In the mid 2000s, years before I was famous, there was a lot of excitement in the HBD community about the genes, Microcephalin (MCPH1) on chromosome 8p23 and abnormal spindle-like microcephaly (ASPM) on chromosome 1q31. These genes are interesting because when they mutate they cause microcephaly (extremely small head and brain). In addition, they were extremely selected in the primate line leading to humans which makes sense because brain size roughly tripled in the past 4 million years of our evolution. In addition, allele D of MCPH1 emerged roughly 37,000 years ago which is roughly the time of the so-called great leap forward, when human behavior became widespread in people in Europe. Meanwhile allele D of ASPM emerged about 5,800 years ago, around the time of the World’s first civilization.
If all this weren’t enough to suggest these genes were linked to intelligence, they also seemed to largely fit the racial IQ pattern, with the genes spreading rapidly virtually everywhere except black Africa, and were perhaps the most rare among the pygmies.
However when race scholar Rushton himself investigated, he found no evidence the genes were linked to brain size (head circumference), IQ, or even pro-social attitudes. What advantage then did they confer to cause such extreme selection, and why did they emerge with the rise of intelligent behavior and in higher IQ races? My guess is they are linked to executive function.
Executive Function is a major part of intelligence ignored by IQ tests, yet it would not be ignored by natural selection because it enables you to adapt to dynamic situations by shifting attention in a flexible way. So whatever groups were selected for general intelligence (IQ) would also have been selected for Executive Function, but because EF is only weakly correlated with IQ, Rushton failed to find a link between IQ and these genes.