The area includes land lying on the
North American Plate and Siberian land east of the
Chersky Range. At various times, it formed a
land bridge referred to as the Bering land bridge, that was up to 1,000 kilometres (620 miles) wide at its greatest extent and which covered an area as large as
British Columbia and
Alberta together,[2] totaling approximately 1,600,000 square kilometres (620,000 square miles), allowing biological dispersal to occur between Asia and North America. Today, the only land that is visible from the central part of the Bering land bridge are the
Diomede Islands, the
Pribilof Islands of St. Paul and St. George,
St. Lawrence Island,
St. Matthew Island, and
King Island.[1]
It is believed that a small human population of at most a few thousand arrived in Beringia from eastern Siberia during the
Last Glacial Maximum before expanding into the
settlement of the Americas sometime after 16,500 years
Before Present (YBP).[3] This would have occurred as the American glaciers blocking the way southward melted,[4][5][6][7][8] but before the bridge was covered by the sea about 11,000 YBP.[9][10]
The remains of
Late Pleistocene mammals that had been discovered on the
Aleutians and islands in the
Bering Sea at the close of the nineteenth century indicated that a past land connection might lie beneath the shallow waters between
Alaska and
Chukotka. The underlying mechanism was first thought to be tectonics, but by 1930 changes in the ice mass balance, leading to global sea-level fluctuations were viewed as the cause of the Bering land bridge.[13][14] In 1937,
Eric Hultén proposed that around the Aleutians and the Bering Strait region were tundra plants that had originally dispersed from a now-submerged plain between Alaska and Chukotka, which he named Beringia after the Dane
Vitus Bering who had sailed into the strait in 1728.[15][14] The American arctic geologist David Hopkins redefined Beringia to include portions of Alaska and Northeast Asia. Beringia was later regarded as extending from the
Verkhoyansk Mountains in the west to the
Mackenzie River in the east.[14] The distribution of plants in the genera Erythranthe and Pinus are good examples of this, as very similar genera members are found in Asia and the Americas.[16][17]
During the Pleistocene epoch, global cooling led periodically to the expansion of glaciers and the lowering of sea levels. This created land connections in various regions around the globe.[18] Today, the average water depth of the Bering Strait is 40–50 m (130–160 ft); therefore the land bridge opened when the sea level dropped more than 50 m (160 ft) below the current level.[19][20] A reconstruction of the sea-level history of the region indicated that a seaway existed from
c. 135,000 – c. 70,000 YBP, a land bridge from
c. 70,000 – c. 60,000 YBP, an intermittent connection from c. 60,000 – c. 30,000 YBP, a land bridge from c. 30,000 – c. 11,000 YBP, followed by a Holocene sea-level rise that reopened the strait.[21][22]Post-glacial rebound has continued to raise some sections of the coast.
