Posted on 10/19/2006 4:54:13 PM PDT by blam
New Land-Bridge Evidence Adds to Mystery of 1st Americans
Adrianne Appel
for National Geographic News
October 18, 2006
The long-gone land bridge between Asia and Alaska—a route possibly followed by the first humans to reach the Americas—flooded about 12,000 years ago, a new study suggests.
That's about a thousand years earlier than previously thought, adding to evidence that humans may have reached the Americas by other means.
"I think we're on the verge of rewriting the whole history of the region," said study leader Lloyd Keigwin of Woods Hole Oceanographic Institution in Massachusetts.
The new evidence from the Arctic also suggests that the thousand-mile-wide (1,609-kilometer-wide) bridge was available for a much shorter time than previously believed.
Unconventional Wisdom
The commonly held theory is that humans migrated across the Pacific during the last ice age, which ended around 11,500 years ago.
During the Ice Age much of Earth's water was locked up in glaciers, resulting in lower sea levels that exposed land previously underwater. The land bridge north of the Bering Sea that once linked Siberia and Alaska, is one example.
As the Ice Age ended and glaciers melted, sea levels rose, eventually swamping the Bering land bridge—but when?
Keigwin's team collected data suggesting that the bridge flooded not 11,000 years ago, as is widely believed, but closer to 12,000 years ago.
The new results appear in the October issue of the journal Geology.
The report adds to a growing body of research that challenges the idea that the only route the Americas was a single land bridge from Asia around 12,000 years ago.
Sediments as Evidence
To determine the dates of the flooding, Keigwin's team collected cylindrical samples of Hope Valley. The valley was once part of the bridge but is now part of the floor of the Arctic Ocean's Chukchi Sea.
The scientists radiocarbon-dated and otherwise tested fossilized shells in the layered seafloor sediment. These readings helped the team determine what the climate was like during the time periods represented by the different layers in any given sample.
The now submerged Hope Valley, the researchers found, was flooded close to 12,000 years ago.
By Land and by Sea?
Some scientists now believe early humans migrated to the Americas from Asia in boats or by land over a much longer period of time.
"They may have done both, depending on the timing," said Vance Holliday, a geoscientist and anthropologist at the University of Arizona in Tucson.
"It's good to have this sort of data. This whole story is surprisingly poorly reported—of when the ice-free corridor was opened and closed," Holliday said.
Many scientists began to question the prevailing land-bridge theory in 1997. In that year researchers verified that human artifacts in Monte Verde, Chile, date back to an average of about 12,500 years ago.
Some scientists believe it is unlikely that people could have crossed the Arctic bridge during the time it was passable and still have made it south to Chile by 12,500 years ago.
Also, archaeological sites in the high Arctic have been dated at 29,000 years ago—long before the period of heavy glaciation that exposed the land bridge.
Such sites may have been home to populations that could have migrated to Chile by 12,500 years ago, according to Ted Goebel, associate director of Texas A&M University's Center for the Study of the First Americans in College Station.
Before the land bridge had become fully exposed, people might also have migrated from Asia by boat, Goebel says.
"There may have been enough land 14,000 years ago that people could have leapfrogged [by boat] from landmass to landmass," Holliday said.
They could walk across in the winter on the ice whether or not there was a land bridge.
They trudged through that pristine Alaskan wilderness, killed animals for food, cut timber for shelter, and burned wood for warmth. If it wasn't for their irresponsible exploitation of the environment and destruction of that fragile ecosystem, we may still be enjoying glaciers throughout the American midwest. Shameful.
/s
""There may have been enough land 14,000 years ago that people could have leapfrogged [by boat] from landmass to landmass," Holliday said."
So, now that we have that little problem out of the way...they could have come at anytime. Imagine that.
Maybe they were friggin born here. humans arrived in other places. Africa, Asia, why not here? Why did they have to come across anywwhere.
And who cares? Is it going to change who gets elected this year of sop the Palestinians from fighting?
..even more puzzling to researchers was a small structure on one side of the bridge that seemed to be filled with small objects, such as pelts and sharpened shells of minimal value.
"We believe that one tribe barred crossing crossing the bridge unless they received some gift," said one of the lead scientists.
Also found near the site were several petrified trees into which primitive man had carved crude pictographs. "From what we are able to discern, the pictographs are some kind of plea or demand. Roughly translated, they say 'Build the fence now.'"
Yeah! Thanks for putting that in perspective!
Seems to have been one mother of the whole race a long time ago. I read that somewhere.
