite bio-chemical structure […] the human mind, despite its undoubted plasticity, is not a tabula rasa. It is predisposed to learn certain things with ease, and others with difficulty or not at all. According to this viewpoint, the programmed learning biases of the human brain result in a non-random distribution of cultural products […] Moreover, since culture has consequences for the survival and reproduction of flesh and blood organisms, natural selection must exert some influence on cultural evolution (van den Berghe & Frost, 1986)

Work on gene-culture co-evolution initially involved trawling through the ethnographic literature. In the mid-1980s, however, a major project for field research was launched, specifically among the Inuit of northern Canada.

Its leader? Cavalli-Sforza. The project was organized in 1986 with professors from Queen’s University and Université Laval. The aim was to determine whether natural selection favors different mental toolkits in hunting and gathering societies versus agricultural societies. As one project member, John Berry, a psychologist at Queen’s University, later explained:

Hunters, by this way of thinking, require good visual acuity, keen disembedding skills and a well-developed sense of spatial orientation. To hunt successfully, the hunter must be able to discern the object of the quest (which is often embedded in a complex visual landscape), then disembed the object, and finally return to home base. In contrast, agriculturalists need not develop these particular skills, but rather they need to invest in other areas of development, such as conservation (in both the economic and the Piagetian senses) and close social interactions. (Berry 2008, p. 3)

According to an unpublished report, Cavalli-Sforza wished to trace the origins of Inuit artistic talent by estimating the relative contributions of genetic endowment and socio-cultural learning:

One of the most remarkable phenomena in the contemporary Canadian Arctic is the presence of highly-acclaimed art forms — carving in stone and ivory, and printing on paper. The question we ask is: how can we account for the wide-spread distribution of such talent in a small dispersed population?

[…] Is it possible that artistic talent is transmitted culturally (from parents to offspring, from others in society to the artist, and from peers to artist)? How can we assess these types of transmission?

Is it possible that artistic talent is transmitted genetically (from parents to offspring)? How can we assess such transmission?
(Berry & Cavalli-Sforza 1986, p. 2)

The approach would be to study specific Inuit artists and then their biological and non-biological relatives. The high rate of adoption among Inuit (between 15 and 30%) would provide a means to distinguish cultural inheritance from genetic inheritance in the transmission of artistic talent. Related mental traits would also be investigated. “Given enough information one can hope to separately estimate two quantities, called respectively cultural and genetic heritability” (Berry & Cavalli-Sforza 1986, p. 5)

The project fell through. At Laval, we assumed something went wrong with the funding. At Queen’s, the story was that Cavalli-Sforza had quit because of illness. Yet his biography makes no mention of illness during this period, the only bouts of ill health being an operation for bladder cancer in 1976 and a heart attack in 1991 (Stone & Lurquin, 2005, pp. 98, 160). In any case, ill health would have been a reason for postponing the project, not canceling it.

This project has left no traces in any of Cavalli-Sforza’s publications—books, journal articles, conference proceedings, or poster sessions. The paper trail amounts to one unpublished report (Berry & Cavalli-Sforza, 1986). Just as mute are his published writings on gene-culture co-evolution. Examples are confined to the usual suspects: lactose tolerance in cattle-raising societies, and malaria resistance among tropical agriculturalists (Cavalli-Sforza & Cavalli-Sforza 2008, p. 264). There is no hint that natural selection might have favored different mental traits in different cultural environments.


With Cavalli-Sforza gone, the field of gene-culture co-evolution lost momentum. It had big names, but few of them could put boots on the ground, i.e., do fieldwork. Nor could any of them focus on this area of research. As big names, they typically had their fingers in many pies.

There may have been another reason in the case of Cavalli-Sforza. He was vulnerable to blackmail because of his wartime anthrax research … in Berlin. Nothing terrible came of that laboratory work, but it had the potential to derail his career. At the very least, it was a stain on his curriculum vitae. (1)

Evolutionary psychology thus beat out its rivals by default. The term ‘sociobiology’ was becoming a mark of Cain even among people interested in human behavior and evolution. In 1997, it was literally voted out of existence. Gene-culture co-evolution continued to attract interest but only as a sideline.

With its rivals growing ever weaker, evolutionary psychology gained strength as the millennium drew nearer. It could now offer grad students a hassle-free research environment with a real chance of academic employment later on. This may have been due to avoidance of the stormy issue of population differences (although academia in general was becoming calmer). A bigger reason, however, was the strong focus of its main proponents, John Tooby and Leda Cosmides. They talked at conferences, gave interviews to the media, networked, and published, published, published. As they slowly climbed the academic career ladder, they would turn around to help likeminded people on lower rungs.

Bit by bit, they did what the big names could not do. They created a new teaching and research environment. And this environment would be called ‘evolutionary psychology.’


1. Whenever Cavalli-Sforza lists his publications he never goes farther back than 1947. His wartime publications are all the more unknown because they were published under the name of Cavalli. He later changed his name to Cavalli-Sforza, having been ostensibly adopted by the second husband of his maternal grandmother. His autobiography dates the name change to 1950 (a year after his father died) when he was 28, married, and already a father. Such circumstances hardly justified adoption under Italian law or custom. Even more inexplicably, he was still publishing under his old name as late as 1953. Google Scholar lists three publications by L.L. Cavalli in 1950, one in 1951, five in 1952, and two in 1953.


Berry, J.W., and L.L. Cavalli-Sforza. (1986). Cultural and genetic influences on Inuit art. Report to Social Sciences and Humanities Research Council of Canada, Ottawa.

