Ancient DNA Ties Native Americans From Two Continents To Clovis
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The mysterious Clovis culture, which appeared in North America about 13,000 years ago, appears to be the forerunner of Native Americans throughout the Americas, according to a study in Nature. Scientists have read the genetic sequence of a baby from a Clovis burial site in Montana to help fill out the story of the earliest Americans.
Until now, archaeologists have had to rely mainly on tools made of stone and bone, and other artifacts to tell the story of human migration about 15,000 years ago to the new world.
Now that story is bolstered with some dramatic, ancient DNA, extracted from the remains of a 1-year-old boy who died in present-day Montana more than 12,000 years ago.
That's the only human skeleton known from a brief but prolific culture in the Americas called Clovis.
"Clovis is what we like to refer to as an 'archaeological complex,' " says Michael Waters, an archaeologist at Texas A&M University. That complex is defined by characteristic tools, he says.
The Clovis artifacts were common for about 400 years, starting about 13,000 years ago. But at this point, there is only one set of human remains associated with those sorts of tools: that of the baby from Montana.
"So this genetic study actually provides us with a look at who these people were," Waters says.
The most obvious conclusion from the study is that the Clovis people who lived on the Anzick site in Montana were genetically very much like Native Americans throughout the Western Hemisphere.
"The Anzick family is directly ancestral to so many peoples in the Americas," says Eske Willerslev, from the University of Copenhagen. "That's astonishing!"
He led the effort to read that genome. The genes reveal that early Americans are the product of two lineages that most likely met and interbred in Asia before making the trek across the Bering land bridge.
"So this strongly suggests that there was a single migration of people into the Americas," Waters says. "And these people were probably the people who eventually gave rise to Clovis."
The finding contradicts a long-shot hypothesis that Clovis' ancestors actually came from Europe, not Asia. But it leaves many other questions about Clovis unresolved.
The artifacts from this culture are found from Washington state to Florida and many places in between. But the culture also disappeared suddenly, around 12,600 years ago. Waters doesn't find all of that so mysterious.
"People change all the time and cultures change all the time and technologies change," Waters says. "And they change because people are adapting to new environments and changes in climate."
"And at the end of the Clovis time period, 12,600 years ago, when this child was buried, the climate was changing. It was the beginning of the Younger Dryas cold snap. This is when you start seeing a lot of cultural differentiation taking place," Waters says.
The DNA evidence now makes clear that the people who used Clovis tools lived on, even though they left their old technology behind. But the Clovis genes give only a broad-brush view of how and when migrations through the Americas took place.
"We have no idea exactly where the U.S. fits in this pattern," Willerslev says. "And to be completely honest, we have no idea how they actually moved through time, these different groups throughout the continent. In order to answer that question there's only one way to go, and that is sequencing more genomes from ancient remains."
That will require, among other things, cooperation with native peoples.
In the case of the Clovis child, the archaeologists worked closely with modern tribes to make sure the scientists were treating the remains appropriately. The Clovis infant is to be re-buried later this year, on the property where he was unearthed.
Source: NPR [http://www.npr.org/2014/02/13/276021092/ancient-dna-ties-native-americans-from-two-continents-to-clovis?ft=3&f=1003,1004,1007,1013,1014,1017,1019,1128]