CU study – Bering Land Bridge long-term habitat for earliest Americans

February 27, 2014

Feb. 27, 2014                                                           John Hoffecker

            A new study led by CU-Boulder strengthens the theory that the first Americans, believed to have migrated over the Bering Land Bridge from Asia, may have settled in the region instead of quickly migrating into the Americas as other theories have suggested.  

            The theory, known as the “Beringian Standstill,” was first proposed in 1997 and refined in 2007 by a team led by the University of Illinois who sampled mitochondrial DNA from more than 600 Native Americans.

           According to CU-Boulder Research Associate John Hoffecker, lead author of the study, they found that mutations in the DNA indicated a group of their direct ancestors from Siberia was likely isolated for thousands of years in the land bridge region.

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CU study – Bering Land Bridge long-term habitat for earliest Americans

Feb. 27, 2014                                                           John Hoffecker

            A new study led by CU-Boulder strengthens the theory that the first Americans, believed to have migrated over the Bering land bridge from Asia, may have settled in the region instead of quickly migrating into the Americas as other theories have suggested.  

            The theory, known as the “Beringian Standstill,” was first proposed in 1997 and refined in 2007 by a team led by the University of Illinois who sampled mitochondrial DNA from more than 600 Native Americans.

          According to CU-Boulder Research Associate John Hoffecker, lead author of the study, they found that mutations in the DNA indicated a group of their direct ancestors from Siberia was likely isolated for thousands of years in the land bridge region.

CUT 1 “What the genetics show is that most Native Americans, other than the most recent arrivals that live in North America such as the Eskimo, the Inuit, the Aleuts and Athabaskans, diverged from their Asian source populations at a much earlier time than we had thought based on the age of the earliest archaeological sites in North and South America. (:23) Therefore it becomes important to explain this genetic divergence through this ‘Beringia Standstill’ model.” (:30)

            Beringia was a large landmass that stretched between present day Alaska and Siberia during the last ice age around 20,000 to 30,000 years ago when oceans were 400 feet lower due to water frozen in massive glaciers and ice sheets.

            Hoffecker says for years archaeologists never considered that region as a place where humans could have survived the last ice age -- that is until they started to pay attention to studies conducted by ecologists and geneticists indicating the climate there was much more habitable than they thought.

CUT 2 “It seemed to us that Beringia would be the last place on Earth where you would have a large population surviving during the coldest period of the last glacial. (:08) What has happened here is that a geneticist, an archaeologist and an ecologist got together and came to the conclusion that the ecological data fit this hypothesis very nicely. The environment in central Beringia seems to have been much wetter, characterized by more tundra-type communities of vegetation. It probably included some woody shrubs and also a few trees. And wood may have been the key to human survival.” (:35)

            The key to survival because prehistoric people living in northern regions during the last ice age burned large mammal bones for fuel and they needed wood to create fires hot enough to ignite the bones.

CUT 3 “We know from experimental studies that bone burns very hot and fast and if you are going to be burning a lot of bone, in order to make practical as a fuel, you need to supplement it with at least a little wood. (13) And sure enough when we look at the archaeology of people’s living in areas where wood was scarce we find heavy use of bone but always find a little wood in there.” (:22)

 

It is believed that the population of the group numbered a few thousand and that they were very diverse by the time they migrated south from Beringia into the Americas.

CUT 4 “The geneticists are telling us that the population was fairly large.  We’re talking about at least a few thousand people here. And it was a population that was doing quite well. (:10) And the genetics show that the genetic diversity of the population was actually increasing during this period of isolation. And we now have 16 identified mitochondrial maternal DNA maternal lineages coming out of Beringia at the time people began dispersing into North and South America.” (:28)

            Hoffecker says a good example of how divergent this group had become was the discovery of a the remains of a prehistoric man in the 1990s called the “Kennewick Man,” found on a bank of the Columbia River in Kennewick, Washington. Bone tests date the remains from 7300 to 7600 B.C.

CUT 5 “A few years ago we recovered some skeletal remains -- the Kennewick Man remains.  And it was noted they don’t look like modern Asians -- the remains of a modern Asian. They look quite different. They are more sort of generic. And I think that the ‘Beringia Standstill’ hypothesis helps explain this apparent dilemma. (:19) The Kennewick man makes perfect sense as the descendant of a group of people who diverged over 30,000 years ago from the then inhabitants of Northeast Asia and not, say, 12,000 years ago.” (:32)

            13,000 years ago temperatures warmed and glaciers covering much of North America receded creating ice-free corridors that the Beringian people used to migrated south into the Americas.

            Hoffecker is a researcher with INSTARR, the Institute of Arctic and Alpine Research at CU-Boulder. 

-CU-

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