Scientists have long known that natives of southern Africa are genetically distinct from people in the rest of the world, but a new study in which the genomes of four African Bushmen and one Bantu were sequenced indicates that there is a much greater diversity among the populations there than had previously been suspected. Two Bushmen from different tribes living within walking distance of each other can have greater genetic differences than a European and an Asian. The study, which marked the first time that the DNA of a hunter-gatherer had been sequenced, found about 1.3 million new variants in the genetic sequences, accounting for about 1% of the total human genome. The Bushmen had genetic variants that distinguish them from other population groups. They were missing a gene for metabolizing lactose, were lacking a gene that promotes malaria resistance, had genes that gave them denser bones, greater strength and a greater ability to run short distances, and had another gene that promotes their ability to retain salt and water at high temperatures. The greater strength and sprinting ability of the Bushmen would be a clear advantage for survival in the arid Kalahari, as would the ability to retain water and salt. The lactose intolerance and lack of resistance to malaria, however, could be significant problems as more and more of the Bushmen are forced into agrarian societies where milk is a staple and the density of malaria-bearing mosquitoes is much higher than in the desert.
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