"Although there are now many more humans than chimps, in the past, human populations were much smaller, and may have been fragmented into even smaller groups," Bakewell told LiveScience. So random events would play a more dominant role than natural selection in humans.
Here is why: Under the process of natural selection, gene variants that are beneficial get selected for and become more common in a population over time. But genetic drift, a random process in which chance "decides" which alleles survive, also occurs. In smaller populations, a fortuitous break for one or two alleles can have a disproportionately greater impact on the overall genes of that population compared with a larger one. Chance events could also explain why the scientists found more gene variants that were either neutral and had no functional impact or negative changes that are involved in diseases. There is still much to learn, the scientists say, about human and chimp evolution. "There are possibly a lot of differences between human and chimps that we don't know about, [perhaps] because there are differences in chimps that nobody has studied; a lot of studies tend to focus on humans," Bakewell (see link) said. MORE - continued: http://pnews.org/ArT/WaR/ASup.shtml Hank Roth
