About 11,000 years ago, a man died in what is now Nevada. The body was placed in a blanket and buried at a place called Spirit Cave.
Recent research and scientific discoveries, including new research at Spirit Cave, are changing what we know about prehistory.
This research lends astonishing new detail to the story of human migration and when humans spread across the Western Hemisphere. Using DNA analysis, scientists have examined remains of ancient people uncovered at sites throughout the Americas.
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The peopling of the Americas still holds much mystery. It is believed that people moved into the New World sometime during the last ice age, traveling from Siberia to Alaska across a land bridge now submerged under the Bering Sea. These ancient explorers spread southward, eventually reaching the tip of South America.
But, there are at least two schools of thought about who arrived first. Some research indicates the first Americans crossed the Bering Land Bridge and spread south from Alaska. This is known as the “Clovis-first theory.” Spearpoints, called Clovis points, were found near Clovis, New Mexico. Scientists associated these Clovis spearpoints, first identified in 1933, with stone tools used by ancient hunters in Siberia.
A second theory says that daring explorers in small boats skirted the ice sheets and eventually made their way south along the west coast of North America. Researchers who accept this theory think there were probably several waves of prehistoric humans from Asia arriving in the previously uninhabited New World.
While most experts agree that early humans migrated by boat or land bridge from northeast Asia to Alaska and North America, what happened next is still a mystery. And that is why the new research is so revealing. Scientists looking at DNA evidence are beginning to paint a picture of what happened and how ancient people quickly spread throughout two vast continents.
Until recently, geneticists could offer only limited insight into these vast migrations. There just was not enough DNA evidence. During the past several years, however, that has changed. Scientists have examined hundreds of specimens from all over North and South America, including the mysterious mummy found at Spirit Cave. This means the picture of ancient human migration is coming into focus.
“Living Native Americans descend from two major ancestral groups,” according to a recent report in The New York Times summarizing the new discoveries. Sometime after crossing from Asia to the Americas, these hardy people split into two separate groups.
The first group, a northern branch, spread eastward and remained close to the retreating glaciers where they would continue to hunt mammoths and other ice-age species. New DNA research shows connections to Native American communities in Canada, such as the Athabascans, along with some tribes in the United States like the Navajo and Apache.
Meanwhile, a second and larger group spread out to the south. The southern branch included ancestors of other tribes currently living in the United States, as well as indigenous people in Central America and South America.
“Now, this is the grist for archaeologists,” Ben Potter of the University of Alaska said to The New York Times. Grist is a word that means the central point or meat of an issue. “Holy cow, this is awesome,” Potter said when describing the new research.
Genetic data now suggests that the southern group spread swiftly across much of the New World, all the way to South America, and that this happened about 14,000 years ago. This rapid expansion may have taken only a few centuries.
“It’s basically an explosion,” says Dr. Eske Willerslev, a geneticist at the University of Copenhagen.
Dr. Willerslev studied the remains of an 11,500-year-old girl found in eastern Alaska. He also examined a 9,000-year-old body from western Alaska. Willerslev and his colleagues first described their evidence in January in the journal Science.
“The earliest known arrivals from Asia were already splitting into recognizably distinct groups,” says Willerslev. “Some of these populations thrived, becoming the ancestors of indigenous peoples throughout the hemisphere.”
It turns out, according to the new discoveries, the ancient people of the Bering Land Bridge region separated from the ancestors of living indigenous people in the Americas about 20,000 years ago. New findings indicate they endured for several thousand years after that. But then they disappeared, leaving no known genetic trace in today’s living people.
But another wave of migrants from Siberia arrived and did not stop in Alaska. They kept moving, eventually arriving south of the big glaciers. Then they split into at least two branches. One group turned north into Canada while the other branch took a remarkable journey south.
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New research posted on the website cell.com demonstrates this point. For instance, DNA from a site in Montana is associated with Clovis culture. This same DNA is also heavily represented in present-day Central and South Americans and in ancient Californians. All this points to several successive waves of human migration.
“Such patterns suggest that these groups do not entirely descend from a single homogeneous population and instead derive from a mixture of populations,” according to the website.
What’s more, some people in modern Brazil show DNA characteristics similar to people called “Australasians.” This could mean explorers in boats from islands in the Pacific might have reached South America.
So, while all this new information solves a lot of questions, there remains even more answers to be discovered. Scientists will continue to unravel mysteries like the famous mummy from Spirit Cave.
[Sources: The New York Times; History.com; Cell.com; Science]