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Nearly 11,000 years ago, a man died in Nevada. Wrapped in a rabbit-skin blanket and reed mats, he was buried in a place called Spirit Cave.
Now scientists have recovered and analyzed his DNA, along with that of other ancient people. The findings lend astonishing detail to a story that was lost to prehistory: how and when humans spread across the Western Hemisphere.
The earliest known arrivals from Asia were already splitting into recognizably distinct groups, the research suggests. Some of these thrived populations, becoming the ancestors of indigenous peoples throughout the hemisphere.
But other groups died out entirely, leaving no trace for the future. Indeed, the new genetic research hints at many dramatic chapters in the peopling of the Americas that archeology has yet to uncover.
"Now, this is the grist for archaeologists," said Ben Potter of the University of Alaska, who was not involved in the new papers. "Holy cow, this is awesome."
Earlier studies have been reported that have moved into the Americas at the end of the last age, from Siberia to Alaska across the land under the Bering Sea. They spread southward, eventually reaching the tip of South America.
Until recently, geneticists could offer little insight into these vast migrations. Five years ago, just one ancient human genome had been recovered in the Western Hemisphere: that of a 4,000-year-old man discovered in Greenland.
The latest batch of analyzes, published in three separate studies, marks a turnaround. In the past few years, researchers have recovered the genomes of 229 ancient people from all over the Americas.
The first, described in January by Eske Willerslev, a geneticist at the University of Copenhagen, was an 11,500-year-old girl whose remains were found in eastern Alaska.
The second was discovered in Alaska, and lived 9,000 years ago, Dr. Willerslev and his colleagues reported on Thursday in the journal Science.
The Ancient Beringians separated from the ancestors of living indigenous people in the Americas about 20,000 years ago. The new findings suggest they endured for several thousand years. Then they disappeared, leaving no known genetic trace in living people.
But another wave of migrants from Siberia did not stop in Alaska. They kept moving, eventually arriving at the ice age. Then they split into two branches.
One group turned and headed north, following the retreating glaciers in Canada and back to Alaska. The other branch took a remarkable journey south.
The genetic data suggest that this group spreads over much of North America and South America about 14,000 years ago. The expansion may have taken only centuries.
"It's basically an explosion," Dr. Willerslev said.
The man from Spirit Cave in Nevada belonged to this so-called southern branch of migrants. He also was closely related to a 12,700-year-old boy found on the other side of the Rocky Mountains in Montana, Dr. Willerslev also found.
But the man from Spirit Cave has also been released in Brazil, on the other side of the equator.
David Reich of Harvard University and his colleagues found a similar pattern in their own research, published on Thursday in the journal Cell.
"We agree that this must be a rapid radiation," said Dr. Reich.
Starting about 9,000 years ago, both teams found, more waves of people moved southward. Dr. Willerslev's research suggests the new arrivals mixed with older South American populations.
Dr. Reich, on the other hand, who has lived in South America.
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The new research also reveals instances of remarkable continuity, which are spanned thousands of years.
Dr. Willerslev and his colleagues compared the genome of man from Nevada's Lovelock Cave, who lived as recently as 600 years ago.
All of these people were closely related, his team found, despite being separated by 10,000 years of history.
A similar bond was found in the Andes. John Lindo of Emory University and his colleagues analyzed 6,000 and 1,400 years ago.
The researchers estimate that people who lived above 7,500 feet in the mountains were separated from the lowland populations between 9,200 and 8,200 years ago. Today, the mountain people still show a strong genetic link to the ancient remains.
"This is not something that you see in most other regions of the world," said Dr. Reich.
In 2015, Dr. Reich and his colleagues found that some living people in the Amazon carry some DNA that is most likely to be affected by this phenomenon.
The researchers speculated that their ancestry included an unknown group, which the scientists called Population Y, who separately made their way into the Americas.
In their new study, Dr. Reich and his colleagues found no trace of Population Y – But Dr. Willerslev's team succeeded in identifying their DNA in some of the 10,400-year-old skeletons in Brazil.
"The million-dollar question obviously is, how did this happen?" Dr. Willerslev said.
Perhaps another group of Asians entered the Americas long before the ancestors of the man from Native American Spirit Cave. Maybe they interbred with people in the Amazon before disappearing altogether.
Or perhaps a few of the early members of the southern branch of the family have survived.
The new rush of genetic samples is improving relations between scientists and indigenous peoples. For decades, many tribes rejected requests for DNA from researchers.
The man from Spirit Cave, for example, was dug up by archaeologists in 1940 and stored in a museum. The local tribe, Fallon Paiute-Shoshone, did not learn the body until 1996. For years they fought for their repatriation.
"It's utterly disrespectful," said Rochanne L. Downs, a member of the tribe's cultural committee. "If someone went to Arlington Cemetery and took the medals, there would be contempt."
Initially, the tribe was opposed to DNA in the skeleton, because scientists would have to destroy much of it. Dr. Willerslev says with the tribe and explained that it would require a tooth and a small piece of bone.
The tribe agreed to give a one-on-one discovery to the Spirit Cave remains.
Dr. Willerslev's results led the Bureau of Land Management to turn over the skeleton to the tribe. They buried the man from Cave Cave at an undisclosed location last year.
Ms. Downs would not rule out similar studies in the future, but said each request would require careful consideration.
"It's all going to be a case-by-case basis," she said. "The main thing is our respect for the remains."
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