It's also important to acknowledge that genes which lead to success vary over time. 200 years ago the genes which lead to a median IQ of 100 chewed up an awful lot of pressure resources and did jack all to extend median Caucasian lifespans in Africa beyond 18 months. The brain is *incredibly* resource intensive. Meanwhile, the genes which lead to a median IQ of <80 survived pretty darn well in Africa. Those extra IQ points weren't effective in a resource and disease rich environment. Genes adapt to environmental pressures. They also adapt slowly, and the modern era of technology where IQ is king is only an eyeblink old in the grand scheme of human history.