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.

Endgame

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.’

Note

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.

References

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.

Can evolutionary psychology evolve?

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

References

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
http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001109

Frost, P. (2011). Human nature or human natures? Futures, 43, 740–748.
http://dx.doi.org/10.1016/j.futures.2011.05.017

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.

Evolution and human behavior: Towards a new paradigm?

Illustration from Darwin’s book The Expression of the Emotions in Man and Animals (1872)

Evolution has shaped not only our anatomy but also our behavior. This was recognized by Charles Darwin himself in his work The Expression of the Emotions in Man and Animals (1872). Not until the early 20th century, however, would evolution and human behavior emerge as a real field of study. It has gone by three successive names so far:

Ethology

This largely German school began in 1937 with the founding of the journal Zeitschrift für Tierpsychologie, mainly through the efforts of Konrad Lorenz. The initial aim was to understand the evolutionary origins of human behavior by identifying human behavioral patterns, by examining how they develop during the life of an individual, and by comparing them to homologous behaviors in other primates and mammals.

From the 1960s onward, ethology increasingly shunned the study of human behavior, ostensibly because only nonhuman species could be observed under controlled conditions. Once we had fully understood how and why they behave, it would then be possible to move on to humans. This self-imposed limitation became self-reinforcing: only zoologists went into this field of study, and the occasional musings about human behavior tended to be amateurish.

When did ethology cease to mobilize research into human behavior? The cut-off date probably lies shortly after Lorenz’s death in 1989 and the publication of Human Ethology by his student Eibl-Eibesfeldt the same year.

Sociobiology

Launched in the late 1970s, this North American school drew heavily on the latest developments in evolutionary thinking, which in turn drew on economics and game theory. From the outset, it ran into a firestorm of opposition that doomed any real chances for growth or even survival.

Even under better circumstances, it is doubtful whether this field of study could have survived without serious rethinking. Its main shortcomings were:

- “presentism,” a tendency to see contemporary human behavior as an adaptation to present environments, however recent or novel they might be.

- a resulting tendency to see modern behavior as being necessarily adaptive, despite evidence to the contrary. Falling birth rates, for instance, were attributed to parents switching to a K-type reproductive strategy.

- a disinterest in the actual pathways by which genes influence behavior. Such influences were said to be unknowable. Instead, sociobiologists preferred to invoke a mysterious “fitness-maximizing mechanism.”

- naïve and often impressionistic use of anthropological data

By the 1990s, few sociobiologists wished to identify themselves as such, if only because the term itself had become an obstacle to public acceptance. In 1997, this field did away with itself. Its leading journal, Ethology and Sociobiology, was renamed Evolution and Human Behavior.

Evolutionary psychology

This school is likewise North American and largely based in California, its leading pioneers being Leda Cosmides, John Tooby, Don Symons, and David Buss. It took over from sociobiology in the mid-1990s and still dominates thinking on the evolutionary origins of human behavior. Its writers come overwhelmingly from psychology and to a lesser extent from anthropology, biology, and even the humanities. Psychologists are over-represented largely because their discipline better weathered the anti-sociobiology firestorm of the 1980s.

In reaction to sociobiology, evolutionary psychology sought to understand the actual ways in which genes influence behavior, which was now seen as an adaptation to past environments. This school developed around four basic principles:

1. The environment of evolutionary adaptedness (EEA). Past environments have shaped human nature. How far back in the past is not clearly stated, although the EEA has typically been equated with the savanna of Pleistocene Africa.

2. Gradualism. The human mind is a product of co-adapted gene complexes that cannot respond quickly to selection. Like the EEA, gradualism denies that human nature could have evolved differently in the different cultural and physical environments that modern humans entered as they spread out of Africa over the past 40,000 years

3. Modularity of the human mind. Because specific adaptive problems require specific adaptive solution, the human mind is mainly composed of domain-specific, modular programs.

4. Universal human nature. There is only one human nature. Apparent differences in human nature are simply different outcomes of species-wide programs (as a result of different environmental inputs).


The above principles are more than a reaction against sociobiology. They’re an overreaction. Some genetic determinants of human behavior are clearly post-Pleistocene in origin. How are we supposed to explain them? And what about more domain-general aspects of the human mind, like general intelligence?

