leggi "In 1991 I extended my work on race differences in intelligence to other races. I concluded that the average IQ of blacks in sub-Saharan Africa is approximately 70. It has long been known that the average IQ of blacks in the United States is approximately 85. The explanation for the higher IQ of American blacks is that they have about 25 per cent of Caucasian genes and a better environment.

The theory I have advanced to explain these race differences in IQ is that when early humans migrated from Africa into Eurasia they encountered the difficulty of survival during cold winters. This problem was especially severe during the ice ages. Plant foods were not available for much of the year and survival required the hunting and dismembering of large animals for food and the ability to make tools, weapons and clothing, to build shelters and make fires. These problems required higher intelligence and exerted selection pressure for enhanced intelligence, particularly on the Orientals"
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