White Americans are both genetically weaker and less diverse than their black compatriots, a Cornell University-led study finds.
Analyzing the genetic makeup of 20 Americans of European ancestry and 15 African-Americans, researchers found that the former showed much less variation among 10,000 tested genes than did the latter, which was expected.
They also found that Europeans had many more possibly harmful mutations than did African, which was a surprise.
“Since we tend to think of European populations as quite large, we did not expect to see a significant difference in the distribution of neutral and deleterious variation between the two populations,” said senior co-author Carlos Bustamante, an assistant professor of biological statistics and computational biology at Cornell.
It’s been known for years that all non-Africans are descended from a small group, perhaps only a few dozen individuals, who left the continent between 50,000 and 100,000 years ago.
But the Cornell study, published in the journal Nature Thursday, indicates that Europeans went through a second “population bottleneck,” probably about 30,000 years ago, when the ancestral population was again reduced to relatively few in number.
The doubly diluted genetic diversity has allowed “bad” mutations to build up in the European population, something that the more genetically varied African population has had more success in weeding out.
For example, Native Americans show even less genetic diversity than Europeans, having descended from a few thousand people who entered North America about 10,000 years ago.
That fact was reinforced by a larger-scale study, also published in Nature, led by scientists from the Universities of Michigan and Virginia who analyzed genetic samples of 485 individuals scattered around the globe whose DNA is recorded in a French databank.
As would be expected with the “out of Africa” theory, the researchers found Africans had the greatest amount of genetic diversity, followed in turn by Middle Easterners, then Europeans and South Asians at about equal levels, then East Asians.
Click here for an abstract of that study in Nature.
A third study, published in the journal Science on Friday, may be the most fascinating of all.
Native Americans have at least one closely related group in Asia—the Yakuts of eastern Siberia, who themselves are related to other hunter-gatherer Siberian tribes, some of whom build wooden teepees.
The Basques in northeastern Spain and southwestern France may be right to demand their own nation—they’re not closely related to anyone else. Surprisingly, neither are the residents of Sardinia off the coast of Italy.