But, then, this “overreaction” isn’t just a matter of rational argument. There is also fear. Leda Cosmides and John Tooby remember the firestorm that ravaged sociobiology in the 1980s. They then wandered a long time in the wilderness before finally landing a permanent academic position. Time and again, they had to convince potential employers or funding agencies that they had no secret interest in psychological differences among human populations.

And so was paved the road to evolutionary psychology, a road paved with the best of intentions: legitimate criticisms of sociobiology, with an understandable desire to lead a normal academic life.

This desire is described by Cosmides and Tooby in one of their articles:

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. (Barkow, Cosmides, & Tooby, 1992)

Ironically, in seeking to challenge this modus vivendi, Cosmides and Tooby have ended up creating a new one. We can now study human behavior from an evolutionary perspective, but only if we exclude (1) psychological differences between human populations and (2) domain-general aspects of human behavior, e.g., general intelligence. That’s the implicit deal behind evolutionary psychology—an acquiescence to self-censorship.

How has the deal worked out? Quite well, apparently. Evolutionary psychology has attained a degree of respectability that seemed impossible back in the mid-1990s. In 1995, only 261 newly published academic books or articles mentioned the term “evolutionary psychology.” Last year, the figure was 3,570 (see Google Scholar). This field now has its own handsomely illustrated textbooks, grad school programs, and research centers. Perhaps more importantly, it now incurs few costs to a career in academia.

But maybe this would have happened anyway. By the mid-1990s, the anti-sociobiology firestorm was burning itself out. The far left had entered a steep decline, and its graying leadership was pushing sixty. With rising tuition, a weakening economy, and aging demographics, the social sciences were attracting fewer and better students. Meanwhile, the advent of the Internet was “deregulating” the marketplace of ideas.

Has self-censorship calmed debate over evolution and human behavior? I’m not so sure. In any case, it has certainly done much to distort the way the debate is framed. And this is the sad part. Evolutionary psychologists often produce interesting findings, only to fall down when they try to interpret them.

For instance, it is known that children develop differently if the biological father is absent and a strange male is present (e.g., a stepfather). In both sexes, sexual activity will begin earlier with less stable pair bonds. Sons will show hypermasculine behavior, such as aggressive acting out, boasting, and risk-taking. Daughters will reach puberty earlier and judge potential mates by current appearance and status in the male hierarchy rather than by steadfastness and ability to support a family. It has thus been hypothesized that an early sensitive period allows certain environmental cues, like father presence, to define reproductive strategy later in life (Ellis et al., 2003).

The above reasoning is consistent with the four principles of evolutionary psychology. It’s also false. A recent twin study has found that early menarche is predicted as strongly by a step-uncle’s presence as by a stepfather’s. “It does not seem necessary for a child to experience the direct environmental influence of a stepfather to exhibit an accelerated age of menarche—as long as she is genetically related to someone who does have a stepfather” (Mendle et al., 2006).

In other words, a woman may be more prone than others to early menarche, a high degree of female reproductive autonomy, and low expectations of paternal investment. It’s not as if she acquires this reproductive strategy from her childhood environment. Instead, she inherits it genetically from her mother and absent father.

So where do we go from here? We can continue down the road paved by Cosmides and Tooby. But it will often take us to a dead end. We’ll then have to waive some or all of the above four principles, assuming of course we wish to understand human behavior.

To be cont’d

References

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.

Ellis, B.J., J.E. Bates, K.A. Dodge, D.M. Fergusson, L.J. Horwood, G.S. Pettit, L. Woodward. (2003). Does father absence place daughters at special risk for early sexual activity and teenage pregnancy? Child Development, 74, 801-821.

Mendle, J., E. Turkheimer, B.M. D’Onofrio, S.K. Lynch, R.E. Emery, W.S. Slutske, and N.G. Martin. (2006). Family structure and age at menarche: a children-of-twins approach, Developmental Psychology, 42, 533-542.

Brain size, latitude, and ambient light

An Inuk wearing snow goggles. Is ambient light at its lowest in Inuit territory?

