Confronting the elephant in the human biodiversity room — the explosive issue of IQ

Credit: ClearVoice
Credit: ClearVoice

Here’s a thought experiment. Imagine two widely separated human groups living for thousands of years in different cultural and ecological environments. One population faces constant cognitively demanding challenges, such as a never-ending need to meet and overcome natural and human threats. The other group is largely buffered from such environmental dangers, with the biggest trial simply to survive endemic disease. In which population would there be more selective pressure for greater intelligence? 

This is reasoning used by biogeographer Jared Diamond to argue why “modern Stone Age people” (such as those in Papua New Guinea, contacted only relatively recently) are likely more intelligent than Eurasians. Briefly, in the introduction to his Pulitzer-winning Guns, Germs, and Steel, Diamond suggests that for countless millennia, New Guineans’ minds have been naturally selected to successfully navigate unpredictable events such as endemic tribal warfare, natural disasters, food procurement and the like. In contrast, Eurasians have long been shielded from such constant environmental pressures by the widescale adoption of agriculture and the rise of centralized states. In Eurasia’s densely packed peasant societies, Diamond reasons, natural selection will therefore have focused more on disease resistance than on intelligence.

Diamond doesn’t develop this idea in any detail, rather he deploys it as a device, a throwaway rebuttal of long-standing “biological” claims about the superior intelligence of Europeans. Somewhat ironically, by doing, so Diamond challenges the established anti-racist consensus (articulated forcefully by evolutionary biologist Stephen Jay Gould) that natural selection has moulded the human body but not the modern human mind. Diamond shows how easy it is to challenge this liberal assumption—after all, why should natural selection only work to adapt human beings’ bodies to local environments and not their brains? Surely environmental challenges would also shape human cognitive behaviors in ways that enhance survival and reproduction.

In a nutshell, this illustrates the real reason why many liberal critics fear discussion of evolved human differences—that it will inevitably lead to the belief that such differences are not just skin deep, that they also extend to human brains and behavior. If debate can be stopped before it begins, we are less likely to lurch down this socially divisive slope. 

This is no idle concern. The late controversial psychologist Philippe Rushton used the same argument as Jared Diamond but came to the opposite conclusion; in Rushton’s evolutionary account, Eurasia presented a far more cognitively demanding environment for expanding human populations, providing the initial impetus for the high IQ scores recorded by, say, East Asians today.

usRushton’s Race, Evolution, and Behavior (published in the same year as Charles Murray’s and Richard Herrnstein’s incendiary study of intelligence, The Bell Curve) has come under harsh attack in academia. It epitomizes the liberal dread of Darwinian reasoning; in it, Rushton (sometimes using cherry-picked data) posits evolved genetic differences as the ultimate cause of modern racial inequalities, and of racial disparities in social phenomena such as crime, employment, wealth and educational achievement. 

Even among avowed human evolutionists, Rushton’s thesis has provoked severe condemnation: in one scathing review, sociobiologist David Barash opined, “Rushton argues at length … that by combining numerous little turds of variously tainted data, one can obtain a valuable result; but in fact, the outcome is merely a larger than average pile of shit.” 

Barash concluded: “Bad science and virulent racial prejudice drip like pus from nearly every page of this despicable book.” (It’s worth noting that Barash himself has faced similar censure for his evolutionary-informed stance on human behaviour – for instance, being portrayed as a misogynist apologist for the biological ‘naturalness’ of rape because of his own research into differences in male and female behaviour.)

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Jewish IQ and genes

Equally critical responses have greeted speculation of a genetic-biological aspect to so-called “Jewish genius.” Ashkenazi Jews (Jews who settled in Europe after leaving the Middle East during the first millennium), despite being a tiny .19% percent of the world’s population, make up more than 20% of all Nobel Prizes and 25% of the ACM Turing awards, have the highest SAT scores of any religious or ethnic group, and make up 23% of the student bodies at the prestigious Ivy League universities and 30 percent of the Ivy faculty. In every country with a significant Jewish population, the performance of Jews in high-achievement, high-paying careers has only increased in recent decades.

slysz lWhat’s going on? As Jon Entine notes in Abraham’s Children: Race, Identity and the DNA of the Chosen People, there is no evidence that high IQ was embedded in the genes of the early Israelites. The early Jewish population during the first millennium BCE was at times as large or larger than the citizenry of ancient Rome and Athens, but its intellectual contributions were not comparable. While Jews wrote the Bible, a singular and enduring contribution, the Greco-Roman world revolutionized art, science, and literature. What changed? Evolutionary pressures, Entine maintains.

