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Cold Winters and the Evolution of Intelligence

Lynn's theory of the evolution of intelligence does not fit the facts.

There is continuing controversy about inter-ethnic differences in IQ and why these might exist. One of the most heated areas of debate is what role if any is played by genetic differences between ethnic groups. Richard Lynn (Kanazawa, 2013; Lynn, 1987) proposed that because European and Asian environments feature extremely cold winters the inhabitants of these regions historically faced greater challenges to survival than Africans. He claimed that these survival challenges would have created selection pressures for greater intelligence. Africans, on the other hand, live in tropical conditions all year round and hence did not need as much intelligence. Lynn (2006) has presented data correlating the intelligence of different ethnic groups with the severity of their winter climates. However, there are some anomalies in his data and the theory itself is based on questionable assumptions.

In a recent paper on race differences in penis size, which I have critiqued elsewhere, Lynn (2013) claimed that there is “widespread consensus” about the cold winters theory. In support of this assertion, he cited papers by Satoshi Kanazawa, Donald Templer, and himself. Widespread consensus indeed! All of these authors are proponents of “race realism,” the belief that differences between ethnic groups in intelligence and other factors have a genetic and evolutionary basis. This is like citing the opinions of a group of one’s friends as representing accepted mainstream thinking. In spite of Lynn’s claims, the cold winters theory is a speculative one that seems to be based mainly on cherry-picking of evidence to support race realist ideas and ignoring everything else that does not fit the theory.

The theory of cold winters proposes that survival in colder climates poses two evolutionarily novel problems that would have required high intelligence to solve: finding food and keeping warm (Kanazawa, 2012). Kanazawa makes fairly sweeping statements about how easy it was to obtain food in Africa, whereas people in more northerly latitudes had to rely more extensively on hunting, which presumably required more intelligence. He cites a statement by Lynn “that hunting in the grasslands of Eurasia is more difficult than hunting in the woodlands of Africa because the former does not provide cover for the hunters.” This claim seems rather bizarre in light of the fact that modern humans are thought to have evolved on the African savannah, consisting of open grasslands. African hunters would therefore have needed to solve the problem of hunting without tree cover long before modern humans left Africa. Kanazawa goes on to elaborate why Eurasian hunters were supposedly more sophisticated than their African counterparts:

Effective hunting thus presents a whole host of new adaptive problems for our ancestors in Eurasia to solve, including the coordination of different hunters for a single goal and the manufacture and use of hunting weapons. These problems were largely unencountered by their counterparts left behind in sub-Saharan Africa. These novel adaptive problems exerted strong selection pressures for higher intelligence.

Really? Does Kanazawa suppose that ancient African peoples did not know how to coordinate hunting parties or manufacture and use hunting weapons? Recent evidence indicates that humans have been hunting for at least two million years. Modern pygmies and Bushmen[1] are known to hunt elephants and giraffes. Would not hunting these large animals pose adaptive problems involving coordination of hunting parties? Cooperative hunting among the !Kung San people of the Kalahari Desert in Africa is well documented by anthropologists. Furthermore, some non-human carnivores, such as lions and wolves, hunt in coordinated packs with admirable efficiency. Although these animals are relatively intelligent I do not think anyone would seriously suppose that they require the intellectual capacities of humans to perform these feats.

Kanazawa argues that producing fire in cold climates is more difficult because there are fewer natural brush fires where fire can be obtained without making it. Also, in cold climates producing warm clothing and adequate shelter is more difficult. But what evidence is there that early humans needed a high level of intelligence to do these things? Neanderthals lived in Ice Age conditions for a hundred thousand years and therefore faced these exact problems. Furthermore, Neanderthals were known to hunt European megafauna. Somehow they learned how to coordinate hunting parties to kill very large, very dangerous animals. Does this mean they were more intelligent than the first modern humans living in Africa? Although there is debate about just how intelligent Neanderthals were, all populations of modern humans, even the most “primitive” hunter-gatherers, appear to have developed a more sophisticated culture than that demonstrated by Neanderthals. Neanderthals seem to have lacked the capacity for innovation and creative thinking possessed by modern humans. Neanderthals do not seem to have developed any art forms[2], yet all races of modern humans, even the ones Lynn considers the least intelligent have developed art. Lynn (2006) acknowledges that anatomically modern humans first appeared in Africa. Yet he does not explain why it is that the modern human race that evolved in tropical Africa developed greater intelligence and cognitive sophistication compared to their Neanderthal relatives who had been surviving in harsh Ice Age conditions for so many millennia.

Lynn (2006) presents data on IQ, brain size, and winter temperatures for a wide range of human racial groups to support his theory that colder winters are associated with higher IQ and larger brains. He has argued that generally speaking, average brain size is correlated with average IQ across human populations. However, he does note anomalies in the data. The peoples of the Arctic endure the harshest winter conditions of all. Lynn’s hypothesis would seem to predict that they would have the highest intelligence and the largest brain size of any race. Lynn’s review found that on average they did have larger brains than any other race. However, the median IQ of Arctic peoples according to Lynn’s data is 91. This is within the normal range but clearly not ‘superior’. Arctic people have been found to have unusually strong visual memory that exceeds that of Europeans. Europeans who have travelled with the Inuit have remarked upon their extraordinary ability to traverse apparently featureless terrain and closely observe the smallest landmarks and memorise their spatial locations. Lynn argued that this enhanced visual memory is a result of natural selection in their Arctic environment. Strong visual memory has also been noted among desert-dwelling Australian Aboriginals, where it may have been an adaptation to life in a desert environment (Kearins, 1981).

