Nautical chart of Bering Strait, site of former land bridge between Asia and North America

Shrinking of the Bering land bridge

The Bering land bridge was a land bridge roughly 1,000 miles (1,600 km) north to south at its greatest extent, which joined present-day Alaska and eastern Siberia at various times during the Pleistocene ice ages. It was not glaciated because snowfall was extremely light due to the southwesterly winds from the Pacific Ocean having lost their moisture over the fully glaciated Alaska Range. The grassland steppe including the land bridge and stretching for several hundred miles either side of it has been called Beringia. Image File history File links This image was produced from ENC S-57 data supplied by the US NOAA Office of Coast Survey, chart US1BS03M, and is free from copyright. ... Image File history File links This image was produced from ENC S-57 data supplied by the US NOAA Office of Coast Survey, chart US1BS03M, and is free from copyright. ... A 1976 United States NOAA chart of part of Puerto Rico A nautical chart is a graphic representation of a maritime area and adjacent coastal regions. ... Satellite photo of the Bering Strait Photo across the Bering Strait Nautical chart of the Bering Strait The Bering Strait (Russian: ) is a sea strait between Cape Dezhnev, Russia, the easternmost point (169°43 W) of the Asian continent and Cape Prince of Wales, Alaska, the westernmost point (168°05... For other uses, see Asia (disambiguation). ... North American redirects here. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... This article or section does not cite its references or sources. ... For other uses, see Alaska (disambiguation). ... This article is about Siberia as a whole. ... The Pleistocene epoch (IPA: ) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the worlds recent period of repeated glaciations. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Perito Moreno Glacier Patagonia Argentina Aletsch Glacier, Switzerland Icebergs breaking off glaciers at Cape York, Greenland This article is about the geological formation. ... For other uses, see Snow (disambiguation). ... For the Australian television series see Rain Shadow (TV series). ... This article is about the ecological zone type. ...

It is believed that a small human population of at most a few thousand may have survived the last ice age in Beringia, isolated from its ancestor populations in Asia for at least 5,000 years; before expanding to populate the Americas sometime after 16,500 years ago, as the American glaciers blocking the way southward melted.^[1][2][3][4] Temperature proxies for the last 40,000 years The Last Glacial Maximum refers to the time of maximum extent of the ice sheets during the last glaciation, approximately 21 thousand years ago. ... There are several popular models of migration to the New World proposed by the anthropological community. ...

Geography

The Bering Strait, the Chukchi Sea to the north and the Bering Sea to the south, are all shallow seas (map, right). During cycles of global cooling, such as the most recent ice age, enough sea water became concentrated in the ice caps of the Arctic and Antarctic that the subsequent drop in eustatic sea levels exposed shallow sea floors. Other land bridges around the world have been created and re-flooded in the same way: approximately 14,000 years ago, mainland Australia was linked both to New Guinea and to Tasmania, the British Isles were an extension of continental Europe via the English Channel, and the dry basin of the South China Sea linked Sumatra, Java and Borneo to the Asian mainland. Satellite photo of the Bering Strait Photo across the Bering Strait Nautical chart of the Bering Strait The Bering Strait (Russian: ) is a sea strait between Cape Dezhnev, Russia, the easternmost point (169°43 W) of the Asian continent and Cape Prince of Wales, Alaska, the westernmost point (168°05... Chukchi Sea (Russian: Чуко́тское мо́ре) is a marginal sea of the Arctic Ocean, between Chukotka and Alaska. ... Satellite photo of the Bering Sea Bering Sea and the North Pacific Ocean Bearing Sea with Kamchatka Peninsula and Alaska The Bering (or Imarpik) Sea is a body of water north of, and separated from, the north Pacific Ocean by the Alaska Peninsula and Aleutian Islands. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... For the ships, see USS Arctic, SS Arctic, MV Arctic The red line indicates the 10°C isotherm in July, sometimes used to define the Arctic region border Artificially coloured topographical map of the Arctic region The Arctic is the region around the Earths North Pole, opposite the Antarctic... Greek ἀνταρκτικός, opposite the arctic) is a continent surrounding the Earths South Pole. ... It has been suggested that this article or section be merged with sea level. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ... Slogan or Nickname: Island of Inspiration; The Apple Isle; Holiday Isle Motto(s): Ubertas et Fidelitas (Fertility and Faithfulness) Other Australian states and territories Capital Hobart Government Constitutional monarchy Governor William Cox Premier Paul Lennon (ALP) Federal representation  - House seats 5  - Senate seats 12 Gross State Product (2004-05)  - Product... This article explains the archipelago in north-western Europe. ... For other uses, see Europe (disambiguation). ... For the Thoroughbred racehorse of the same name, see English Channel (horse). ... Filipino name Tagalog: Timog Dagat Tsina (Dagat Luzon for the portion within Philippine waters) Malay name Malay: Laut China Selatan Portuguese name Portuguese: Mar da China Meridional Vietnamese name Vietnamese: The South China Sea is a marginal sea south of China. ... For other uses, see Sumatra (disambiguation). ... Java (Indonesian, Javanese, and Sundanese: Jawa) is an island of Indonesia, and the site of its capital city, Jakarta. ... Φ Borneo is the third largest island in the world and is located at the centre of Maritime Southeast Asia. ... For other uses, see Asia (disambiguation). ...