Boyd, R. and P.J. Richerson. (1985). Culture and the Evolutionary Process, Chicago: Chicago University Press.

Cavalli-Sforza, L.L. and F. Cavalli-Sforza (2008). La génétique des populations : histoire d'une découverte, Paris: Odile Jacob. (French translation of Perché la scienza : L’aventura di un ricercatore).

Evolution, Psychology and Psychiatry. (1988). Meeting Announcement, Ann Arbor, Michigan, October 28-30, 1988.

HBES. (1990). Summary of the first Human Behavior and Evolution Conference: Evanston, Illinois, August, 1989, Human Behavior and Evolution Society Newsletter, 1(1), 2-4, July 1990.

Lévi-Strauss, C. (1985). Claude Lévi-Strauss à l’université Laval, Québec (septembre 1979), prepared by Yvan Simonis, Documents de recherche no. 4, Laboratoire de recherches anthropologiques, Département d’anthropologie, Faculté des Sciences sociales, Université Laval.

Stone, L. and P.F. Lurquin. (2005). A Genetic and Cultural Odyssey. The Life and Work of L. Luca Cavalli-Sforza. New York: Columbia University Press.

Symons, D. (1989). A critique of Darwinian anthropology, Ethology and Sociobiology, 10, 131-144.

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

van den Berghe, P. L. & P. Frost. (1986). Skin color preference, sexual dimorphism, and sexual selection: A case of gene-culture co-evolution? Ethnic and Racial Studies, 9, 87-113.


Harmonious Jim said...

Maybe evolutionary psychology became more sexy because it studied sex, always a hot topic with the media, whereas the other rival evolutionists were looking at duller subjects?

Kiwiguy said...

Have you or anyone else asked Cavalli-Sforza about the Inuit project?

Anonymous said...

Bruce Lahn: The fact that humans are capable of advanced culture and other species are not must be genetically based. Humans are cultural not just because of the environment, but rather because humans have acquired a set of genetic changes that other species didn’t have the great fortune to acquire. Cultural evolution definitely has a genetic basis. Nobody would deny that.

Chris Crawford said...

A fascinating tale; thanks so much for taking all that effort to get those details together. My gut hunch is that, at some point in the future, scholars will look back on those decades with the same awe that physicists feel when they consider the quantum revolution of the late 20s through the 30s.

Two questions:

First, I was under the impression that the concept of "gene-culture coevolution" was something a political ploy to counter the angry criticisms early directed at what was termed "genetic determinism". Am I wrong here?

Second, on the matter of Cosmides and Tooby insisting that no new organs developed since the Pleistocene: it seems to me that everything hinges on the definition of "organ". Basic mammalian anatomy (eyes, ears, kidneys, lungs, livers, etc) has not changed for a very long time, possibly not since Triassic times. Hence, it is possible to treat "organ" as something that has most certainly not changed in a mere million years.

How finely do we cut up the human mind? Sure, we can readily differentiate some functions, such as the visual cortex, because they are strongly localized -- but the visual cortex has had its basic layout since the first full primates. We can divvy up aural processing less cleanly, and when it comes to linguistic processing, there are some clear localizations, (Broca's area, Wernicke's area) but there are also some functions distributed over a lot of neural territory.

I'd like to again thank Peter Frost for his list of papers discussing recent changes in human mental function. One thing that struck me about these papers is that (so far, at least), the changes in mentation that we have seen in the last 35,000 years seem to be fairly low down in the architecture of the mind -- that is, not representing fundamental shifts. This is, of course, obvious -- but again, where do we draw a line between "big changes" and "little changes"?

We should surely expect some major changes in mentation to arise from the huge step from the hunter-gatherer lifestyle to the agricultural lifestyle; Cavalli-Sforza's proposed research program seemed like a perfect way to address this -- has anybody ever completed such a project? Is there any overall compilation of differences in mentation between hunter-gatherers and agricultural peoples?

OK, I lied -- six questions, maybe seven...

Peter Frost said...

Harmonious Jim,

Evolutionary psychologists have been better at PR. This might have something to do with the field of psychology itself, which seems to have a higher profile in the media and popular culture. Academics in other fields tend to be wary of non-academics.


Yes. He told the folks at Queen's University that he had to quit because of poor health, and that was it. Even with research associates, Cavalli-Sforza tends to be circumspect.


In other words, the ability to learn is not a learned ability.


Yes, gene-culture co-evolution was spun that way. "We're not just interested in how genes determine culture. We're also interested in how culture determines genes."

That "spin" was surprisingly successful. When you think about it, both ideas are equally controversial.

"Organ", like "mental mechanism", is just a word. A better term might be "mental algorithm."

Would you call the human voice box an organ? Wasn't that a big change?

In my opinion, the biggest change in recent human evolution was the shift to symbolic thinking and the ability not only to imagine objects in all three dimensions (and the dimension of time) but also to manipulate this mental simulation, i.e., examine the outcomes of different hypothetical scenarios.

Anonymous said...

"The Italian geneticist argued that the natural environment has not been the main driving force of human evolution."

If a population group are in a particular ecological niche it seems plausible their culture would evolve to adapt to it and that culture will then start to exert selective pressure on individuals.

If the group moves into a different ecological niche then the process will start over again.

As humans are social animals culture could be seen as the group adaptation to the environment which then creates selection pressure for individual level adaptations.

The EP vs sociobiology thing sounds like a battle in the ongoing hundred years war to prevent science getting to the truth in case the conclusions are politically incorrect.