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Crossing From Asia, the First Americans Rushed Into the Unknown

Crossing From Asia, the First Americans Rushed Into the Unknown

Nearly 11,000 years ago, a man died in what is now 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 70 other ancient people that were discovered throughout the Americas. The findings astonishing detail to a story once lost to prehistory: how and when people spread across the Western Hemisphere.

The earliest known arrivals from Asia have been divided into recognizably distinct groups, the research suggests. Some of these populations thrived, becoming the ancestors of indigenous peoples throughout the hemisphere.

But other groups died out, leaving no trace for what can be discerned in ancient DNA. Indeed, the new genetic research hints at many dramatic chapters in the peopling of the Americas that has archaeology 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 had indicated that people were moving into the Americas at the end of the last ice age, traveling from Siberia to Alaska across a country bridge now under the Bering Sea. They spread southward, eventually reaching the tip of South America.

Until recently, geneticists could offer little insight into these fixed 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 teeth and bones discovered throughout the Americas.

"It's basically an explosion," Dr. Willerslev said.

The man from Spirit Cave in Nevada belongs to this so-called southern branch of migrants. He 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.

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 is obviously, how did this happen?" Willerslev said.

Perhaps another group of Asians entered the Americas long before the ancestors of the man from Spirit Cave and other early Native Americans. Maybe they are interbred with people in the Amazon before disappearing altogether.

Or perhaps a few of the early members of the southern branches have survived through the generations.

The new rush of genetic samples reflects an improving relationship 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, the Fallon Paiute-Shoshone, did not learn anything until 1996. For years they fought for its repatriation.

"It's utterly disrespectful," said Rochanne L. Downs, a member of the tribe's cultural committee. "If someone went into Arlington Cemetery and dug the grave or their medals, there would be an outrage."

Initially, the tribe was opposed to looking for DNA in the skeleton, because scientists would have to destroy much of it. Dr. Willerslev with the tribe and explained that he would require only a small piece of ear bone.

The tribe agreed to give him one shot at finding DNA in 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 the Spirit Cave at an undisclosed location last year.

Ms. Downs would not rule out similar studies in the future, but said that every 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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