Posts tagged Bering Land Bridge
Asian migrants stuck on land bridge for milleniums
Feb 27th
CU-Boulder-led study says Bering Land Bridge area
likely a long-term refuge for early Americans
likely a long-term refuge for early Americans
A new study led by the University of Colorado Boulder bolsters the theory that the first Americans, who are believed to have come over from northeast Asia during the last ice age, may have been isolated on the Bering Land Bridge for thousands of years before spreading throughout the Americas.
The theory, now known as the “Beringia Standstill,” was first proposed in 1997 by two Latin American geneticists and refined in 2007 by a team led by the University of Tartu in Estonia that sampled mitrochondrial DNA from more than 600 Native Americans. The researchers found that mutations in the DNA indicated a group of their direct ancestors from Siberia was likely isolated for at least several thousand years in the region of the Bering Land Bridge, the now-submerged plain that lies between northeast Asia and Alaska once exposed by a significantly lower sea level.
CU-Boulder researcher John Hoffecker, lead author of a short paper article appearing in the Feb. 28 issue of Science magazine, said the Beringia Standstill model gained little traction outside of the genetics community after it was proposed and has been seen by some scientists outside of the field as far-fetched. But the new paper by Hoffecker and co-authors Scott Elias of Royal Holloway, University of London, and Dennis O’Rourke of the University of Utah adds credence to the Beringia Standstill idea by further linking the genetics to the paleoecological evidence.
The Beringia Land Bridge was relatively temperate during the last ice age
“A number of supporting pieces have fallen in place during the last decade, including new evidence that central Beringia supported a shrub tundra region with some trees during the last glacial maximum and was characterized by surprisingly mild temperatures, given the high latitude,” said Hoffecker of CU-Boulder’s Institute of Arctic and Alpine Research. The last glacial maximum peaked roughly 21,000 years ago and was marked by the growth of vast ice sheets in North America and Europe.
While a debate rages on about when early humans first migrated into the New World, many archaeologists now believe it was sometime around 15,000 years ago after retreating glaciers opened access to coastal and interior routes into North America.
The relatively mild summer climate in Beringia at the time was caused by North Pacific circulation patterns that brought moist and relatively warm air to the region during the last glacial maximum. Geologists believe the Beringia gateway between Siberia and Alaska was more than 600 miles wide at the time.
Hoffecker and others are now theorizing that a population of hundreds or thousands of people parked itself in central Beringia for 5,000 years or more. One key to the extended occupation may have been the presence of wood in some places to use as a fuel to supplement bone, which burns hot and fast. Experiments have shown that at least some wood is necessary to make bone practical as a fuel.
Elias, a paleoecologist and also an INSTAAR affiliate, said research using fossil pollen, plant and insect material from sediment cores from the now submerged landscape show that the Bering Land Bridge tundra environment contained enough woody plants and trees like birch, willow and alder to provide a supplement to bone.
Work by Elias and others included the analysis of certain beetle species that live in very specific temperature zones, allowing them to be used as tiny thermometers. The insects indicated that temperatures there were relatively mild during last glacial maximum that ran from about 27,000 years to 20,000 years ago, only slightly cooler than temperatures in the region today.
“The climate on the land bridge and adjacent parts of Siberia and Alaska was a bit wetter than the interior regions like central Alaska and the Yukon, but not a lot warmer,” said Elias. “Our data show that woody shrubs were available on the land bridge, which would have facilitated the making of fires by the people there.”
Evidence from the 2007 study indicated a set of genetic mutations in mitochondrial DNA, which is passed down from mother to offspring, clearly accumulated after the divergence of people from their Asian parent groups in Siberia but before their dispersal throughout the Western Hemisphere, said O’Rourke. In addition, ancient DNA from human skeletal remains found at a 24,000-year-old archaeological site in southern Siberia also appears consistent with the divergence of Native American groups from their Asian forbearers by that time window, he said.