The logjam seems to have broken. On the heels of Lewis et al. (2011), we now have another paper on variation in brain size among human populations, this time by Pearce and Dunbar (2011).

Brains vary in size by latitude, being bigger at higher latitudes and smaller at lower ones. This variation seems to reflect an adaptation to climate. But just how, exactly, does climate relate to brain size? How direct or indirect is the relationship?

Pearce and Dunbar (2011) argue that bigger brains are an adaptation to lower levels of ambient light. Specifically, dimmer light requires larger eyes, which in turn require larger visual cortices in the brain. Using 73 adult crania from populations located at different latitudes, the two authors found that both eyeball size and brain size correlate positively with latitude. The correlation was stronger with eyeball size, an indication that this factor was driving the increase in brain size.

How credible is this explanation? First of all, visual cortex size was not directly measured. The authors inferred that this brain area was responsible for the increase in total cranial capacity. Obviously, they couldn’t have done otherwise. They were measuring skulls, not intact brains.

But there’s another problem—one in the realm of logic. A lot of things correlate with latitude: pigmentation, mating systems, rules of descent, degree of paternal investment, and so on. If one of them correlates more strongly with latitude than the others, does it therefore cause the others? Not at all. It may be closer than the others to this shared cause, but it doesn’t necessarily lie on the same causal chain as the others.

In other words, the level of ambient light does not produce a single cascade of consequences, with eyeball size being the first consequence. There are probably many different cascades.

To date, the best map of human variation in brain size is the one by Beals et al. (1984) (see previous post). If dimness of light is the main determinant, brain size should be highest in northwestern Europe, northern British Columbia, the Alaskan panhandle, and western Greenland. These regions combine high latitudes with generally overcast skies. Yet they are not the regions where humans have the biggest brains. Instead, brain size is at its highest among humans from the northern fringe of Arctic Asia and from northeastern Arctic Canada. These regions are, if anything, less overcast than average. They often have high levels of ambient light because of reflection from snow and ice.

The jury is still out on this question. I suspect, however, that the following three factors probably explain variation in brain size with latitude.

1. Among hunter-gatherers, hunting distance increases with latitude because there are fewer game animals per square kilometer (Hoffecker, 2002, pp. 8-9). Hunters must therefore store larger amounts of spatiotemporal information (landmarks, previous hunting itineraries, mental simulations of possible movements by game animals over space and time). This factor might explain why brains have grown smaller since the advent of agriculture.

2. The seasonal cycle matters more at higher latitudes. As a result, northern hunter-gatherers, and northern agriculturalists even more so, must plan ahead for the next season (or even for the season after the next one).

3. Women gather less food at higher latitudes and almost none in the Arctic. They are thus free to specialize in other tasks, such as garment making, food processing, and shelter building. This “family workshop” creates opportunities for greater technological complexity, which in turn increases selection for greater cognitive performance.

I suspect bigger brains provide not so much greater intelligence as greater ability to store information. As such, they nonetheless pre-adapted northern hunter-gatherers for later advances in cultural evolution.

References

Beals, K.L., C.L. Smith, and S.M. Dodd (1984). Brain size, cranial morphology, climate, and time machines, Current Anthropology, 25, 301–330.

Hoffecker, J.F. (2002). Desolate Landscapes. Ice-Age Settlement in Eastern Europe. New Brunswick: Rutgers University Press.

Lewis, J.E., D. DeGusta, M.R. Meyer, J.M. Monge, A.E. Mann, R.L. Holloway. (2011). The Mismeasure of Science: Stephen Jay Gould versus Samuel George Morton on Skulls and Bias, PLoS Biology, 9(6) e1001071

Pearce, E. and R. Dunbar. (2011). Latitudinal variation in light levels drives human visual system size, Biology Letters, doi: 10.1098/rsbl.2011.0570

Rapid cultural evolution: the case of the Iroquois

Cahokia, an Amerindian town on the Mississippi of 10,000 to 20,000 people. A forerunner of what might have been?

Native Indian societies are widely seen as unchanging before Europeans came into the picture. This view sometimes has almost religious overtones. Amerindians lived in harmony with their world, and this harmony was broken by the White man.