The rise and fall of global sea levels has exposed and submerged the land bridge in several periods of the Pleistocene. The bridging land mass called "Beringia" is believed to have existed both in the glaciation that occurred before 35,000 BC and during the more recent period 22,000-7,000 years ago. By c. 4000 BC the coastlines had assumed approximately their present configurations. The Pleistocene epoch (IPA: ) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the worlds recent period of repeated glaciations. ... A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ...

Beringia constantly transformed its ecology 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 poplars once grew beyond their northernmost modern range today, indicating there were periods when the climate was warmer and wetter. Mastodons, which depended on shrubs for food, were uncommon in the open dry tundra landscape characteristic of Beringia during the colder periods; in this tundra, mammoths flourished instead. For the journal, see Ecology (journal). ... For other uses, see Snow (disambiguation). ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For other uses, see Soil (disambiguation). ... For other uses, see Fossil (disambiguation). ... Species About 35; see text. ... Species Many species; see text and classification Birch is the name of any tree of the genus Betula, in the family Betulaceae, closely related to the beech/oak family, Fagaceae. ... This article is about woody plants of the genus Populus. ... This article is about the prehistoric elephant-like animal. ... For other uses, see Tundra (disambiguation). ... This article is about the genus Mammuthus. ...

Human habitation

Main article: Models of migration to the New World

The Bering land bridge is significant for several reasons, not least because it is believed to have enabled human migration to the Americas from Asia about 25,000 years ago.^[5] A study by Hey (2005)^[6] have indicated that of the people migrating across this land bridge during that time period, only 70 left their genetic print in modern descendants, a minute effective founder population—easily misread as though implying that only 70 people crossed to North America. Sea-going coastal settlers may also have crossed much earlier, but scientific opinion remains divided on this point, and the coastal sites that would offer further information now lie submerged in up to a hundred metres of water offshore. Land animals were able to migrate through Beringia as well, bringing mammals that evolved in Asia to North America, mammals such as proboscideans and lions, which evolved into now-extinct endemic North American species, and allowing equids and camelids that evolved in North America (and later became extinct there) to migrate to Asia. There are several popular models of migration to the New World proposed by the anthropological community. ... Net migration rates for 2006: positive (blue), negative (orange) and stable (green). ... When a species invades a new area, especially an island, the original, small population is called a founder population. ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria For the folk-rock band see The Mammals. ... North American redirects here. ... Groups Jozaria (extinct) Anthracobunidae (extinct) Moeritheriidae (extinct) Euproboscidea Numidotheriidae (extinct) Barytheriidae (extinct) Deinotheriidae (extinct) Elephantiformes Phiomiidae (extinct) Palaeomastodontidae (extinct) Hemimastodontidae (extinct) Euelephantoidea Choerolophodontidae (extinct) Amebelodontidae (extinct) Gnathabelodontidae (extinct) Gomphotheriidae (extinct) Elephantidae Mammutidae (extinct) Proboscidea is an order containing only one family of living animals, Elephantidae, the elephants, with three species... The term American lion has sometimes been used to mean the cougar Trinomial name Panthera leo atrox (Leidy, 1853) The American lion (Panthera leo atrox) also known as the North American lion or American cave lion, is an extinct feline known from fossils. ... This article is about evolution in biology. ... In biology and ecology endemic means exclusively native to a place or biota, in contrast to cosmopolitan or introduced. ... Species - Donkey - African Wild Ass - Domestic Horse - Wild Horse - Grevys Zebra - Onager - Kiang - Plains Zebra - Cape Mountain Zebra - Hartmanns Mountain Zebra Equidae is the family of horse-like animals, order Perissodactyla. ... Map of the world showing distribution of camelids. ...

A new study published November 26, 2007 (see PLoS Genetics), which was led by University of Michigan and University College London researchers, seems to suggest that the Bering land bridge migration occurred during one specific time period which was 12,000 years ago, that every human who migrated across the land bridge all came from Eastern Siberia during that time period, and that every native American is directly descended from that same group of Eastern Siberian migrants.^[7] The claim suggests that a "unique genetic variant widespread in natives across both continents — suggesting that the first humans in the Americas came in a single migration or multiple waves from a single source, not in waves of migrations from different sources".

