Editing Race and intelligence (section)

===Racial admixture studies===
Most people have ancestry from different geographical regions. In particular, African Americans typically have ancestors from both Africa and Europe, with, on average, 20% of their genome inherited from European ancestors.<ref>{{harvnb|Bryc et al.|2009}}</ref> If racial IQ gaps have a partially genetic basis, one might expect black people with a higher degree of European ancestry to score higher on IQ tests than black people with less European ancestry, because the genes inherited from European ancestors would likely include some genes with a positive effect on IQ.{{sfn|Loehlin|2000}} Geneticist [[Alan Templeton]] has argued that an experiment based on the Mendelian "common garden" design, where specimens with different hybrid compositions are subjected to the same environmental influences, are the only way to definitively show a causal relation between genes and group differences in IQ. Summarizing the findings of admixture studies, he concludes that they have shown no significant correlation between any cognitive ability and the degree of African or European ancestry.{{sfn|Templeton|2001}}

Studies have employed different ways of measuring or approximating relative degrees of ancestry from Africa and Europe. Some studies have used skin color as a measure, and others have used blood groups. {{harvp|Loehlin|2000}} surveys the literature and argues that the blood groups studies may be seen as providing some support to the genetic hypothesis, even though the correlation between ancestry and IQ was quite low. He finds that studies by {{harvp|Eyferth|1961}}, Willerman, Naylor & Myrianthopoulos (1970) did not find a correlation between degree of African/European ancestry and IQ. The latter study did find a difference based on the race of the mother, with children of white mothers with black fathers scoring higher than children of black mothers and white fathers. Loehlin considers that such a finding is compatible with either a genetic or an environmental cause. All in all Loehlin finds admixture studies inconclusive and recommends more research.

Reviewing the evidence from admixture studies {{harvp|Hunt|2010}} considers it to be inconclusive because of too many uncontrolled variables. {{harvtxt|Mackintosh|2011|p=338}} quotes a statement by {{harvp|Nisbett|2009}} to the effect that admixture studies have not provided a shred of evidence in favor of a genetic basis for the IQ gap.