Race, Genes, Evolution, and IQ: The Key Datasets and Arguments

There is considerable variation in the mean IQ scores of human racial groups. Such group differences may be caused by genetic or environmental effects. Here we review and refute the claims of those who argue that mean IQ differences are the result of genetic effects, a claim which has seen a resurgence in recent years. We begin with data that question the notion that races vary in IQ and real-world achievement in a manner supporting a racial hierarchy. First, minorities of different genetic ancestry have comparable IQ and achievement levels in the US. Second, worldwide, we often see gaps as large as between White and Black Americans within single racial groups. Third, the Black-White achievement gap is entirely due to sex specific differences in achievement. There are, however, no sex specific mean differences in IQ. With respect to the magnitude of racial achievement gaps, they are well within the range of effects caused by socioeconomic factors, particularly those related to education. Further, when IQ tests do not reference past knowledge (particularly vocabulary), the IQ gap disappears. We then review work showing that mixed race persons do not typically show intermediate IQ, a key prediction of the genetic hypothesis. Finally, we review the three extant transracial adoption studies, which do not provide any support for a genetic explanation for group level differences in IQ. In sum, there is nothing about the nature of racial IQ gaps that suggests a genetic explanation, and the experimental work does not support a genetic explanation.