In The 10,000 Year Explosion, anthropologists Gregory Cochran and Henry Harpending argue that enhanced intelligence is an evolved response to the specific conditions that Jews faced in Medieval Europe. Briefly, they suggest that for approximately 1000 years Ashkenazim were forced into intellectually demanding occupations such as money lending by the religious prejudices of the Christian majority. Moreover, the study of the Talmud, central to Jewish practices in the Diaspora, prioritized literacy. These cultural trends, combined with endogamous (in-group) marriage practices, fostered the mechanism for the natural selection of enhanced verbal and cognitive abilities in European Jews. The thesis was widely advanced in their highly controversial paper, The Natural History of Ashkenazi Intelligence (and discussed in detail in Jon Entine’s book, Abraham’s Children: Race, Identity and the DNA of the Chosen People).

Elsewhere in The 10,000 Year Explosion, and in an argument reminiscent of Diamond’s, Cochran and Harpending speculate that the growth of large agricultural populations in Eurasia, in addition to selecting for disease resistance, also increased the psychological passivity of those forced to live in close proximity with others and to cope with the day-to-day drudgery of farming. The flip side to this line of reasoning, though, is that that those human populations that lack such a history of “self-domestication” will also lack the same suite of evolved psychological behaviors. This potentially leads, the authors suggest, to difficulties adjusting to modern urban life.

The liberal objection to such speculative scholarship is obvious—it suggests that inequality is in some measure reflective of population differences and human biology. The victims of injustice (or, rather, their genes) are in part to blame. This is a fascinating theory, but sharply criticized by some as an example of what Stephen Jay Gould described as Darwinian “just so” storytelling: biological fairy tales that could be used to justify almost any form of social inequality as a product of the intertwining of genetics and history. 

Genetic warriors

Another example of this is the Māori “warrior gene” hypothesis. To briefly summarize the controversy: a small-scale genetic study focusing on addiction demonstrated an apparent higher frequency of an implicated gene allele in modern Māori (the indigenous people of New Zealand) relative to non-Māori participants. The specific allele, MAO-A, had earlier been dubbed the “warrior gene” due to its apparent association with aggressive behaviour in Rhesus macaque monkeys, with other monoamine oxidase (MAO) genes also linked to various behavioural disorders, including depression, mental retardation and risk-taking.

Credit: Whakareware Māori Living Village

In attempting to explain this seeming higher prevalence of MAO-A among Māori, the epidemiologists conducting the study, Rod Lea and Geoffrey Chambers, speculated that the gene may have been positively selected during the ocean voyaging and tribal wars that supposedly characterised the ancestral Polynesian migrations across the Pacific. They supported this hypothesis by pointing to the recognized “warrior tradition” in both historical and modern Māori culture. Perhaps predictably, this hypothesis was then reported in the popular media as a claim that contemporary Māori carry a “warrior gene”, making them prone to violence, criminality and risky behaviour (although Lea and Chambers denied this link).

Was their speculation on target? No way to know, hence its dismissal by some as a ‘just so’ hypothesis. As with other controversial theories of evolved cognitive and behavioral differences in human groups, the warrior gene hypothesis also faced legitimate scientific criticism for questionable methodology and insufficient evidence. Liberal critics are clearly right to fear the potential social fallout of such ideas becoming widely accepted: of certain communities being stigmatized as innately aggressive or criminal, say, or unable to adapt to modern life, or of a hierarchy of human groups inherently more or less intelligent.

Jon Entine is the founding executive director of the Genetic Literacy Project, and winner of 19 major journalism awards. He has written extensively in the popular and academic press on agricultural and population genetics. You can follow him on Twitter @JonEntine

Patrick Whittle has a PhD in philosophy and is a freelance writer with a particular interest in the social and political implications of modern biological science. Follow him on his website patrickmichaelwhittle.com or on Twitter @WhittlePM

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