“The genetic record has been very clear for several years that the Native American genome must have arisen in an isolated population at least by 25,000 years ago, and the bulk of the migrants to the Americas really didn’t arrive south of the ice sheets until nearly 15,000 years ago,” O’Rourke said. “The paleoecological data, which I think most geneticists have not been familiar with, indicate that Beringia was not a uniform environment, and there was a shrub tundra region, or refugium, that likely provided habitats conducive to continuous human habitation.”
“From my view the genetics and paleoecology data come together nicely,” said Hoffecker, who co-authored a 2007 book with Elias titled “The Human Ecology of Beringia.” While the weakest link to the Out of Beringia theory is the lack of archaeological evidence, Hoffecker believes future research on now submerged parts of Beringia as well as lowlands in western Alaska and eastern Siberia that still remain above water may hold clues to ancient habitation by Beringia residents, who eventually moved on to be the first group to inhabit the Americas.
Hoffecker also believes that the Beringia inhabitants during the last glacial maximum could have made successful hunting forays into the uninhabited steppe-tundra region to both the east and west, where drier conditions and more grass supported a plentiful array of large grazing animals, including steppe bison, horse and mammoth.
There is now solid evidence for humans in Beringia before the last glacial maximum, as geneticists first predicted in 1997, said Hoffecker. After the maximum, there are two sets of archaeological remains dating to less than 15,000 years ago. “One represents a late migration from Asia into Alaska at that time,” he said. “The other has no obvious source outside Beringia and may represent the people who are thought to have sheltered on the land bridge during the glacial maximum.
“If we are looking for a place to put all of these people during the last glacial maximum, Beringia may be the only realistic option,” said Hoffecker.
A video news story on the research is available at http://www.colorado.edu/news.
-CU-
CU Boulder scientists uncover molded brass artifact from Asia in Alaska
Nov 14th
ANCIENT BRONZE ARTIFACT FROM EAST ASIA
UNEARTHED AT ALASKA ARCHAEOLOGY SITE
UNEARTHED AT ALASKA ARCHAEOLOGY SITE
A team of researchers led by the University of Colorado Boulder has discovered the first prehistoric bronze artifact made from a cast ever found in Alaska, a small, buckle-like object found in an ancient Eskimo dwelling and which likely originated in East Asia.
The artifact consists of two parts — a rectangular bar, connected to an apparently broken circular ring, said CU-Boulder Research Associate John Hoffecker, who is leading the excavation project. The object, about 2 inches by 1 inch and less than 1 inch thick, was found in August by a team excavating a roughly 1,000-year-old house that had been dug into the side of a beach ridge by early Inupiat Eskimos at Cape Espenberg on the Seward Peninsula, which lies within the Bering Land Bridge National Preserve.
Both sections of the artifact are beveled on one side and concave on the other side, indicating it was manufactured in a mold, said Hoffecker, a fellow at CU-Boulder’s Institute of Arctic and Alpine Research. A small piece of leather found wrapped around the rectangular bar by the research team yielded a radiocarbon date of roughly A.D. 600, which does not necessarily indicate the age of the object, he said.
“I was totally astonished,” said Hoffecker. “The object appears to be older than the house we were excavating by at least a few hundred years.”.
Hoffecker and his CU-Boulder colleague Owen Mason said the bronze object resembles a belt buckle and may have been used as part of a harness or horse ornament prior to its arrival in Alaska. While they speculated the Inupiat Eskimos could have used the artifact as a clasp for human clothing or perhaps as part of a shaman’s regalia, its function on both continents still remains a puzzle, they said.
Since bronze metallurgy from Alaska is unknown, the artifact likely was produced in East Asia and reflects long-distance trade from production centers in either Korea, China, Manchuria or southern Siberia, according to Mason. It conceivably could have been traded from the steppe region of southern Siberia, said Hoffecker, where people began casting bronze several thousand years ago.
