Scientists find traces of very first Americans

Across a span of 11,500 years, a baby is speaking to us.

Although she was just an infant when she died, her diminutive remains are helping researchers understand how ancient people first entered and moved around the Americas.

The little girl recently was given the name Xach’itee’aaneh T’eede Gaay (Sunrise Girl-Child) by indigenous people in the Alaskan interior who live close to the place where her body was found.

Archaeological evidence suggests her family buried her with care in a pit beneath the central hearth in their temporary home. They laid her to rest on a bed of ocher and placed offerings of weapons around her makeshift grave.

Centuries later, her tiny skeleton was unearthed during an archaeological dig, and, with the permission of local indigenous tribes, samples of her bones were sent off for DNA analysis. Scientists were stunned by what they revealed: This little girl was born into a previously unknown population of pioneers who were among the first to arrive in North America.

The discovery, reported Wednesday in Nature, has complicated the story of how humans spread throughout the Americas and brought it into clearer focus, said Ben Potter, an anthropologist at the University of Alaska-Fairbanks who worked on the new study.

“No one can deny that this makes our picture of the history of Native Americans more complex and more accurate than ever before,” he said.

David Reich, a geneticist at Harvard Medical School, hailed the new work as a crucial step toward better understanding how the earliest migrants to the New World diversified once they got here.

“This is an important finding, as it constrains possible scenarios for the early peopling of the Americas in significant ways,” he said.

The baby’s grave was discovered in 2015 in an archaeological site known as Upward Sun River in Alaska’s Tanana River Valley. It appears to have been a residential base camp where men, women and children remained for several weeks at a time, primarily in the summer months. The site was occupied multiple times, beginning about 13,000 years ago.

The remains of Xach’itee’aaneh T’eede Gaay date to about 11,500 years ago.

She was buried along with another female infant who appears to be a close relative, but not a sister, the researchers said. Genetic analysis shows that the two had different mothers.

It’s never easy to get usable DNA from ancient bones. But with Sunrise Girl-Child, the research team got lucky.

Her DNA was well-preserved in deep sediments, which made it easier for modern scientists to decode it.

Things didn’t go as well for the second infant. The research team was able to analyze enough of her nuclear DNA to confirm that the two girls were related. However, a previous study found that their mitochondrial DNA, which is inherited only from one’s mother, was different.

Next the authors compared the more complete genetic sequence from Sunrise Girl-Child with that of other ancient genomes, as well as a panel of DNA profiles from 167 populations around the world. The baby’s DNA was more closely related to presentday American Indians than to any other tested populations, followed by Siberians and East Asians.

That didn’t come as much of a surprise. There is broad agreement among anthropologists and archaeologists that the first people who came to America traveled over Beringia, a strip of land that connected northeast Asia with northwestern North America during the last ice age, when sea levels were lower.

The part that was shocking was the discovery that the baby girl was related equally to both groups of present-day American Indians — those who live in northern North America, including Athabaskan and Algonkian speakers, and those who live farther south.

For this to be true, she must have belonged to a third group of people who lived before the northern and southern American Indians split into genetically distinct groups, the researchers said. They dubbed the newly identified group the Ancient Beringians.

“This was brand-new,” Potter said. Scientists “simply didn’t have this population on the radar.”