Researchers look for ancient human remains in northern Greenland.

Claus Andreasen

Researchers look for ancient human remains in northern Greenland.

The strange history of the North American Arctic

Jia You is a news intern at Science

Archaeologists mapping ancient cultures in the North American Arctic—a region spanning present-day Greenland—have long puzzled over how different cultures relate to one another. Now, an unprecedented large-scale genomics study has traced many such cultures to the Paleo-Eskimos, a people who early inhabited the harsh environment continuously for 4000 years, only to vanish mysteriously about 700 years ago. The discovery could change how scientists understand migration patterns in the North American Arctic.

“This type of study … will be the key to solving many questions in history and prehistory,” says Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who was not involved with the research.

Archaeologists have found many distinct cultures in the New World Arctic’s past that belong to the Paleo-Eskimo tradition. First came the Saqqaqs, people who lived in tent camps and chased caribou and seals about 4000 years ago. Succeeding them were the Dorsets, walrus hunters whose culture went through three distinct phases 2800 years ago. Finally came the Thules, ancestors to modern Inuits, who sailed in large skin boats and hunted whales 1000 years ago.

What puzzled scientists was the relationship between these cultures. Did they belong to one people or distinct groups? Did they represent one migration into the Americas from the Old World, or multiple waves?

To answer these questions, biologist Maanasa Raghavan of the University of Copenhagen and her colleagues collected bone, teeth, and hair samples of 169 ancient humans from different time periods in the New World Arctic region. The team generated mitochondrial DNA and low-coverage whole genome data from these samples. They also sequenced genomes from present-day Inuits and Native Americans—the latter marked a first in research, as Native Americans often refuse DNA testing. The team obtained tribal permission with help from an indigenous woman.

After comparing the ancient and modern genetic data, the researchers found that the Saqqaq and Dorset cultures belonged to one Paleo-Eskimo people, whose genetic lineage continued in the region for more than 4000 years, from 3000 B.C.E. to 1300 C.E., contradicting previous theories that the diverse cultures came from different peoples.

The Paleo-Eskimos are genetically distinct from Native Americans and Inuits, which means they represent a separate, later pulse of migration into the New World, says evolutionary geneticist Eske Willerslev of the University of Copenhagen, a co-author of the study. This contradicts previous theories that humans arrived in the Americas in three waves, painting a scenario of four waves instead—the Amerinds, the Na Dene Native Americans, the Paleo-Eskimos, and the Neo-Eskimo Thules.

The discovery, reported online today in Science, gives researchers a better understanding of Paleo-Eskimos—a people who were close to nature and held on to traditional values—while raising more questions about them. For one, the study suggests that Paleo-Eskimos were a resilient people who survived Artic climate changes for thousands of years, including cold spells that depopulated most of the region. During those times, they likely took refuge in resource-abundant areas such as southern Canada, and spread out across the Arctic again during warmer times, Willerslev says.

Those residing in southern Canada would have shared the land with Native Americans for thousands of years, he says, yet genetic and archaeological evidence indicates no signs of mingling or intermarriage. “When we see people meeting each other, they may fight each other, but normally they also have sex with each other,” he says. “That does not seem to be the case here.”

In fact, genetic analysis shows that all Paleo-Eskimos shared the same mitochondrial DNA, which is passed from mothers to children. This unusual homogeneity suggests few women were among the early Paleo-Eskimo settlers, Willerslev says.

The finding is consistent with previous Y-chromosome analyses that suggest early Paleo-Eskimo settlers could have ranged from as few as 40 to 50 people closely related to one another, says anthropologist Theodore Schurr of the University of Pennsylvania, who was not involved with the research.

The tiny founder population might also explain why Paleo-Eskimos didn’t interact with other groups, but instead evolved diverse cultures on their own, Schurr says. Scientists suspect that even at the height of development, the Paleo-Eskimo population never exceeded 3000.

These reindeer hunters would have broken off into small pockets scattered across the New World Arctic, Schurr says. Each pocket may have adapted to local conditions and developed individual lifestyles in isolation.

What intrigues researchers most is why the Paleo-Eskimo lineage disappeared after the late Dorsets, around the same time that Neo-Eskimo Thules expanded rapidly to the Arctic. Archaeologists have found no evidence of violent conflict between the Thules and the Dorsets, but it would be hard to ignore contrasts between the two groups. The whale-hunting Thules lived in large, well-organized villages and boasted advanced technologies such as dog sleds and sinew-backed bows. The Dorsets, on the other hand, lived in small villages of 20 to 30 people and hunted with chipped stone blades.

The researchers suspect that the Dorsets might have been pushed out to the fringes of the Arctic, or perhaps annihilated by a disease. "It's just mind-blowing to imagine an entire people who just completely vanished,” Willerslev says.

Posted in Archaeology, Biology, Evolution