Saturday, March 25, 2006

"Race Differences in Intelligence: An Evolutionary Analysis"

Review of Professor Richard Lynn's new book also posted here.

It would be difficult to fail to discriminate between Pygmies, Swedes, Japanese, American Indians and Australian Aborigines. Wearing evolutionary spectacles, the physical differences are clear racial adaptations to different environmental conditions, with climatic adaptations being particularly evident. Why would levels of intelligence not also have been differentially selected for between races?

Chapter 1 defines ‘intelligence’ and motivates why IQ is a measure of it. Chapter 2 justifies the concept of ‘race’ - depressing that this is thought to be necessary - and makes the argument of the first paragraph above.

Chapters 3 - 12 then itemise in great detail the results of numerous intelligence tests given to nine racially-distinguished populations: Europeans; Sub-Saharan Africans; Bushmen (South Africa) and Pygmies; South Asians (Middle-East, India, Pakistan) and North Africans; Australian Aborigines; Pacific Islanders; East Asians (China, Japan); Arctic People and Native Americans.

Base-lining Europeans at IQ = 100, Sub-Saharan Africans come out at around 67. Corrected for poor environmental conditions, Lynn estimates the genotypic IQ (the mean IQ Africans would have if raised in the same environment as Europeans) as around 80. Conversely, East Asians seem to have IQs centred around 105 (p. 130) while some populations of Ashkenazim Jews have mean IQs between 107-115 (p. 94).

Chapters 13-17 summarise racial differences, and propose an explanation based on the geographic radiation of homo sapiens out of Africa, the resulting geographical isolation of sub-populations, and the impact of two ice-ages (the first from 70,000 to 50,000 years ago, and then the more severe Wurm glaciation, 28,000 to 10,000 years ago). These culled the less-intelligent in those racial groups most exposed to arctic conditions as well as driving the more obvious physiological adaptations. The East Asians were particularly stressed by harsh conditions north of the Himalayas and east of the Gobi Desert.

I have some quibbles. Lynn’s timeline of geographic dispersal makes no mention of the Toba event, 70-75,000 years ago, which was said to have created a genetic bottleneck. If today’s races emerged from a radiation out of east Africa which post-dated that event, how would that affect the argument?

Secondly, the early evolution within east Africa (p. 225) is poorly argued. The contemporary IQ of 67 is not the one to use, as it factors in present-day malnutrition. In the ‘environment of evolutionary adaptedness’, this would not have been the case, so why not use 80? Lynn then appears to suggest there is a ‘continual directional selection for intelligence’ based on its utility, as if species always got smarter and smarter. However intelligence comes with large costs, in terms of the energy required for big brains, so one would expect instead an equilibrium where a species is no smarter than it has to be. So rather than a drift to smartness in Africa, isn’t it more likely that we saw waves of replacement populations radiating from groups who got smarter in more isolated niches where they were stressed more?

This is not a coffee-table read. It is somewhere between a scientific book for the academic community and a popularisation. I think Lynn hopes to move the goal posts so that we can move onto some of the interesting consequential issues clearly identified in his research programme. If at times he seems to stray into IQ-reductionism, then this is probably symptomatic of the existing research community being currently below critical mass.

There may well be public policy implications of the research results aggregated, summarised and theorised in this book. But they are rightly not addressed here.