January 24, 2019

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.

On Thursday, a team of scientists reported that they had successfully recovered the man’s entire genome — by itself an important scientific development. But the man from Spirit Cave is not alone.

This week, three international teams of scientists have published studies of DNA recovered from 70 other ancient people in the Americas.

Five years ago, scientists had retrieved just one ancient human genome from the entire Western Hemisphere: that of a 4,000-year-old man discovered in Greenland. With the latest batch, the total has reached 229.

The genomes were obtained from the teeth and bones of people who lived from Alaska to Chile, from the coastal tropics of Belize to the high Andes. Hidden in this DNA are important discoveries about how humans spread through the Americas thousands of years ago.

Earlier studies had indicated that people moved into the Americas at the end of the last ice age, traveling from Siberia to Alaska across a land bridge now under the Bering Sea. They spread southward, eventually reaching the tip of South America.

But the new genetic findings have given researchers a much sharper picture. The earliest known Americans were already splitting off into recognizably distinct groups.

Some of these groups thrived, becoming the ancestors of indigenous people throughout the Western Hemisphere. Some died out entirely, leaving no trace save for what can be discerned in ancient DNA.

The new research hints at dramatic chapters in the people of the Americas that archaeology has not yet documented.

“It’s basically an explosion,” Dr. Willerslev said.

The man from Spirit Cave in Nevada belonged to this so-called southern branch of migrants. Dr. Willerslev also found that the man was closely related to a 12,700-year-old boy found on the other side of the Rocky Mountains in Montana.

Initially, the tribe was opposed to looking for DNA in the skeleton, because scientists would have to destroy much of it. Dr. Willerslev met with the tribe and explained that he would require only a tooth and 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 to turn over the skeleton to the tribe. They buried the man from Spirit Cave at an undisclosed location last year.

Ms. Downs wouldn’t rule out similar studies in the future, but said each request would require careful consideration.

“It’s all going to be on a case-by-case basis,” she said. “The main thing is our respect for the remains.”

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