Just follow the link
here.
But this shouldn't be the least controversial to people who have read a reasonable amount of evolutionary biology (Darwin, G. G. Simpson, Richard Dawkins, Matt Ridley, C.D. Darlington, etc.). Like the skeletal system, dentition, digestive system function, respiratory system function, or immune system function, nervous system function evolved. Unless human evolution is over, regional varieties of human will differ. It takes a (typically, Socialist) religious faith in functional equality of economically important traits among regional varieties of human to deny this. Doctrinaire Socialists are as susceptible to dogmatic fundamentalism as any creationist.