Yet this view is at odds with a growing consensus among archeologists. Rapid cultural evolution was already under way in eastern and central North America when the first Europeans arrived. Had their arrival been postponed long enough, they would have encountered millions of sedentary Indians in a zone stretching from the lower Mississippi to southern Ontario. A northern Aztec Empire.

The northern end of this zone experienced the most rapid change. Nomadic hunter-gatherers roamed over southern Ontario and New York State until late in prehistory. Then, some time after 500 AD, these Iroquoian-speaking peoples began to settle into villages and cultivate corn, beans, and squash.

After a slow start, this cultural evolution began to accelerate circa 1300 AD. The result, according to anthropologist Bruce Trigger, was “a dramatic revolution in Iroquoian life”:

[…] Houses became longer and were inhabited by many more families. The length of the houses varied greatly. They were located closer together and began to be aligned parallel to one another in groups that may have been occupied by related matrilineages or individual clans. Villages were surrounded by more elaborate fortifications, and at least some of the village planning may have been intended to reduce the amount of palisades that had to be constructed and manned in order to defend a settlement (Noble 1969:19). Higher frequencies of house extensions and of interior house post densities suggest that individual houses were being occupied for longer periods than previously. This would also have encouraged sturdier construction. (Trigger, 1985, p. 92)

These changes in material culture went hand in hand with an increase in social complexity:

In New York State cultural groupings ancestral to the historical tribes of that region - including the Five Nations Iroquois - also become more clearly defined. […] In all these areas many communities continued to increase in size, probably mainly as a result of the union of two or more existing ones. Many settlements had 1,500 inhabitants. While houses became shorter, they still differed considerably in size. Village planning became more elaborate, with open spaces being provided as work areas and for the disposal of garbage. (Trigger, 1985, p.100)

The increase in social complexity brought changes in political organization:

[…] There is also widespread evidence at this time of neighbouring and hitherto autonomous settlements clustering close to one another to form "tribes." The best documented example is Tuck's (1971:214-16) demonstration that two villages, one small and the other much larger, settled within a few kilometres of each other between AD 1450 and 1475 to found the Onondaga nation. The larger village was itself the result of an earlier fusion of two small ones. This drawing together of communities to form larger settlements and tribes led to the abandonment of many formerly settled areas and produced more widely separated clusters of human habitation. It also created new political groupings, each of which embraced more people than any previous ones in this part of North America had. (Trigger, 1985, p. 102)

There were also ideological innovations that may have come from places farther south, such as the ritual killing of prisoners of war:

Certain key elements, including the use of prisoners, the removal of the heart, the killing of the victim on an elevated platform and in view of the sun, and finally the cooking and eating of all or parts of his body, connect this northern Iroquoian ritual with ones practised in the southeastern United States and in Mexico by the Aztecs, although many specific differences remain. (Trigger, 1985, p. 97)

Finally, there was an intensification of warfare that began before the arrival of European traders or settlers:

There is now also much archaeological evidence of warfare after AD 1400 between Iroquoian groups in the London area and the Fort Meigs culture, found in extreme southwestern Ontario and around the western end of Lake Erie. […] Hence the warfare between the Neutrals and the Central Algonkians which continued into the 1640s might have been the final stages of a conflict that had begun in the prehistoric period. (Trigger, 1985, p. 107)

Trigger concludes that these processes of State formation and militarization were endogenous:

[…] archaeologists may have oversimplified the late prehistory of the Iroquoian peoples and underestimated the dynamism of their cultural pattern and its capacity to generate new forms of creative and destructive behaviour. The Iroquoians now seem to have evolved the essential features of their way of life before the first Europeans appeared along the east coast of Canada. (Trigger, 1985, p. 108)

This cultural evolution was actually accelerating when the Europeans arrived. What if their arrival had been postponed? The Iroquois would have certainly surpassed the mound builders of the Mississippi valley and probably reached a level of civilization like that of the Aztecs.

Such a scenario almost did happen. Indeed, conditions were far from ideal when the English and the French began to settle North America. Western Europe was just returning to the population levels that had existed before the Black Death. The North Atlantic was entering a cold period, called “The Little Ice Age,” that made trans-oceanic crossings difficult. Finally, the Turks were pushing deep into Central Europe, laying siege to Vienna in 1529 and 1683 and vowing to drive on to Cologne.

