Beringian Standstill Hypothesis of the First Americans

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. Key Takeaways: Beringian Standstill The Beringian Standstill Hypothesis (or Beringian Incubation Model, BIM) is a widely-supported model of the human colonization of the Americas.  The theory suggests that the original colonizers of the Americas were Asians, who were isolated by climate change on the now-underwater island of Beringea for several thousand years.  They left Beringea after melting glaciers permitted movement east- and south-ward, about 15,000 years ago.  Originally proposed in the 1930s, the BIM has since been supported by genetic, archaeological, and physical evidence.   Processes of the Beringian Standstill 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 beginning 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, such as the Yana Rhinoceros Horn site in Siberia. 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. Evolution of the Beringian Standstill Hypothesis The environmental aspects of the BIM were proposed by Eric Hultà ©n 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 Hultà ©ns 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 Estonian geneticist Erika 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. Suggested physical traits supporting the isolation of the Beringians are comparatively wide bodies, a trait shared by Native American communities today and which is associated with adaptations to cold climates; and a dental configuration which researchers G. Richard Scott and colleagues call super-Sinodont. Genomes and Beringia A 2015 study by geneticist Maanasa Raghavan and colleagues compared genomes of modern people from all over the world and 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 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 and colleagues 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 Suruà ­Ã‚  of Brazils Amazon forest to a much weaker signal in northern Amerindians such as Ojibwa. The group hypothesizes that the Australo-Melanesian gene flow may have arrived from Aleutian Islanders traveling along the Pacific rim about 9,000 years ago. More recent studies (such as that of Brazilian geneticist Thomaz Pinotti 2019) continue to support this scenario. Archaeological Sites Yana Rhinoceros Horn Site, Russia, 28,000 cal BP, six sites above the Arctic Circle and east of the Verkhoyansk Range.Malta, 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 bothFunadomari, Japan, 22,000 cal BP: Jomon culture burials share mtDNA in common with Eskimo (haplogroup D1)Blue Fish Caves, Yukon Territory, Canada, 19,650 cal BPOn Your Knees Cave, Alaska, 10,300 cal BP Paisley Caves, Oregon 14,000 cal BP, coprolites containing mtDNAMonte Verde, Chile, 15,000 cal BP, first confirmed preclovis site in the AmericasUpward Sun River, Alaska, 11,500 ka.Kennewick  and Spirit Cave, USA, both 9,000 years cal BP Charlie Lake Cave, British Columbia, CanadaDaisy Cave, California, USAyer Pond, Washington, USUpward Sun River Mouth, Alaska, US Selected Sources Bourgeon, Lauriane, Ariane Burke, and Thomas Higham. Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada. PLoS ONE 12.1 (2017): e0169486. Print.Moreno-Mayar, J. Và ­ctor, et al. Terminal Pleistocene Alaskan Genome Reveals First Founding Population of Native Americans. Nature 553 (2018): 203–08. Print.Pinotti, Thomaz, et al. Y Chromosome Sequences Reveal a Short Beringian Standstill, Rapid Expansion, and Early Population Structure of Native American Founders. Current Biology 29.1 (2019): 149-57.e3. Print.Raghavan, Maanasa, et al. Genomic Evidence for the Pleistocene and Recent Population History of Native Americans. Science 349.6250 (2015). Print.Scott, G. Richard, et al. Sinodonty, Sundadonty, and the Beringian Standstill Model: Issues of Timing and Migrations into the New World. Quaternary International 466 (2018): 233–46. Print.Tamm, Erika, et al. Beringian Standstill and Spread of Native Ameri can Founders. PLoS ONE 2.9 (2007): e829. Print.Vachula, Richard S., et al. Evidence of Ice Age Humans in Eastern Beringia Suggests Early Migration to North America. Quaternary Science Reviews 205 (2019): 35–44. Print.Wei, Lan-Hai, et al. Paternal Origin of Paleo-Indians in Siberia: Insights from Y-Chromosome Sequences. European Journal of Human Genetics 26.11 (2018): 1687–96. Print.