Tuesday, February 4, 2014

Super Bowl ads, Black Death, and Neanderthal bloodlines

While some Americans grumble over Cheerios and Coca-Cola ads depicting a multi-ethnic country, and Bill Nye debates evolution with the founder of the Creation Museum, scientists are making genetic discoveries that just so happen to be relevant to these news cycles.

Researchers find signs of western Eurasian genes in southern African Khoisan tribes
The Khoisan tribespeople of today still live much as their ancestors did—they are hunter-gathers who are also pastoralists—they are most familiar to westerners as the people who speak with distinctive clicking noises. Until now, they were believed to have the purest African gene pool due to their thousands of years of isolationist practices.

The team acquired DNA samples from 32 people living in Khoisan tribes in southern Africa—an analysis revealed Eurasian gene segments in all of them. But that wasn't the end of the story. To understand how the gene fragments got into the Khoisan tribespeople, the researchers turned to archeological and linguistic evidence to build a possible time-line of events. In so doing, they've found what they believe to have been a migration back into Africa by people of the Middle East (ancestors of the people that migrated to Europe and Asia) approximately 3000 years ago. Those people made their way to various parts of the continent, including a part of eastern Africa from which the Khoisan tribespeople had migrated south approximately 900 and 1800 years ago.

The researchers found something else—the Khoisan tribespeople also had snippets of Neanderthal DNA in their genes as well—courtesy of their Eurasian heritage.
Black Death likely altered European genes
Netea and his colleagues made their discovery by scanning almost 200,000 single-nucleotide polymorphisms (SNPs), or short segments of DNA that vary among people. They tested people from Romania, as well as Roma people. For social and economic reasons, Netea said, the Roma have lived among Europeans since about A.D. 1000, without much interbreeding between the two groups. That gives researchers a rare opportunity to study two genetically distinct populations in one geographical region.

The researchers looked for genetic variations that appeared in both Europeans and Roma people. Then, they took that list and crossed off the genetic variations that also appeared in a population of northwest Indians, to rule out evolutionary change that originated outside Europe.

The result was a list of about 20 genes that show evidence of convergent evolution between Europeans and Roma — meaning the two groups started out different but evolved to look more similar because of pressures in their environment.
Neanderthal DNA shows that man's family tree is decidedly gnarled
But I noticed something odd and revealing about some of the headlines on last week’s stories: They suggested that everyone reading the story had a bit of Neanderthal in his or her lineage. Thus the headline on the New York Times online story: “Neanderthals Leave Their Mark on Us.”

Us? As the story made clear, tiny amounts of Neanderthal DNA had been found in “Europeans and Asians” but not in sub-Saharan Africans whose ancestors stuck around when their cousins left the continent. I was reminded of the old Tonto/Lone Ranger joke: “What do you mean we, white man?”

(The Los Angeles Times headline was “Neanderthal genes helped modern humans evolve, studies suggest.” More accurate, though it would have been better to say “some modern humans.”)

I’m not saying the New York Times headline writer — and others who referred to people with Neanderthal DNA as “we” or “you” or “us” — were racist or captives to white privilege. But they were careless.
Let's hope the science skeptics can evolve from here.

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