Had this fragile context taken a turn for the worse, there might have been insufficient will or ability to colonize the Americas. European settlers would have perhaps arrived on the Eastern Seaboard only in the late 1700s.

And beyond the Appalachians, they would have found millions of sedentary Amerindians living in fortified cities and recently united under the aegis of the Iroquois Confederacy …

Reference

Trigger, B.G. (1986). Natives and Newcomers: Canada's "Heroic Age" Reconsidered, Montreal: McGill-Queen's University Press.

Continent orientation, cultural evolution, and the Amerindian exception

Pre-Columbian copper artifacts from Illinois, Oklahoma, Missouri, and Illinois.

In my last post, I criticized Jared Diamond’s theory about continent orientation and cultural evolution. This theory posits that people, and hence ideas, are likelier to circulate along an east-west axis than along a north-south one. This is because people tend to move about in environments that have similar climates and ecosystems. Eurasia has thus reaped the benefits of having a belt of societies—stretching from Spain to Japan—that can borrow new ideas from each other with relative ease.

This is not the case with sub-Saharan Africa, which is oriented north-south. It has a much more limited pool of ideas to draw upon. Diamond argues that this is one big reason why sub-Saharan Africans failed to develop beyond the stage of simple agricultural societies.

But what about the Americas? Aren’t they even more north-south oriented? How, then, did advanced civilizations develop in Mesoamerica and the Andes? And why did they develop even faster than ancient civilizations in Eurasia?

These were the questions I raised in my last post. Here, I’ll argue that this fast pace of cultural evolution was not limited to Mesoamerica and the Andes.

Take the transition from hunting and gathering to agriculture. Around 100 BC, agriculture was still confined to the American southwest. The rest of the present-day United States was home to nomadic hunter-gatherers. By 800 AD, agriculture had spread throughout most of the central and eastern U.S. and into southern Ontario. By 1000, the Mississippi valley had urban centers that were each built around a central plaza with earthen temple mounds. These developments were accompanied by a suite of cultural innovations: skilled metalworking; food storage in pits and cribs; timber palisades and bastions; and formation of intertribal confederacies.

This pace of change was, if anything, faster than comparable change elsewhere in the world. There is little evidence that the availability of new ideas was a significant brake on cultural evolution in the Americas—at least no more so than in Eurasia, where new ideas were supposedly more available. Agriculture, for instance, took more than five thousand years to spread from the Middle East to northern Europe.

Indeed, there is evidence of ancestral Amerindians having access to useful ideas that they nonetheless chose not to use. The wheel, for instance, was known to the Aztecs, who used it for toys. But they never used it for anything else.

Another example is copper working. This metal had been worked in eastern North America since at least 5,000 BC, and the resulting artifacts were “far larger and better shaped than any known native copper objects from the Middle East” (Smith, 1968, p. 242). Yet there was never any melting, smelting, casting, or alloying of copper. In particular, there was no attempt to harden copper by combining it with tin, lead, antimony, or arsenic, although such elements were available in the Americas. Such possibilities were there for the taking, but there was apparently little interest in doing so.

As Ehrhardt (2009) comments, “It is provocative and useful to think about why North American metal working technology did not follow the same developmental paths documented for other New World metal working industries.”

One factor may have been the overwhelming use of copper for status or ritual purposes, i.e., ornamentation that did not require hard metals (Ehrhardt, 2009). While such purposes certainly prevailed in Old World civilizations, the latter also used metalworking to make functional objects like kitchenware and tableware. Perhaps New World civilizations suffered not from a lack of ideas but rather from limits on the use of ideas. Mental innovation was subordinated to the interests of the ruling caste. The needs of ordinary folk came a distant second.

Thus, the availability of new ideas is not the main brake on cultural evolution. What matters more is the perceived usefulness of those ideas, and the people who decide which ones are useful and which are not.

Further thoughts

Why did cultural evolution follow a more fruitful path in the Americas than in sub-Saharan Africa? The latter had more opportunities for east-west exchange, being next to Eurasia and its cultural innovations. According to Diamond’s theory, cultural evolution should have been faster in sub-Saharan Africa than in the Americas. Yet the reverse happened.

