Until recently, the settlement of the Americas seemed largely divorced from the out-of-Africa dispersal of anatomically modern humans, which began at least 50,000 years ago. Native Americans were ...thought to represent a small subset of the Eurasian population that migrated to the Western Hemisphere less than 15,000 years ago. Archeological discoveries since 2000 reveal, however, that Homo sapiens occupied the high-latitude region between Northeast Asia and northwest North America (that is, Beringia) before 30,000 years ago and the Last Glacial Maximum (LGM). The settlement of Beringia now appears to have been part of modern human dispersal in northern Eurasia. A 2007 model, the Beringian Standstill Hypothesis, which is based on analysis of mitochondrial DNA (mtDNA) in living people, derives Native Americans from a population that occupied Beringia during the LGM. The model suggests a parallel between ancestral Native Americans and modern human populations that retreated to refugia in other parts of the world during the arid LGM. It is supported by evidence of comparatively mild climates and rich biota in south-central Beringia at this time (30,000-15,000 years ago). These and other developments suggest that the settlement of the Americas may be integrated with the global dispersal of modern humans.
Out of Beringia? Hoffecker, John F.; Elias, Scott A.; O'Rourke, Dennis H.
Science (American Association for the Advancement of Science),
02/2014, Letnik:
343, Številka:
6174
Journal Article
Recenzirano
A shrub tundra refugium on the Bering land bridge may have played a pivotal role in the peopling of the Americas.
Based on the distribution of tundra plants around the Bering Strait region, Eric ...Hultén proposed in the 1930s that the now-submerged plain between Chukotka and Alaska—the Bering land bridge—became a refugium for shrub tundra vegetation during cold periods (
1
), which include the last glacial maximum (LGM) between ∼28,000 and 18,000 cal BP (calibrated radiocarbon years before the present). Adjoining areas to the west and east supported drier plant communities with a higher percentage of grasses during glacial periods. According to Hultén, when warmer and wetter conditions returned to these areas, the land bridge, which he named Beringia, became a center of dispersal for tundra plants. Now it appears that it also may have been a glacial refugium and postglacial center of dispersal for the people who first settled the Americas.
Because of the ubiquitous adaptability of our material culture, some human populations have occupied extreme environments that intensified selection on existing genomic variation. By 32,000 years ...ago, people were living in Arctic Beringia, and during the Last Glacial Maximum (LGM; 28,000–18,000 y ago), they likely persisted in the Beringian refugium. Such high latitudes provide only very low levels of UV radiation, and can thereby lead to dangerously low levels of biosynthesized vitamin D. The physiological effects of vitamin D deficiency range from reduced dietary absorption of calcium to a compromised immune system and modified adipose tissue function. The ectodysplasin A receptor (EDAR) gene has a range of pleiotropic effects, including sweat gland density, incisor shoveling, and mammary gland ductal branching. The frequency of the human-specific EDAR V370A allele appears to be uniquely elevated in North and East Asian and New World populations due to a bout of positive selection likely to have occurred circa 20,000 y ago. The dental pleiotropic effects of this allele suggest an even higher occurrence among indigenous people in the Western Hemisphere before European colonization. We hypothesize that selection on EDAR V370A occurred in the Beringian refugium because it increases mammary ductal branching, and thereby may amplify the transfer of critical nutrients in vitamin D-deficient conditions to infants via mothers’ milk. This hypothesized selective context for EDAR V370A was likely intertwined with selection on the fatty acid desaturase (FADS) gene cluster because it is known to modulate lipid profiles transmitted to milk from a vitamin D-rich diet high in omega-3 fatty acids.
The Bering Land Bridge (BLB) connected the two principal arctic biological refugia, Western and Eastern Beringia, during intervals of lowered sea level in the Pleistocene. Fossil evidence from ...lowland BLB organic deposits dating to the Last Glaciation indicates that this broad region was dominated by shrub tundra vegetation, and had a mesic climate. The dominant ecosystem in Western Beringia and the interior regions of Eastern Beringia was steppe–tundra, with herbaceous plant communities and arid climate. Although Western and Eastern Beringia shared many species in common during the Late Pleistocene, there were a number of species that were restricted to only one side of the BLB. Among the vertebrate fauna, the woolly rhinoceros was found only to the west of the BLB, North American camels, bonnet-horned musk-oxen and some horse species were found only to the east of the land bridge. These were all steppe–tundra inhabitants, adapted to grazing. The same phenomenon can be seen in the insect faunas of the Western and Eastern Beringia. The steppe–tundra beetle fauna of Western Beringia was dominated by weevils of the genus
Stephanocleonus, a group that was virtually absent from Eastern Beringia. The dry-adapted weevils,
Lepidophorus lineaticollis and
Vitavitus thulius were important members of steppe–tundra communities in Eastern Beringia, but were either absent or rare in Western Beringia. The leaf beetles
Chrysolina arctica,
C. brunnicornis bermani, and
Galeruca interrupta circumdata were typical members of the Pleistocene steppe–tundra communities of Western Beringia, but absent from Eastern Beringia. On the other hand, some steppe tundra-adapted leaf beetles managed to occupy both sides of the BLB, such as
Phaedon armoraciae. Much of the BLB remains unstudied, but on biogeographic grounds, it appears that there was some kind of biological filter that blocked the movements of some steppe–tundra plants and animals across the BLB.
