A new paper reports on a comprehensive DNA study of current and former inhabitants of Greenland, Arctic Canada, Alaska, the Aleutian Islands and Siberia.
M Raghavan et al, The genetic prehistory of the New World Arctic. Science, 2014; 345 (6200): 1255832 DOI:10.1126/science.1255832
In this study, researchers show that the people who lived in the Arctic from about 5,000 years ago until about 700 years ago, represented a distinct wave of migration, separate from both Native Americans – who crossed the Bering Strait much earlier – and the Inuit, who came from Siberia to the Arctic several thousand years after the Palaeo-population.
“Our genetic studies show that, in reality, the Palaeo-population – representing one single group – were the first people in the Arctic, and they survived without outside contact for over 4,000 years,” says Lundbeck Foundation Professor Eske Willerslev from Centre for GeoGenetics at the Natural History Museum, University of Copenhagen, who headed the study.
“Our study also shows that the Palaeo-population, after surviving in near-isolation in the harsh Arctic environment for more than 4,000 years, disappeared around 700 years ago – about the same time when the ancestors of modern-day Inuit spread eastward from Alaska,” adds Dr. Maanasa Raghavan of Centre for GeoGenetics and lead author of the article.
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.
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
All Paleo-Eskimos represent a single migration pulse from Siberia into the Americas, independent of the Neo-Eskimo Thule people (ancestors of modern-day Inuit) and the related extinct Sadlermiut population. The Siberian Birnirk people were likely cultural and genetic ancestors of modern-day Inuit. We also show ancient admixture between the Paleo- and Neo-Eskimo lineages, occurring at least 4000 years ago.
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.
It has now become apparent that even at glacial maximum when the ice sheets blanketed much of North America and Greenland, humans lived in the Arctic wastes of Siberia and also that they could move across the land bridge which is now the Bering Straits. For long periods of time – perhaps 500 generations – they may have been isolated in Beringia.
The now submerged land bridge (Beringia) between Asia and North America was not just a little strip of land across which the ancestors of native Americans quickly moved across. It was not just a rest stop for the journey to America. The “bridge” was a vast area of land and itself served as a fairly permanent habitat and refuge for ancient humans for around 10,000 years (500 generations) from 25,000 to 15,000 years ago. Beringia extended some 1,600 km from north to south and almost 5,000 km east to west from Siberia’s Verkoyansk Range to the Mackenzie River in Canada. It could well have been the increasing sea levels as the world came out of a glacial period into the current inter-glacial and a shrinking Beringia which led to the migrations from Beringia into North America.
Even during glacial maximum and as the ice sheets retreated, North America was covered by two large ice sheets but it may well have been possible at some times, for some hardy migrants from Beringia, to travel through Alaska and then south through the gaps between the Cordilleran and the Laurentide ice sheets. This image is an estimate for about 13k years ago.