Race Differences in Intelligence

I recently finished reading a very controversial book called Race Differences in Intelligence by Richard Lynn. The structure of the book can be broken down into two main parts. The first part is a survey of a wide variety of academic literature that shows that there are differences in the IQs of different races. The second part is where the author presents his arguments on why there is reason to believe that these differences are partly determined by genetics, and why this happened. The author claims the variation of IQ observed between the different races is due to the various climates in which different groups had to survive. In essence, his argument is the following: since colder climates are more difficult to survive in, groups living in those areas eventually developed higher IQs.

The following table lists the races ranked in ascending order of their intelligence levels, and gives their geographical location and their median IQs.


According to Lynn, there are 10 reasons to believe why the variation of intelligence between the different races are at least partly genetically determined:
  1. It is a principle of evolutionary biology that when sub-populations of a species become geographically isolated and occupy different environments, they become genetically differentiated and eventually diverge so much that they become different species. It is in accordance with this principle that the races have become genetically differentiated for all characteristics for which there is genetic variation, including body shape; color of skin, hair, and eyes; prevalence of genetic diseases; and blood groups. It is inconceivable that intelligence would be the single exception to these differences. Some racial differences in intelligence must also have evolved as a matter of general biological principle.
  2. The studies summarized in the table show a consistency of the IQs of the races in a wide range of geographical locations that can only be explained by some genetic determination.
  3. The races differ consistently in IQ when they live in the same environments. Thus, Africans in the United States, Britain, the Netherlands, and Brazil consistently have lower IQs than whites. 
  4. When babies from other races are adopted by Europeans in Europe and the United States, they retain the IQs characteristic of their race.
  5. Mixed-race individuals have IQs intermediate between those of the two parent races. Thus, in the Weinberg, Scarr, and Waldman (1992) study of children adopted by white middle class families, at the age of 17 years blacks had an IQ of 89, those of mixed black-white parentage an IQ of 98, and whites an IQ of 106 (Lynn, 1994c). When the amount of European ancestry in American blacks is assessed by skin color, dark-skinned blacks have an IQ of 85 and light-skinned blacks have an IQ of 92 (Lynn, 2002a), and there is a statistically significant association between light skin and intelligence.
  6. The IQs of races explain the extent to which they made the Neolithic transition from hunter gathering to settled agriculture. This transition was made completely by the more intelligent races: the Europeans, the South Asians and North Africans, the East Asians, the South-east Asians, and the Native Americans; to some extent by the Pacific Islanders, who were handicapped by living in small and dispersed populations on small islands; minimally by the Africans; but not at all by the Bushmen and Australian Aborigines, with IQs of 54 and 62, who have made virtually no progress in the transition from hunter-gatherers to settled agricultural societies. The only anomaly is the Arctic Peoples, with their IQ of 91, who remain largely hunter-gatherers, but this is due to their very small and dispersed populations and the harsh climate of the Arctic Circle.
  7. The IQs of races are consistent with their achievements in the development of early urban civilizations with written languages, systems of arithmetic, and codified laws as shown by Baker (1974), who has documented that only the East Asians, the Europeans, the South Asians and North Africans, and the Southeast Asians developed early civilizations.
  8. All the twin studies that have been carried out in Europe, India, and Japan, and on blacks and whites in the United States, have found a high heritability of intelligence in national populations. It is improbable that these high heritabilities within races could co-exist with the absence of any heritability for the differences between the races.
  9. There are race differences in brain size that are associated with differences in intelligence, and brain size has a heritability of 90 percent (Baare, Pol et al., 2001) (see also Rushton and Osborne, 1995). The only reasonable interpretation of this association is that the races with the higher intelligence have evolved larger brains to accommodate their higher IQs.
  10. The consistency of all the racial differences in so many different nations, in the development of early and later civilizations, and the high heritability of intelligence wherever it has been investigated, all need to be considered in terms of Popper's (1959) theory of the logic of scientific explanation. This states that a scientific theory generates predictions that are subjected to empirical testing. A strong theory has few assumptions and generates a large number of predictions that are empirically verified. If the predictions are discontinued the theory is weakened and may even be destroyed, although a single disconfirmation can generally be explained or the theory can be modified to account for it. For the problem of race differences in intelligence, the theory that these have some genetic basis explains all the numerous phenomena set out in the points listed above, and there are no serious anomalies. The theory that the race differences in intelligence are to a significant extent genetically based fulfills Popper's criteria for a strong theory. Those who assert that there is no evidence for a genetic basis of racial differences in intelligence betray a lack of understanding of the logic of scientific explanation.
Needless to say, I'm quite irritated by this book. First, I don't want to believe that certain races are simply more intelligent than others. Being born and raised in America, I have adopted the racial sensitivity that has made me highly suspicious of any claims of racial superiority. That said, what I want to believe is completely different than what is true, and so if we only consider Lynn's arguments, I have to say that they seem to be quite reasonable. Assuming that his facts are correct, I can't think of any fatal flaws to his logic. However, the second reason why I'm irritated by his work (which is my academic criticism) is that the author adopts IQ as the sole measure of intelligence. I can accept the fact that certain races have higher IQs and perhaps that these variations are partly genetically determined, but I don't accept that we can truly measure intelligence using an IQ test. An alternative to equating IQ to intelligence is the theory of Multiple Intelligences (MI), which I have found to be much more reflective of the capacities of human beings. Howard Gardner, the main proponent of MI theory, argues that all non-disabled human beings are born with the following intelligences: musical, bodily-kinesthetic, logical-mathematical, linguistic, spatial, interpersonal, intrapersonal, naturalist, and existential. Until advocates of race differences in intelligence incorporate MI theory and show that their conclusions still hold true, I don't accept the claim that certain races are more "intelligent" than others.