The
last glacial period, commonly referred to as the "Ice Age", spanned 125,000[23]–14,500YBP[24] and was the most recent
glacial period within the
current ice age, which occurred during the last years of the Pleistocene era.[23] The Ice Age reached its peak during the
Last Glacial Maximum, when
ice sheets began advancing from 33,000YBP and reached their maximum limits 26,500YBP. Deglaciation commenced in the Northern Hemisphere approximately 19,000YBP and in Antarctica approximately 14,500 yearsYBP, which is consistent with evidence that glacial meltwater was the primary source for an abrupt rise in sea level 14,500YBP[24] and the bridge was finally inundated around 11,000 YBP.[10] The fossil evidence from many continents points to the
extinction of large animals, termed
Pleistocene megafauna, near the end of the last glaciation.[25]
During the Ice Age a vast, cold and dry
Mammoth steppe stretched from the
arctic islands southwards to China, and from Spain eastwards across Eurasia and over the Bering land bridge into Alaska and the Yukon where it was blocked by the
Wisconsin glaciation. Therefore, the flora and fauna of Beringia were more related to those of Eurasia rather than North America. Beringia received more moisture and intermittent maritime cloud cover from the north Pacific Ocean than the rest of the Mammoth steppe, including the dry environments on either side of it. This moisture supported a shrub-tundra habitat that provided an
ecological refugium for plants and animals.[26][27] In East Beringia 35,000 YBP, the northern arctic areas experienced temperatures 1.5 °C (2.7 °F) degrees warmer than today but the southern sub-Arctic regions were 2 °C (4 °F) degrees cooler. During the LGM 22,000 YBP the average summer temperature was 3–5 °C (5–9 °F) degrees cooler than today, with variations of 2.9 °C (5.2 °F) degrees cooler on the
Seward Peninsula to 7.5 °C (13.5 °F) cooler in the Yukon.[28] In the driest and coldest periods of the Late Pleistocene, and possibly during the entire Pleistocene, moisture occurred along a north–south gradient with the south receiving the most cloud cover and moisture due to the air-flow from the North Pacific.[27]
In the Late Pleistocene, Beringia was a mosaic of biological communities.[29][26][30] Commencing from
c. 57,000 YBP (
MIS 3), steppe–tundra vegetation dominated large parts of Beringia with a rich diversity of grasses and herbs.[29][26][31] There were patches of shrub tundra with isolated refugia of
larch (Larix) and
spruce (Picea) forests with
birch (Betula) and
alder (Alnus) trees.[29][30][31][32] It has been proposed that the largest and most diverse megafaunal community residing in Beringia at this time could only have been sustained in a highly diverse and productive environment.[33]
Analysis at Chukotka on the Siberian edge of the land bridge indicated that from c. 57,000 – c. 15,000 YBP (MIS 3 to MIS 2) the environment was wetter and colder than the steppe–tundra to the east and west, with warming in parts of Beringia from c. 15,000 YBP.[34] These changes provided the most likely explanation for mammal migrations after c. 15,000 YBP, as the warming provided increased forage for browsers and mixed feeders.[35] At the beginning of the
Holocene, some
mesic habitat-adapted species left the refugium and spread westward into what had become tundra-vegetated northern Asia and eastward into northern North America.[27]
The latest emergence of the land bridge was
c. 70,000 years ago. However, from c. 24,000 – c. 13,000 YBP the
Laurentide Ice Sheet fused with the
Cordilleran Ice Sheet, which blocked gene flow between Beringia (and Eurasia) and continental North America.[36][37][38] The Yukon corridor opened between the receding ice sheets c. 13,000 YBP, and this once again allowed gene flow between Eurasia and continental North America until the land bridge was finally closed by rising sea levels c. 10,000 YBP.[39] During the Holocene, many mesic-adapted species left the refugium and spread eastward and westward, while at the same time the forest-adapted species spread with the forests up from the south. The arid-adapted species were reduced to minor habitats or became extinct.[27]
Beringia constantly transformed its
ecosystem as the changing climate affected the environment, determining which plants and animals were able to survive. The land mass could be a barrier as well as a bridge: during colder periods, glaciers advanced and precipitation levels dropped. During warmer intervals, clouds, rain and snow altered
soils and drainage patterns.