Lynn (2006, p. 144) argued that high intelligence can only evolve in large populations because mutations, being chance events, are more likely to occur in large populations. Arctic people have smaller populations than Asians or Europeans and therefore mutations beneficial to intelligence did not occur. He argues that in Arctic peoples some of their larger brain size may be devoted specifically to visual memory. Strangely enough, he claims that Australian Aboriginals have smaller brain sizes compared to most other races, yet like Arctic peoples some Aboriginal tribes have apparently developed enhanced visual memory. To be fair, at least one study reported that Australian Aboriginals had a larger right visual cortex than Europeans, a part of the brain associated with spatial ability. He does not explain why natural selection among Arctic peoples would result in larger brain sizes or enhanced visual memory yet the same evolutionary pressures associated with a cold environment would not also produce higher intelligence. Arctic peoples have clear physical adaptations to the cold, such as short, stocky bodies well-suited to conserving heat. Additionally, some scientists have argued that a large brain is an adaptation to the cold that also helps to conserve heat. Neanderthals are striking for having had larger average brain sizes than modern humans, which has been argued to be an adaptation to the cold climate, yet they appear to have been less cognitively sophisticated than modern humans. His argument about beneficial mutations occurring only in large populations seems like nothing more than special pleading. Furthermore, he acknowledges that some races, such as Pacific Islanders have smaller brains than Australian Aboriginals, yet the former have higher average IQs than the latter (Table 16.2 of his book).

When anatomically modern humans first appeared in tropical Africa, more primitive hominids, such as Homo erectus, had been living throughout Eurasia for over a million years. If cold winters were a stimulus to the development of greater intelligence it is not clear why modern humans developed such high intelligence in a tropical climate. Furthermore there are no compelling reasons to suppose that survival in cold climates actually requires higher intelligence than survival in the tropics. It could be argued that survival in the tropics poses special challenges that would require intelligence, such as coping with tropical diseases and parasites (Sternberg, Grigorenko, & Kidd, 2005). The !Kung San people of the Kalahari Desert traditionally lived for thousands of years in one of the harshest environments on earth, where even finding water can be a struggle. Yet Lynn does not credit them with much intelligence (see Table 16.2 of his book). Sternberg et al. (2005) point out that it is easy to simply make up speculative “just so” stories to support the notion that survival in any particular environment posed special challenges that required greater intelligence. One could just as easily argue that survival on a tropical island in the Pacific requires high intelligence because of the special skills required to navigate on the open ocean. All sorts of human environment seem to present challenges that might require intelligence to negotiate successfully.

The reasons why there are persisting inter-ethnic differences in mean IQ scores remain unclear (Neisser et al., 1996). Environmental differences between ethnic groups, such as nutrition, education, and economic development need to be taken into account. Richard Lynn believes that these IQ differences are due to evolved genetic differences between distinct racial groups but this view is not widely accepted in academia, contrary to Lynn’s claims. His theory of cold winters as an explanation for this phenomenon does not seem at all plausible and is based on little more than speculation.


[1] These names are used by Lynn and are used here for convenience and are not intended to be pejorative.

[2] Some anthropologists might debate this. Nevertheless, evidence for Neanderthal art is sparse indeed, yet there is clear evidence of modern humans producing art in all areas of the world.

Related reading:

Articles discussing "race realism"

Articles discussing intelligence and related concepts

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© Scott McGreal. Please do not reproduce without permission. Brief excerpts may be quoted as long as a link to the original post is provided.


Kanazawa, S. (2012). The evolution of general intelligence. Personality and Individual Differences, 53(2), 90-93. doi: 10.1016/j.paid.2011.05.015

Kearins, J. M. (1981). Visual spatial memory in Australian Aboriginal children of desert regions. Cognitive Psychology, 13(3), 434-460. doi: 10.1016/0010-0285(81)90017-7

Lynn, R. (1987). The intelligence of the Mongoloids: A psychometric, evolutionary and neurological theory. Personality and Individual Differences, 8(6), 813-844. doi: 10.1016/0191-8869(87)90135-8

Lynn, R. (2006). Race differences in intelligence: an evolutionary analysis: Washington Summit Publishers.

Lynn, R. (2013). Rushton’s r–K life history theory of race differences in penis length and circumference examined in 113 populations. Personality and Individual Differences, 55(3), 261-266. doi:

Neisser et al. (1996). Intelligence: Knowns and Unknowns. American Psychologist, 51 (2), 77-101 DOI: 10.1037//0003-066X.51.2.77

Sternberg, R. J., Grigorenko, E. L., & Kidd, K. K. (2005). Intelligence, Race, and Genetics. American Psychologist, 60(1), 46-59. doi: 10.1037/0003-066X.60.1.46