Paleo-Eskimos were independent of Inuit and Native American expansions
In the 1980s, the American linguist Joseph Greenberg proposed that Native American languages could be classified within three families: Eskimo-Aleut, Na Dene and Amerind. He further suggested that each family corresponded to a separate migration into the New World from Siberia and concluded, therefore, that the New World had been peopled by three migrations. Greenberg’s views remained controversial for many years as most mitochondrial and Y-chromosomal genetic studies indicated that there had been no more than two migrations. In 2012, however, he was apparently vindicated when David Reich and his colleagues presented a high resolution study of 52 Native American and 17 Siberian groups genotyped at 364,470 single nucleotide polymorphisms. The results indicated that there had indeed been three migrations broadly corresponding to the three language families: specifically (i) First Americans, (ii) Eskimo-Aleuts and, (iii) Saqqaq and Na Dene speakers.
These results are built on by a major new study conducted by an international team numbering over fifty researchers led by geneticist Maanasa Raghavan from the University of Copenhagen. The study focussed on mitochondrial and genome-wide sequences obtained from ancient bone, hair and teeth samples of Arctic Siberia, Alaska, Canada, and Greenland, and high-coverage genomes of two present-day Greenlandic Inuit, two Siberian Nivkhs, one Aleutian Islander, and two Athabascan Native Americans.
From this data, researchers hoped to resolve issues regarding the complex archaeological record of the Early Paleo-Eskimos (Pre-Dorset/Saqqaq), the Late Paleo-Eskimos (Early Dorset, Middle Dorset, and Late Dorset), and the Thule cultures. They were able to show that the Paleo-Eskimos reached the New World in a single migration from Siberia around 3000 BC and displayed genetic continuity for more 4,000 years. About 700 years ago they were replaced by the Thule people, who were the ancestors of the present day Inuit.
While supporting Reich et al overall, the results indicated that the Saqqaq tradition and Na Dene speakers were not part of the same migratory wave: accordingly the Paleo-Eskimos must have arrived in a separate migration to the three waves identified by Reich et al, implying that the New World was populated by four migrations in all.
1. Reich, D. et al., Reconstructing Native American population history. Nature 488, 370–374 (2012).
2. Greenberg, J., Turner, C. & Zegura, S., The Settlement of the Americas: A Comparison of the Linguistic, Dental, and Genetic Evidence. Current Anthropology 27 (5), 477-497 (1986).
3. Raghavan, M. et al., The genetic prehistory of the New World Arctic. Science 345 (620), 1020,1255832 (2014).