Saturday, August 4, 2012

Problems with the Cold Winters theory of intelligence


There is continuing controversy about inter-ethnic differences in IQ and why these might exist. Richard Lynn (Kanazawa, 2012; Richard Lynn, 1987) proposed that Europeans and Asians are more intelligent than Africans because during their evolutionary history they faced the challenge of surviving in environments featuring extremely cold winters. He claimed that survival in cold conditions 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.  

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 (2012) explains Lynn's theory with 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, that is, open grasslands, and so African hunters would have therefore needed to solve the problem of hunting without tree cover. Kanazawa (2012) 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 are known to hunt elephant and giraffe. Would not hunting these large animals pose adaptive problems involving coordination of hunting parties? 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 in cold climates producing fire 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 thousands of 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? I have never heard any scientist seriously propose that this is the case. The Neanderthal tool repertoire was much more limited than that of their Cro-Magnon contemporaries yet they somehow managed to survive for millennia with rather crude tools. Neanderthals do not seem to have developed any art forms, 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.
Were our Neanderthal cousins deep thinkers?

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. 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. He has argued that generally speaking, average brain size is correlated with average IQ within a given human population. 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 requires large populations to develop 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 were clearly 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 they have higher average IQs (Table 16.2).

  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 is no compelling reason 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. The explanation for why there are persisting inter-ethnic differences in mean IQ scores remains unclear (Neisser et al., 1996). Richard Lynn believes that these differences are due to evolved genetic differences between distinct racial groups but this view is not widely accepted in academia. His theory of cold winters as an explanation for this phenomenon does not seem at all plausible.


Follow me on Facebook, Google Plus, or Twitter.
© Scott McGreal. Please do not reproduce without permission. Brief excerpts may be quoted as long as a link to the original article is provided.  

References

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