Previous connections

Biogeographical evidence demonstrates previous connections between North America and Asia. Similar dinosaur fossils have been found between Asia and North America. For instance the dinosaur Saurolophus was found in both Mongolia and western North America. Relatives of Troodon, Triceratops, and even Tyrannosaurus rex all came from Asia. Biogeography is the science which deals with patterns of species distribution and the processes that result in such patterns. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ... For other uses, see Asia (disambiguation). ... North American redirects here. ... Binomial name Saurolophus osborni Brown, 1912 Species S osborni S. angustirostris Rozhdestvensky, 1952 Saurolophus is a large hadrosaurid. ... Binomial name Troodon formosus Leidy, 1856 Troodon formosus was a relatively small, bird-like dinosaur from the late Cretaceous Period (68–65 MYA). ... Species (type) Marsh, 1890 Triceratops (IPA: ) was a herbivorous genus of ceratopsid dinosaur that lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago (mya) in what is now North America. ... Binomial name Tyrannosaurus rex Osborn, 1905 Synonyms Manospondylus gigas Dynamosaurus imperiosus Dinotyrannus megagracilis Nanotyrannus lancensis? Tyrannosaurus (IPA pronunciation or ; from the Greek τυραννόσαυρος, meaning tyrant lizard) is a genus of tyrannosaurid theropod dinosaur. ...

However, while there is considerable evidence for faunal interchange of dinosaurs in the Campanian and Maastrichtian phases of the Late Cretaceous, mammals seem not to have dispersed so easily, perhaps because of their relatively small size; at any rate, there is no direct evidence supporting mammalian faunal exchange in the Cretaceous^[8]. Fossils in China demonstrate a migration of Asian mammals into North America around 55 million years ago. By 20 million years ago, evidence in North America shows a further interchange of mammalian species. Some, like the ancient saber-toothed cats, have a recurring geographical range: Europe, Africa, Asia, and North America. The only way they could reach the New World is through the Bering land bridge. Had this bridge not existed at that time, the fauna of the world would be very different. The fossilized skeleton of a saber-toothed cat (Smilodon californicus). ... Frontispiece of Peter Martyr dAnghieras De orbe novo (On the New World). Carte dAmérique, Guillaume Delisle, 1722. ...

Most recently, molecular phylogenetics is now being used to trace the history of faunal exchange and diversification, through the genetic history of parasites and pathogens of North American ungulates. An international Beringian Coevolution Project is collaborating to provide material to assess the pattern and timing of faunal exchange and the potential impact of past climatic events on differentiation. Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic. ... Ungulates (meaning roughly hoofed or hoofed animal) make up several orders of mammals, of which six survive: Artiodactyla: even-toed ungulates, cattle, sheep, goats, pigs, antelope, and many others Cetacea: whales and dolphins (which evolved from hoofed land animals) Perissodactyla: odd-toed ungulates such as horses and rhinos Proboscidea: elephants...

References

Science, the journal of the American Association for the Advancement of Science (AAAS), is one of the worlds most prestigious scientific publications. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Since its inception in 1948, The American Journal of Human Genetics has provided a record of research and review relating to heredity in humans and to the application of genetic principles in medicine and public policy, as well as in related areas of molecular and cell biology. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... PLoS ONE is an open access, online scientific journal from the Public Library of Science. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... PLoS Biology is a scientific journal covering the full spectrum of the biological sciences it began operation on October 13, 2003. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... PLoS Genetics is a magazine that was created in August 2005. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links

• Bering Land Bridge National Preserve
• "The Bering Strait Crossing" by James A. Oliver ISBN 0954699564 Information Architects 2006 & 2007 (Revised)
• What is Beringia?
• D.K. Jordan, "Prehistoric Beringia"
• Paleoenvironmental atlas of Beringia: includes animation showing the gradual disappearance of the Bering land bridge
• Yukon Beringia Interpretive Centre
• Paleoenvironments and Glaciation in Beringia
• Anne Weil, 2002. "Late Cretaceous and early Paleocene mammalian exchange between Asia and North America"
• Study suggests 20000 year hiatus in Beringia
• Mitochondrial Population Genomics Supports a Single Pre-Clovis Origin with a Coastal Route for the Peopling of the Americas, American Journal of Human Genetics, 82 (3), 583-592 (3 March 2008). pdf file of article (525kb)

Since its inception in 1948, The American Journal of Human Genetics has provided a record of research and review relating to heredity in humans and to the application of genetic principles in medicine and public policy, as well as in related areas of molecular and cell biology. ...

Further reading

• Pielou, E. C., After the Ice Age : The Return of Life to Glaciated North America 1992
• Hey, Jody, 2005. "On the Number of New World Founders: A Population Genetic Portrait of the Peopling of the Americas" in PLoS Biol 2005 May 24;3(6):e193 [2]

See also

• Wisconsinan glaciation
• Pleistocene epoch
• Geologic time scale
• Bering Strait Bridge