Beringia and the peopling of the Western Hemisphere Hoffecker, John F; Elias, Scott A; Scott, G Richard ...
Proceedings of the Royal Society. B, Biological sciences,
01/2023, Letnik:
290, Številka:
1990
Journal Article
Recenzirano
Odprti dostop
Did Beringian environments represent an
to humans until less than 15 000 years ago or was access to the Americas controlled by the spatial-temporal distribution of North American ice sheets? ...Beringian environments varied with respect to climate and biota, especially in the two major areas of exposed continental shelf. The East Siberian Arctic Shelf ('Great Arctic Plain' (GAP)) supported a dry steppe-tundra biome inhabited by a diverse large-mammal community, while the southern Bering-Chukchi Platform ('Bering Land Bridge' (BLB)) supported mesic tundra and probably a lower large-mammal biomass. A human population with west Eurasian roots occupied the GAP before the Last Glacial Maximum (LGM) and may have accessed mid-latitude North America via an interior ice-free corridor. Re-opening of the corridor less than 14 000 years ago indicates that the primary ancestors of living First Peoples, who already had spread widely in the Americas at this time, probably dispersed from the NW Pacific coast. A genetic 'arctic signal' in non-arctic First Peoples suggests that their parent population inhabited the GAP during the LGM, before their split from the former. We infer a shift from GAP terrestrial to a subarctic maritime economy on the southern BLB coast before dispersal in the Americas from the NW Pacific coast.
AIM: To use a variety of data sources to infer how northern boreal trees recovered their range upon deglaciation and/or Holocene warming. LOCATION: Scandinavia, Alaska/north‐west Canada (eastern ...Beringia). METHODS: Mapped fossil occurrences for Picea (spruce) were assessed against available palaeoenvironmental and phylogeographic information. RESULTS: For Scandinavia, Last Glacial Maximum (LGM) evidence of Picea is confined to one DNA record, but late‐glacial and early‐Holocene records include scattered macrofossils. Holocene pollen data show a clear east–west increase to high values. A haplotype unique to the Scandinavian Peninsula is recognized. For eastern Beringia pre‐ and post‐LGM macrofossils occur, but the LGM fossil record comprises only scattered low pollen values. Early Holocene pollen values increase markedly c. 11 cal yr bp (north‐west Canada) and c. 10 kcal yr bp (central Alaska). Also at this time three sites on the Bering Land Bridge indicate the presence of Picea where it is now absent. Several unique regional haplotypes were recorded; while most are rare one is common in some modern populations. MAIN CONCLUSIONS: Small Picea populations probably occurred in pre‐Holocene Scandinavia, but pollen patterns argue against immediate expansion with the onset of warmer conditions. Despite relatively weak fossil evidence, refugial populations are also probable in eastern Beringia, particularly given the extent of unglaciated terrain. Post‐glacial pollen patterns are more nuanced, suggesting two spatially and temporally distinct expansions, one possibly consistent with a unique central Alaskan haplotype, and subsequent westerly ‘filling‐in’. The presence of macrofossils and/or neutral markers does not require that current northern populations are derived primarily from refugial ones, particularly where pollen patterns show delayed directional expansion of large populations though time. Refugial populations initially responded weakly to major post‐glacial environmental change; if subject to genetic isolation and strong selection pressure they may have had little potential to do otherwise, instead being largely replaced by in‐migrating populations with greater genetic diversity.
DNA preserved in degraded beetle (Coleoptera) specimens, including those derived from dry‐stored museum and ancient permafrost‐preserved environments, could provide a valuable resource for ...researchers interested in species and population histories over timescales from decades to millenia. However, the potential of these samples as genetic resources is currently unassessed. Here, using Sanger and Illumina shotgun sequence data, we explored DNA preservation in specimens of the ground beetle Amara alpina, from both museum and ancient environments. Nearly all museum specimens had amplifiable DNA, with the maximum amplifiable fragment length decreasing with age. Amplification of DNA was only possible in 45% of ancient specimens. Preserved mitochondrial DNA fragments were significantly longer than those of nuclear DNA in both museum and ancient specimens. Metagenomic characterization of extracted DNA demonstrated that parasite‐derived sequences, including Wolbachia and Spiroplasma, are recoverable from museum beetle specimens. Ancient DNA extracts contained beetle DNA in amounts comparable to museum specimens. Overall, our data demonstrate that there is great potential for both museum and ancient specimens of beetles in future genetic studies, and we see no reason why this would not be the case for other orders of insect.
Andrei Sher played a leading role in the development of international cooperation and exchange of ideas in Beringian science. The Cold War created great tensions between the USSR and the NATO ...countries, as the Bering Strait region became one of the front lines of potential military conflict. However, through the persistent efforts of such people as Andrei Sher in Russia and David Hopkins in the USA, scientists were able to overcome political obstacles to attend international Beringian conferences, visit each other’s militarized zones to do fieldwork, and collaborate on joint projects.
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