© Carsten Egevang
A view of the world that modern-day Canadian Inuits inhabit. A study published Thursday effectively ruled out a theory that the DNA of the Dorset people lives on in modern Inuits.
Seven hundred years ago, the Dorset people disappeared from the Arctic. The last of the Paleo-Eskimos, the Dorset had dominated eastern Canada and Greenland for centuries, hunting seal and walrus through holes in the ice and practicing shamanistic rituals with ornate carvings and masks.

Then, they promptly ceased to exist. Modern archaeologists have scoured troves of Arctic artifacts, searching for clues to the Dorset's sudden extinction. Did they assimilate when the Thule, ancestors of the modern Inuit, advanced from the Bering Strait with dog sleds, harpoons and large skin boats? Or did they die out, victims of either an unfortunate epidemic or a violent prehistoric genocide?

Now, scientists have begun to chip away at this and other mysteries of the New World Arctic. In a paper published Thursday in the journal Science, researchers analyzed 169 ancient DNA samples to study the origins and migration patterns of early Arctic cultures. The results point to a single, genetically distinct Paleo-Eskimo population that thrived in isolation for more than 4,000 years, only to vanish in a matter of decades.

"By using genetics and genomics, they were able to answer questions that archaeologists have been trying to solve for decades," said Todd R. Disotell, a professor of anthropology at New York University, who was not involved in the research. "Tiny fragments of teeth and hair are now yielding more data than we ever imagined."

Archaeologists traditionally rely on ancient artifacts, like spearheads and potsherds, or linguistics to track population shifts. When ancient cultures start using modern tools or altering their languages, researchers consider such changes cultural and even biological turning points, representing an inevitable period of intermarriage and assimilation.

Radiocarbon dating of human remains can be inexact. The Paleo-Eskimos subsisted on seafood, and the Arctic is packed with ancient carbon that is absorbed by marine life and may confound efforts to date cultural changes.

But genomic analysis offers a far more direct link to the past. "With genetics, you're looking at the ancient people themselves, not their refuse, so to speak," Dr. Disotell said.

To learn more about the Paleo-Eskimos and their sudden disappearance from the historical record, researchers collected DNA fragments from ancient human remains across Greenland, Canada and Siberia. Their results suggest that the Paleo-Eskimos remained genetically isolated for thousands of years, and that the Dorset culture did not vanish through assimilation. Modern Inuits, then, are descendants of the Thule and not directly related to the Paleo-Eskimos.

"This is surprising, because every time people meet each other we find evidence of sex between the people," said Eske Willerslev, an evolutionary biologist at the Center for GeoGenetics at the University of Copenhagen and an author of the study. "But here we have a unique situation, where even though we know they must have been in touch with their neighbors, they chose to live in isolation."

If it was not assimilation, what happened to the Dorset? The study suggests that Paleo-Eskimos arrived in the New World in a single migration, rather than in waves, as previously thought. Analysis of mitochondrial DNA, which allows researchers to pinpoint matrilineal ancestry, suggests rampant inbreeding among the isolated Dorset people, a factor that may have weakened their population and ultimately contributed to their demise.

"Certainly they survived for almost 5,000 years, so they weren't completely destroyed by inbreeding," Dr. Willerslev said. "But it causes a number of medical problems, and I wouldn't be surprised if that had an effect on them."

Another possibility, Dr. Disotell explained, is that the Dorset braved generations of harsh tundra conditions only to succumb to the effects of climate change. In the Arctic, even minor shifts in temperature can devastate marine life, cutting off vital food sources. The archaeological record, in fact, suggests that several such events had nearly wiped out the Paleo-Eskimos before.

"When you're dealing with sea ice, just a few degrees can be transformative," Dr. Disotell said. "Three bad winters in a row where you can't hunt seals, and you're in trouble."

Although the study effectively ruled out the theory that Dorset DNA lives on in the modern Inuit, the mystery of the last Paleo-Eskimos remains unsolved. For Dr. Willerslev and his team, the next step will be to examine even more ancient human remains, in search of clues.

"We're trying to get our hands on more ancient human skeletons on both sides of the Bering Strait," he said. "I wouldn't be surprised if we find evidence of a new migration that we weren't aware of."

The current data, however, tells a fascinating story unto itself. An ancient culture managed to survive in one of the most extreme environments on Earth, an uninterrupted bloodline that spanned thousands of years, only to disappear without a trace.

"This might be a good lesson for us today," Dr. Disotell said. "Long-term stability still means you can disappear. After 4,300 years, bam, you're gone in decades."