Beringian Standstill Hypothesis - Land of the First Americans

Were the Original Colonists of the Americas Beringians?

Map of Revised Beringia Timing (Raghavan et al. 2015)
This image shows origins and population history of Native Americans, based on the research by Raghavan et al. Raghavan et al., Science (2015)

The Beringian Standstill Hypothesis, also known as the Beringian Incubation Model (BIM), proposes that the people who would eventually colonize the Americas spent between ten to twenty thousand years stranded on the Bering Land Bridge (BLB), the now-submerged plain beneath the Bering Sea called Beringia.

The BIM argues that during the turbulent times of the Last Glacial Maximum about 30,000 years ago, people from what is today Siberia in northeastern Asia arrived in Beringia.

Because of local climate changes, they became trapped there, cut off from Siberia by glaciers in the Verkhoyansk Range in Siberia and in the Mackenzie River valley in Alaska. There they remained in the tundra environment of Beringia until retreating glaciers and rising sea levels allowed--and eventually forced--their migration into the remainder of the Americas about 15,000 years ago. If true, the BIM explains the long-recognized, deeply puzzling discrepancy of the late dates for the colonization of the Americas (Preclovis sites such as Upward Sun River Mouth in Alaska) and the similarly stubbornly early dates of the antecedent Siberian sites (the Yana Rhinoceros Horn site in Siberia; for some of this discussion, see O'Rourke and Raff).

The BIM also disputes the notions of "three waves" of migration. Up until recently, scholars explained a perceived variation in mitochondrial DNA among modern (indigenous) Americans by postulating multiple waves of migration from Siberia, or even, for a while, Europe.

But, recent macro-studies of mtDNA identified a series of pan-American genome profiles, shared by modern Americans from both continents, decreasing the perception of widely varying DNA. Scholars still think that there was a post-glacial migration from northeast Asia of the ancestors of the Aleut and Inuit--but that side-issue is not addressed here, see Adachi and colleagues, Long and colleagues, and Schurr and colleagues in the bibliography.

Evolution of the Beringian Standstill Hypothesis

The environmental aspects of the BIM were proposed by Eric Hultén in the 1930s, who argued that the now-submerged plain beneath the Bering Strait was a refuge for people, animals and plants during the coldest parts of the Last Glacial Maximum, between 28,000 and 18,000 calendar years ago (cal BP). Dated pollen studies from the floor of the Bering Sea and from adjacent lands to the east and west support Hultén's hypothesis, indicating that the region was a mesic tundra habitat, similar to that of tundra in the foothills of the Alaska range today. Several tree species, including spruce, birch and alder, were present in the region, providing fuel for fires.

Mitochondrial DNA is the strongest support for the BIM hypothesis. That was published in 2007 by Tamm and colleagues, who identified evidence for the genetic isolation of ancestral Native Americans from Asia. Tamm and colleagues identified a set of genetic haplogroups common to most living Native American groups (A2, B2, C1b, C1c, C1d*, C1d1, D1, and D4h3a), haplogroups that had to have arisen after their ancestors left Asia, but before they dispersed into the Americas.

In a 2012 study, Auerbach reports that although there is variation among the five (admittedly a very tiny population) early Holocene male skeletons which have been recovered from North America, the individuals all have wide bodies, a trait shared by Native American communities today and which is associated with adaptations to cold climates.

Auerbach argues that people from the Americas have wider bodies than other populations around the world. If true, that also supports the isolation model, as it would have been a shared trait developed in Beringea before people dispersed.

Genomes and Beringia

A 2015 study (Raghavan et al.) comparing genomes of modern people from all over the world found support for the Beringian Standstill Hypothesis, albeit reconfiguring the time depth. This study argues that the ancestors of all Native Americans were genetically isolated from East Asians no earlier than than 23,000 years ago. They hypothesize that a single migration into the Americas occurred between 14,000 and 16,000 years ago, following the open routes within the interior "Ice Free" corridors or along the Pacific coast.

By the Clovis period (~12,600-14,000 years ago), isolation caused a split among the Americans into 'northern'--Athabascans and northern Amerindian groups--and 'southern'--communities from southern North America and Central and South America.