Alternatively, some of the earliest Inupiat Eskimos in northwest Alaska — the direct ancestors of modern Eskimos thought to have migrated into Alaska from adjacent Siberia some 1,500 years ago — might have brought the object with them from the other side of the Bering Strait. “It was possibly valuable enough so that people hung onto it for generations, passing it down through families,” said Mason, an INSTAAR affiliate and co-investigator on the Cape Espenberg excavations.
The Seward Peninsula is a prominent, arrowhead-shaped land mass that abuts the Bering Strait separating Alaska from Siberia. The peninsula was part of the Bering Land Bridge linking Asia and North America during the last ice age when sea level had dropped dramatically, and may have been used by early peoples as a corridor to migrate from Asia into the New World some 14,000 years ago.
The artifact was discovered in August by University of California, Davis, doctoral student Jeremy Foin under 3 feet of sediment near an entryway to a house at Cape Espenberg. Other project members included Chris Darwent of UC Davis, Claire Alix of the University of Paris, Nancy Bigelow of the University of Alaska Fairbanks, Max Friesen of the University of Toronto and Gina Hernandez of the National Park Service.
“The shape of the object immediately caught my eye,” said Foin, who spotted the soil-covered artifact in an archaeological sifting screen. “After I saw that it clearly had been cast in a mold, my first thought was disbelief, quickly followed by the realization that I had found something of potentially great significance.”
The CU-led excavations are part of a National Science Foundation-funded project designed to study human response to climate change at Cape Espenberg from A.D. 800 to A.D. 1400, a critical period of cultural change in the western Arctic, said Mason. Of particular interest are temperature and environmental changes that may be related to Earth’s Medieval Warm Period that lasted from about A.D. 950 to 1250.
“That particular time period is thought by some to be an analog of what is happening to our environment now as Earth’s temperatures are rising,” said Mason. “One of our goals is to find out how these people adapted to a changing climate through their subsistence activities.”
The Cape Espenberg beach ridges, wave-swept deposits made of sand and sediment running parallel to the shoreline that were deposited over centuries, often are capped by blowing sand to form high dunes. The Cape Espenberg dwellings were dug into the dunes and shored up with driftwood and occasional whale bones.
The team is examining the timing and formation of the beach ridges as well as the contents of peat and pond sediment cores to help them reconstruct the sea-level history and the changing environment faced by Cape Espenberg’s settlers. Information on past climates also is contained in driftwood tree rings, and the team is working with INSTAAR affiliate Scott Elias, a University of London professor and expert on beetle fossils, who is helping the team reconstruct past temperatures at Cape Espenberg.
While the hunting of bowhead whales was a way of life for Inupiat Eskimos at Barrow and Point Hope in northwestern Alaska 1,000 years ago, it is still not clear if the Cape Espenberg people were whaling, said Mason. While whale baleen — a strong, flexible material found in the mouths of whales that acts as a food filter — and a variety of whale bones have been found during excavations there, the sea offshore is extremely shallow and some distance from modern whale migration routes. However, there is evidence of fishing and seal and caribou hunting by the group, he said.
The Inupiat Eskimos are believed to have occupied Cape Espenberg from about A.D. 1000 until the mid-1800s, said Hoffecker. They are part of the indigenous Eskimo culture that lives in Earth’s circumpolar regions like Alaska, Siberia and Canada.
The Cape Espenberg site has yielded a treasure trove of several thousand artifacts, including sealing harpoons, fishing spears and lures, a copper needle, slate knives, antler arrow points, a shovel made from a walrus scapula, a beaver incisor pendant, ceramics, and even toy bows and toy harpoons. The bronze artifact unearthed in August is currently under study by prehistoric metallurgical expert and Purdue University Assistant Professor H. Kory Cooper.
A video news story on the discovery is available by going to http://www.colorado.edu/news/ and clicking on the story headline. A podcast on the find can be found at http://www.colorado.edu/news/podcasts/
