[Warren Whitmore]

In sir Francis Galtons book "Hereditary Genius" He worked very hard at this question. He traveled Africa extensivly in many cases being the first European to have been seen by the various tribes. His data suggested (in shock from the scientific community at the time) was that the disparity among the various tribes was huge. Some tribes being equal or smarter than Europeans and some barly functional. Given that he was a great statistician and scientist (he developed the math for regression to the mean). I suspect he was right.