Raghavan et al. also found what they termed a "distant Old World signal" related to Australo-Melanesians and East Asians in some Native American groups, ranging from a strong signal in the Suruí of Brazil's Amazon forest to a much weaker signal in northern Amerindians such as Ojibwa. Raghavan et al. hypothesize that the Australo-Melanesian gene flow may have arrived from Aleutian Islanders traveling along the Pacific rim about 9,000 years ago.

In an article released the same week as Raghavan et al., Skoglund et al. reported similar research and resulting genetic evidence. While their results are largely the same, they emphasized the Australo-Melanesian gene flow among South American groups, terming it evidence of "Population Y", and arguing that the data support a long-standing theory concerning ancient Australo-Melanesian voyages to the New World. This model is over a decade old, but was built on cranial morphology and has not had genome support before this time. Skoglund et al. admit that DNA has not been retrieved from crania exhibiting the supposed physical affinities to Australo-Melanesians.

Archaeological Sites

  • Yana Rhinoceros Horn Site, Russia, 28,000 cal BP, six sites above the Arctic Circle and east of the Verkhoyansk Range.
  • Mal'ta, Russia, 15,000-24,000 cal BP: DNA of a child burial at this upper Paleolithic site shares genomes with modern western Eurasians and Native Americans both
  • Funadomari, Japan, 22,000 cal BP: Jomon culture burials share mtDNA in common with Eskimo (haplogroup D1, see Adachi)

Sources

This article is a part of the About.com guide to the Population of Americas, and the Dictionary of Archaeology.

Adachi N, Shinoda K-i, Umetsu K, and Matsumura H. 2009. Mitochondrial DNA analysis of Jomon skeletons from the Funadomari site, Hokkaido, and its implication for the origins of Native American. American Journal of Physical Anthropology 138(3):255-265. doi:10.1002/ajpa.20923

Auerbach BM. 2012. Skeletal variation among early Holocene North American humans: Implications for origins and diversity in the Americas.

American Journal of Physical Anthropology 149(4):525-536. doi: 10.1002/ajpa.22154

Hoffecker JF, Elias SA, and O'Rourke DH. 2014. Out of Beringia? Science 343:979-980. doi:10.1126/science.1250768

Kashani BH, Perego UA, Olivieri A, Angerhofer N, Gandini F, Carossa V, Lancioni H, Semino O, Woodward SR, Achilli A et al.

2012. Mitochondrial haplogroup C4c: A rare lineage entering America through the ice-free corridor? American Journal of Physical Anthropology 147(1):35-39. doi:10.1002/ajpa.21614

Long JC, and Cátira Bortolini M. 2011. New developments in the origins and evolution of Native American populations. American Journal of Physical Anthropology 146(4):491-494. doi:10.1002/ajpa.21620

O'Rourke DH, and Raff JA. 2010. The Human Genetic History of the Americas: The Final Frontier.> Current Biology 20(4):R202-R207. doi:10.1016/j.cub.2009.11.051

Perego UA, Achilli A, Angerhofer N, Accetturo M, Pala M, Olivieri A, Kashani BH, Ritchie KH, Scozzari R, Kong Q-P et al. 2009. Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups. Current Biology 19:1–8. doi: 10.1016/j.cub.2008.11.058

Raff JA, Bolnick DA, Tackney J, and O'Rourke DH. 2011. Ancient DNA perspectives on American colonization and population history. American Journal of Physical Anthropology 146(4):503-514. doi: 10.1002/ajpa.21594

Raghavan M, Skoglund P, Graf KE, Metspalu M, Albrechtsen A, Moltke I, Rasmussen S, Reedik M, Campos PF, Balanovska E et al. 2014. Upper Palaeolithic Siberian genome reveals dual ancestry of Native Americans.

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Raghavan M, Steinrücken M, Harris K, Schiffels S, Rasmussen S, DeGiorgio M, Albrechtsen A, Valdiosera C, Ávila-Arcos MC, Malaspinas A-S et al. 2015. Genomic evidence for the Pleistocene and recent population history of Native Americans. Science. doi: 10.1126/science.aab3884

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Skoglund P, Mallick S, Bortolini MC, Chennagiri N, Hunemeier T, Petzl-Erler ML, Salzano FM, Patterson N, and Reich D. 2015. Genetic evidence for two founding populations of the Americas. Nature advance online publication. doi: 10.1038/nature14895

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