Fossil remains show that
spruce,
birch and
poplar once grew beyond their northernmost range today, indicating that there were periods when the climate was warmer and wetter. The environmental conditions were not homogenous in Beringia. Recent
stable isotope studies of
woolly mammoth bone
collagen demonstrate that western Beringia (
Siberia) was colder and drier than eastern Beringia (
Alaska and
Yukon), which was more ecologically diverse.[40]
Grey wolves suffered a species-wide
population bottleneck (reduction) approximately 25,000 YBP during the Last Glacial Maximum. This was followed by a single population of modern wolves expanding out of their Beringia refuge to repopulate the wolf's former range, replacing the remaining
Late Pleistocene wolf populations across Eurasia and North America.[41][42][43]
The extinct pine species Pinus matthewsii has been described from Pliocene sediments in the Yukon areas of the refugium.[44]
Beringian Gap
The existence of fauna endemic to the respective Siberian and North American portions of Beringia has led to the 'Beringian Gap' hypothesis, wherein an unconfirmed geographic factor blocked migration across the land bridge when it emerged. Beringia did not block the movement of most dry steppe-adapted large species such as saiga antelope, woolly mammoth, and caballid horses.[27] Notable restricted fauna include the
woolly rhino in Siberia (which went no further east than the
Anadyr River), and Arctodus simus,
American badger, American
kiang-like equids, Bootherium and Camelops in North America, with the existence of Homotherium being disputed in Late Pleistocene Siberia. The lack of mastodon and Megalonyx has been attributed to their inhabitation of Alaska and the Yukon being limited to interglacials.[45][46][47] However, ground sloth eDNA has potentially been recovered from Siberia.[48]
The precise date for the peopling of the Americas is a long-standing open question, and while advances in
archaeology,
Pleistocenegeology,
physical anthropology, and
DNA analysis have progressively shed more light on the subject, significant questions remain unresolved.[59][60] The "Clovis first theory" refers to the hypothesis that the
Clovis culture represents the earliest human presence in the Americas about 13,000 years ago.[61]Evidence of pre-Clovis cultures has accumulated and pushed back the possible date of the first peopling of the Americas.[62][63][64][65] Academics generally believe that humans reached North America south of the Laurentide Ice Sheet at some point between 15,000 and 20,000 years ago.[59][62][66][67][68][69] Some new controversial archaeological evidence suggests the possibility that human arrival in the Americas may have occurred prior to the
Last Glacial Maximum more than 20,000 years ago.[62][70][71][72][73]
Around 3,000 years ago, the progenitors of the
Yupik peoples settled along both sides of the straits.[74] The governments of Russia and the United States announced a plan to formally establish "a transboundary area of shared Beringian heritage". Among other things this agreement would establish close ties between the
Bering Land Bridge National Preserve and the
Cape Krusenstern National Monument in the United States and
Beringia National Park in Russia.[75]
The earliest Canis lupus specimen was a fossil tooth discovered at
Old Crow, Yukon, Canada. The specimen was found in sediment dated 1 million YBP,[81] however the geological attribution of this sediment is questioned.[81][82] Slightly younger specimens were discovered at Cripple Creek Sump,
Fairbanks, Alaska, in strata dated 810,000 YBP. Both discoveries point to the origin of these wolves in eastern Beringia during the
Middle Pleistocene.[81]
Fossil evidence also indicates an exchange of primates and plants between North America and Asia around 55.8 million years ago.[76][83][84] 20 million years ago, evidence in North America shows the last natural interchange of mammalian species. Some, like the ancient
saber-toothed cats, have a recurring geographical range: Europe, Africa, Asia, and North America.[76]
^
abShared Beringian Heritage Program.
"What is Beringia?". National Park Service, US Department of the Interior.
^Dr Barbara Winter (2005).
"A Journey to a New Land". www.sfu.museum. virtualmuseum.ca. Archived from
the original on 28 April 2015. Retrieved 19 May 2015.
^Hopkins DM. 1967. Introduction. In: Hopkins DM, editor. The Bering land bridge. Stanford: Stanford University Press. pp. 1–6.
^
abcHoffecker, John F.; Elias, Scott A.; O'Rourke, Dennis H.; Scott, G. Richard; Bigelow, Nancy H. (2016). "Beringia and the global dispersal of modern humans". Evolutionary Anthropology: Issues, News, and Reviews. 25 (2): 64–78.
doi:
10.1002/evan.21478.
PMID27061035.
S2CID3519553.
^Hultén E. 1937. Outline of the history of arctic and boreal biota during the Quaternary Period. New York: Lehre J. Cramer.
^
abcElias SA, Crocker B. 2008 The Bering land bridge: a moisture barrier to the dispersal of steppe-tundra biota? Q. Sci. Rev. 27, 2473–83
^
abcdeGuthrie RD. 2001 Origin and causes of the mammoth steppe: a story of cloud cover, woolly mammal tooth pits, buckles, and inside-out Beringia. Q. Sci. Rev. 20, 549–74.
