Image copyright Carsten Egevang Image caption The ancestors of modern-day Inuit made sharp tools mainly by grinding slate, in contrast to the flaked stones used by Paleo-Eskimos

A new "genetic prehistory" provides the best picture ever assembled of how the North American Arctic was populated, from 6,000 years ago to the present.

DNA sequences from living and ancient inhabitants show a single influx from Siberia produced all the "Paleo-Eskimo" cultures, which died out 700 years ago.

Modern-day Inuit and Native Americans arose from separate migrations.

Previously our understanding of this history was based largely on cultural artefacts, dug up by archaeologists.

The study, which has more than 50 authors hailing from institutions across the globe, was published in the journal Science.

A single founding population settled, and endured the harsh conditions of the Arctic, for almost 5,000 years Dr Maanasa Raghavan, Natural History Museum of Denmark

Multiple models

Researchers of North American prehistory have long disagreed about the lineages of Arctic peoples, ranging from the first arrivals who mostly hunted ox and reindeer, through at least four other cultural groupings, to the modern Inuit and their marine hunting culture.

"Since the 1920s or so, it has been heavily discussed what is the relationship between these cultural groups," said senior author Prof Eske Willerslev from the Natural History Museum of Denmark, which is part of the University of Copenhagen.

"All kinds of hypotheses have been proposed. Everything from complete continuity between the first people in the Arctic to present-day Inuits, [while] other researchers have argued that the Saqqaq and the Dorset and the Thule are distinct people."

These three broadly-grouped cultures all occupied the north of North America: the Saqqaq until 2,500 years ago, followed by a series of Dorset cultures and then the Thule (Inuit ancestors) from about 1,000 years ago.

Image copyright Claus Andreasen Image caption The study included ancient remains collected from across the North American Arctic, including Greenland

Using DNA from more than 150 ancient human remains, the researchers showed that all the Saqqaq and Dorset peoples, further bundled together as Paleo-Eskimos, represent a single genetic lineage. They all stem from a migration across the Bering Strait from Siberia that began some 6,000 years ago.

"A single founding population settled, and endured the harsh environmental conditions of the Arctic, for almost 5,000 years - during which time the culture and lifestyle changed enough to be represented as distinct cultural units," explained Dr Maanasa Raghavan, first author of the new paper.

Four waves of arrivals Paleo-Eskimos (beginning around 6,000 years ago) including Saqqaq and three separate Dorset cultures

Thule people (beginning around 1,000 years ago), ancestors of the modern-day Inuit

Two waves further south, giving rise to different groups of Native American ancestors

She explained that this was unusual in the study of ancient people, and suggested that cultural changes, identified through tools and other remains, are not the best way to gauge ancient population movements.

History of violence?

The findings also confirm that before the Paleo-Eskimo culture suddenly disappeared around 700 years ago, there was no mixing between those communities and the Inuit ancestors, who arose from a second, distinct Siberian migration.

Carbon dating suggests they may have overlapped in Greenland and northern Canada for up to several centuries, but cultural remains do not betray any interaction: the Paleo-Eskimos continued to use flaked stone tools, for example, while the Thule used ground slate.

The lack of any genetic cross-over may indicate that the previous inhabitants died out before the Thule arrived; it also "raises the question", according to Prof William Fitzhugh, another author of the study, of a possible "prehistoric genocide".

Image copyright University of Aberdeen/Qanirtuuq, Inc Image caption Previously, most theories about these historical populations were based on cultural artefacts, like these ceremonial dolls made by Bering Sea Eskimos

Prof Fitzhugh, from the Smithsonian Institute in Washington DC, said the disappearance of the Paleo-Eskimos - "within the space of 100 or 150 years, a whole population, a whole cultural tradition" - was something of a mystery.

And yet Inuit legend suggests only friendly relations between their Thule ancestors and the "gentle giants" who preceded them.

Prof Fitzhugh emphasised he was only speculating: "We don't have any good evidence that there was hostility between the Dorset people and the Thule people."

There is much more to figure out, he said, describing the new work as "an opening chapter in the genetic history of the New World Arctic".

Overall, the findings add a "fourth wave" to existing models of Arctic settlement in the New World, by confirming that all the Paleo-Eskimos arose from a distinct, early migration.

After comparing ancient samples with genomes from living people, the researchers concluded that subsequent, separate waves gave rise to the Thule people (and their descendents the Inuit), as well as two distinct groups of Native Americans further south.

This contrasts with an earlier genetic study, which suggested the earliest known Arctic culture, the Saqqaq, arose from one of the two waves Native American ancestral arrivals.