Geneticists have deciphered the prehistory of inhabitants of Kamchatka and North America

07. 06. 2019

A new and extensive study by 35 researchers from Europe, America and Russia sheds new light into the origin, genetic relations, and migrations of ancient Eskimos, Native Americans of the Na-Dene language family, and inhabitants of Kamchatka. The geneticists have used an arsenal of the newest genetics methods, they have obtained a large amount of genome data from human remains up to 2,000 years old, cooperated with archaeologists and a linguist, and created a new model of ancient settlement of this vast area. This unique study, led by Pavel Flegontov from the University of Ostrava and from the Biology Centre of the Czech Academy of Sciences, has now been published in the Nature journal.

Paleogenetics is a rapidly developing scientific discipline at the junction of archeology and genetics. Due to the rapid progress in the methods of sequencing DNA extracted from ancient bones, as well as in the methods of genetic data analysis, archaeogenetics is becoming an integral component of research in human prehistory. However, the study of relatively recent history (the last 5 thousand years) by methods of archaeogenetics is, oddly enough, methodologically difficult, despite the abundance of bone samples and their usually good preservation. As population density increased and means of transportation developed, mobility of people increased, as well. In the long millennia of the Paleolithic, genetic isolation of small groups of hunters was the dominant pattern, but later, from the beginning of the Neolithic, migration and population mixture became increasingly common.

An example of such a complex region is Chukotka and the American Arctic – the vast expanses of tundra and Arctic desert, inhabited by sparse groups of Chukchi, Eskimos, Aleuts, and Inuit. At first, the tundra zone of Alaska, the Canadian Arctic islands and Greenland was populated by so-called Paleo-Eskimos. This process began about 5,000 years ago with a migration of a small group of caribou, muskox and seal hunters across the Bering Strait. Then a succession of several archaeological cultures culminated in modern Eskimos, Aleuts, and Inuit. However, archeology very rarely can find whether the change in material culture was accompanied by mass migration and population replacement, or if these were primarily cultural processes. Therefore, for decades, there have been controversies about the history of the Arctic peoples, about the relationship of Paleo-Eskimos and Inuit, as well as about the interaction of Paleo-Eskimos and Native Americans who occupied the forests of Alaska and Canada adjacent to the tundra.

A cooperation between geneticists, archaeologists, and a linguist

An article recently published in the Nature journal is intended to put an end to a long-standing dispute about North American prehistory, i.e. about Paleo-Eskimos and speakers of the Na-Dene language family. This study resulted from a collaboration between three groups of geneticists: under the leadership of Pavel Flegontov (University of Ostrava, Czech Republic), Stefan Schiffels (Max Planck Institute in Jena, Germany), and David Reich (Harvard Medical School, Boston, USA), as well as other geneticists, archaeologists, and the linguist Edward Vajda.

Since 2010, when paleogenetics appeared on the scene, opinions of various scientific teams regarding genetic relations, migration waves, and mixing of the Paleo-Eskimos, Native Americans speaking the Na-Dene languages, and inhabitants of Kamchatka and Chukotka on the Asian side have been contradictory. According to Flegontov, these disagreements have been caused by several factors.

“There were several migration waves of Asian genes to the North American continent that differ relatively little genetically; and second, there may have been multiple migrations of these groups back and forth across the Bering Strait and the concomitant population mixing. Under such conditions, standard methods of paleogenetic analysis tend to give unreliable results,” explains Pavel Flegontov.

The scientists analysed samples of both ancient and modern populations

To overcome this problem, Flegontov and co-authors collected a wide arsenal of methods, both standard and novel, and also for the first time obtained new samples of ancient genomes. “These were 11 Aleuts from 280 to 2050 years ago, 3 Athabaskans from 710 years ago, 23 ancient Eskimos of Chukotka from 620 to 1770 years ago, and also 8 individuals of the Baikal region and one Paleo-Eskimo dated to about 1760 years ago,” says Pavel Flegontov. The article also presents genetic data for modern populations: Inuit from Alaska, Kets, Nganasans, Enets, and Selkups from West Siberia (93 individuals in total). Breakthrough results were obtained using two independent graph methods. The two most likely branching orders were tested on a set of 133 thousand population combinations.

Crossing the Bering Strait more than 5,000 years ago

The study shows that more than 5,000 years ago, Paleo-Eskimo and Chukotko-Kamchatkan populations were separated due to the migration of the former across the Bering Strait to North America (see Figure A – the red arrow). About 4800 years ago, i.e. soon after the migration, Paleo-Eskimos mixed with two groups of “First Americans”. One of these admixture events (30–40% of Paleo-Eskimo ancestry) gave rise to the peoples of the Na-Dene language family. Another (about 50% of Paleo-Eskimo admixture) gave rise to the peoples of the Eskimo-Aleut language family. It is noteworthy that Paleo-Eskimo ancestry was found in all branches of the Na-Dene family, and its level is noticeably lower among neighboring peoples of other language families. Although the genetic results do not allow an unambiguous conclusion about the original homeland of the Na-Dene family (in America or Siberia), we can assume that Paleo-Eskimos mixed with an American population that was a common ancestor of all the Na-Dene peoples.

Migration to Aleutian Islands and expansion to Alaska

As for the history of Eskimos and Aleuts, the mixture of Amerindians and Paleo-Eskimos dates back to 4,900–4,400 years ago (Figure B – blue arrows). Although we do not have samples of this age from Alaska, combining genetic and archaeological results, we can assume that this event played a key role in the ethnogenesis of the Eskimo-Aleut speakers and occurred in southern Alaska: in the Kodiak Archipelago and the Alaska Peninsula. It was there that the earliest communities relying almost entirely on marine resources were found, as well as some features of material culture typical of the later Eskimos and Aleuts (indicated by a brown oval in the figure). Shortly after mixing with Amerindians, the Aleut ancestors probably migrated to the Aleutian Islands (the thin blue arrow pointing down) and then remained in relative isolation, which well explains the absence of Chukotko-Kamchatkan admixture among Aleuts. The other group probably migrated north towards the Bering Strait and then for some reason returned to Chukotka (the thin blue arrows), where about 2,200 years ago communities having typical Eskimo-Inuit traits emerged. About 2,000 years ago, a two-way mixture of Eskimos and ancestors of the Chukchi and Koryaks occurred (the purple arrows in the figure). Mastering whale hunting led to a dramatic population growth and expansion of Inuit to Alaska approximately 1,150 years ago. Then the Inuit spread throughout the American Arctic and ousted Paleo-Eskimos (the thick blue arrow).

On the opening image: More than 5,000 years ago, Paleo-Eskimo and Chukotko-Kamchatkan populations were separated due to the migration of the former across the Bering Strait to North America (see Figure A – the red arrow). As for the history of Eskimos and Aleuts, the mixture of Amerindians and Paleo-Eskimos dates back to 4,900–4,400 years ago (Figure B – blue arrows).

Prepared by: Daniela Procházková, Biology Centre of the CAS, in cooperation with the Department of Media Communication of the Head Office of the CAS
Illustration: Biology Centre of the CAS