^
abSher AV, Kuzmina SA, Kuznetsova TV, Sulerzhitsky LD. 2005 New insights into the Weichselian environment and climate of the East Siberian Arctic, derived from fossil insects, plants, and mammals. Q. Sci. Rev. 24, 533–69.
^Anderson PH, Lozhkin AV. 2001 The Stage 3 interstadial complex (Karginskii/middle Wisconsinan interval) of Beringia: variations in paleoenvironments and implications for paleoclimatic interpretations. Q. Sci. Rev. 20, 93–125
^Guthrie RD. 1982 Mammals of the mammoth steppe as paleoenvironmental indicators. In Paleoecology of Beringia (eds Hopkins DM, Matthews JV, Schweger CE, Young SB), pp. 307–24. New York: Academic Press
^Kuzmina SA, Sher AV, Edwards ME, Haile J, Yan EV, Kotov AV, Willerslev E. 2011 The late Pleistocene environment of the Eastern West Beringia based on the principal section at the Main River, Chukotka. Q. Sci. Rev. 30, 2091–2106
^Gowan, E.J. (2013) An assessment of the minimum timing of ice free conditions of the western Laurentide Ice Sheet. Quaternary Science Review, 75, 100–13.
^Rabassa, J.; Ponce, J.F. (2013). "The Heinrich and Dansgaard-Oeschger climatic events during Marine Isotopic Stage 3:searching for appropriate times for human colonization of the America". Quaternary International. 299: 94–105.
Bibcode:
2013QuInt.299...94R.
doi:
10.1016/j.quaint.2013.04.023.
hdl:
11336/26736.
^Koblmüller, Stephan; Vilà, Carles; Lorente-Galdos, Belen; Dabad, Marc; Ramirez, Oscar; Marques-Bonet, Tomas; Wayne, Robert K.; Leonard, Jennifer A. (2016). "Whole mitochondrial genomes illuminate ancient intercontinental dispersals of grey wolves (Canis lupus)". Journal of Biogeography. 43 (9): 1728.
Bibcode:
2016JBiog..43.1728K.
doi:
10.1111/jbi.12765.
S2CID88740690.
^Chatters, James C.; Potter, Ben A.; Prentiss, Anna Marie; Fiedel, Stuart J.; Haynes, Gary; Kelly, Robert L.; Kilby, J. David; Lanoë, François; Holland-Lulewicz, Jacob; Miller, D. Shane; Morrow, Juliet E.; Perri, Angela R.; Rademaker, Kurt M.; Reuther, Joshua D.; Ritchison, Brandon T.; Sanchez, Guadalupe; Sánchez-Morales, Ismael; Spivey-Faulkner, S. Margaret; Tune, Jesse W.; Haynes, C. Vance (October 23, 2021). "Evaluating Claims of Early Human Occupation at Chiquihuite Cave, Mexico". PaleoAmerica. 8 (1). Informa UK Limited: 1–16.
doi:
10.1080/20555563.2021.1940441.
ISSN2055-5563.
S2CID239853925.
^Bryant, Vaughn M. Jr. (1998).
"Pre-Clovis". In Guy Gibbon; et al. (eds.). Archaeology of Prehistoric Native America: An Encyclopedia. Garland reference library of the humanities. Vol. 1537. pp. 682–683.
ISBN978-0-8153-0725-9.
^Westgate, John A; Pearce, G. William; Preece, Shari J; Schweger, Charles E; Morlan, Richard E; Pearce, Nicholas J.G; Perkins, T. William (2017). "Tephrochronology, magnetostratigraphy and mammalian faunas of Middle and Early Pleistocene sediments at two sites on the Old Crow River, northern Yukon Territory, Canada". Quaternary Research. 79: 75–85.
doi:
10.1016/j.yqres.2012.09.003.
S2CID140572760.