How come? The main reason was that Amerindian men and women had to plan over a predictable yearly cycle. The men also had to provide for their mates and children, especially in winter—an obligation that not only integrated father, mother, and children into a single unit of family production but also freed the mother to specialize in other tasks, like garment making, food processing, and home building.

These factors pre-adapted Amerindians for later cultural evolution. The “family workshop” of nomadic hunter-gatherers became a model for the economic and political structures of sedentary farmers.

References

Diamond, J. (1997). Guns, Germs and Steel: The Fates of Human Societies, New York: W.W. Norton.

Ehrhardt, K.L. (2009). Copper Working Technologies, Contexts of Use, and Social Complexity in the Eastern Woodlands of Native North America, Journal of World Prehistory, 22, 213-235.

Smith, C. S. (1968). Metallographic study of early artifacts made from native copper (pp. 237–252). Warsaw: Actes du XIe Congrès International d’Histoire des Sciences VI.

Big Other?

Julos Beaucarne, March 2007

Your Christ is Jewish
Your car is Japanese
Your couscous is Algerian
Your democracy is Greek
Your coffee is Brazilian
Your chianti is Italian

And you reproach your neighbor for being a foreigner

The above poem, by Belgian singer Julos Beaucarne, has been making the rounds of late-night radio and Facebook pages for the past few years. Its message? Without the contributions of other cultures, we’d be less advanced, less refined, and less well off. In short, we’d be nobodies. We have met the Others, and they are us.

This is Big Other at its finest. If poetry leaves you cold, a more intellectual version is available in the pages of Guns, Germs and Steel: The Fates of Human Societies by Jared Diamond.

Diamond starts off by noting that people, and hence ideas, are more likely to circulate between regions that are ecologically and climatically similar. Hence, the circulation of ideas tends to be much more east-west than north-south.

If we look at a world map, we see that Eurasia is oriented east-west and Africa north-south. Eurasians have thus benefited from a greater number of cultural innovations because they can tap into a belt of human creativity stretching from Gibraltar to Tokyo. Africans, by contrast, have not had this advantage. This, argues Diamond, is one big reason why Africa fell behind Eurasia in the race for global dominance.

Absent from this argument is any mention of the Americas. Those continents likewise follow a north-south axis, even more so than Africa. Yet they became home to advanced civilizations in Mesoamerica and the Andes. There is some evidence that the Incas had cultural contacts with Polynesian seafarers. Other than that, both of these civilizations had to develop on their own.

Did they develop more slowly than Eurasian civilizations? Apparently not. Mesoamerican civilizations reached milestones in cultural development at a faster rate than did civilizations in the Middle East. The Zapotecs developed calendar and writing systems barely 1,000 years after their first permanent farming villages. In the Middle East, the time span was over 5,000 years.

Jared Diamond, like Julos Beaucarne, is begging the question. Yes, as Eurasian cultures came more into contact with each other, they each had fewer innovations of local origin and more of foreign origin. But would these cultures have been worse off if forced to innovate on their own?

Indeed, an argument can be made that exposure to the “Other” tends to stifle local creativity. During the thirty years after the Second World War, Americans lived under a regime of semi-autarky, producing most of their own goods, educating most of their own talent, and generating most of their own inventions. This was nonetheless a period of almost frenetic cultural and economic innovation. Is the United States more innovative today, now that it’s much more open to the rest of the world?

It is even doubtful whether the east-west flow of ideas explains the rise of the European world to global dominance between 1500 and 1900—the main theme of Diamond’s book. This rise to dominance was fueled by a technological revolution that occurred largely in northwestern Europe, with the exception of only two major innovations of non-European origin: gunpowder and the printing press.

Before 1500, Europeans did borrow considerably from the Middle East in such fields as chemistry, mathematics, and engineering, but this was a time of slow economic growth and geopolitical weakness. Europe took off economically and geopolitically only when it developed its own intellectual resources.

Reference

Diamond, J. (1997). Guns, Germs and Steel: The Fates of Human Societies, New York: W.W. Norton.