"They could walk across in the winter on the ice whether or not there was a land bridge."
Doesn't sound too reasonable to me. Ice is cold, lack of fuel, lack of vitamin c sources would lead to scurvey.
And who cares? Is it going to change who gets elected this year of sop the Palestinians from fighting?"
He who does not remember the past is destined to repeat it!
Even now they go hunting way the heck out on the pack ice. While they use rifles and snowmachines these days, they are doing what they have always done. They could hunt all the way across from Siberia to Alaska, especially in winter, and camp anywhere they found land for the summer when it was more or less impossible to go anywhere.
At least two distinct groups of early humans colonized the Americas, a new study says, reviving the debate about who the first Americans were and when they arrived.
Anthropologists Walter Neves and Mark Hubbe studied 81 skulls of early humans from South America and found them to be different from both modern and ancient Native Americans.
The 7,500- to 11,000-year-old remains suggest that the oldest settlers of the Americas came from different genetic stock than more recent Native Americans. Modern Native Americans share traits with Mongoloid peoples of Mongolia, China, and Siberia, the researchers say.
But Neves and Hubbe found that dozens of skulls from Brazil appear much more similar to modern Australians, Melanesians, and Sub-Saharan Africans. Neves and Hubbe describe their findings in this week's edition of Proceedings of the National Academy of Sciences.
Who Was First?
The scientists examined 81 skulls unearthed over many decades in Brazil's Lagoa Santa region. They represent the largest collection of early American remains, many of which had to be tracked down in European museums.
These "paleoamerican" or "paleoindian" skulls feature projecting lower jaws, broad noses, and broad eye sockets, the researchers report. These traits are unlike those of modern Native Americans.
This strongly suggests that those early Americans were in fact a distinct group, Neves says.
He adds that the group could have crossed the Bering Strait land bridge—the once-exposed landmass between Siberia and Alaska—thousands of years earlier than the Siberian populations who are believed to be the ancestors of modern Native Americans.
Other paleoamerican skulls have displayed similar traits to the Lagoa Santa skulls, which has led to controversy and differing theories about how and when the Americas were settled.
"I don't want people to think that we are proposing any kind of transoceanic migration from Africa or Australia," said Neves, of the University of São Paolo in Brazil.
"We know that these [paleoindian] people had reached China around 20,000 years ago. The Mongoloid population that you see in [northeast] Asia today is more recent. So we don't have to think about transoceanic migrations to explain this."
Genetic Drift
Recent genetic studies of modern human populations have also suggested multiple early migrations across the Bering land bridge.
Neves and colleagues have not been able yet to extract ancient DNA from the Lagoa Santa remains—but excavations are yielding additional ancient remains.
"We have already found at least 20 new skeletons older than 8,000 years that are not part of our paper," he said.
Still, not all scientists are convinced that the variations found in the skulls are proof of multiple migrations to the Americas.
"There is a huge amount of variation among the first Americans, more than you see among any other population outside of the Pacific," said Joseph Powell, an anthropologist at the University of New Mexico in Albuquerque.
"Much of that is genetic, and it comes from the fact, I think, that these first Americans had very small colonizing populations, and they have a great degree of genetic variation due to genetic drift."
Genetic drift describes random variations in a group's genetic makeup. Small populations are especially prone to the phenomenon, because the genes of a single individual play a proportionately larger role in successive generations.
American Theories
For decades most scientists believed that the first Americans were a group of hunters, known as the Clovis people, who entered the Americas via the Bering land bridge some 11,000 to 12,000 years ago.
"I think it has become more widely accepted in the archaeological community that people were here prior to Clovis," said Michael Waters, director of the Center for the Study of First Americans at Texas A&M University in College Station.
Sites in Siberia have shown that people lived in the harsh region on the Asian of the land bridge as early as 27,000 years ago, he added.
"People could survive in that Arctic environment and survive quite well," Waters said. "There would be nothing to stop them from heading east into present-day Alaska."
Moreover, sites like Chile's Monte Verde, where tools have been dated to 12,500 years ago, have bolstered the theory that people were in the Americas before the Clovis period.
"If you look at the time periods when people could have come over by land, it must have been very late, just before Clovis, or prior to the ice sheets that formed over North America reaching their maximum extent around 20,000 years ago," Waters said.
Yet the land bridge theory no longer holds a scientific monopoly.
Some scholars favor coastal migration theories, in which early settlers hopped along the Pacific coast in boats.
More controversial theorists won't rule out the possibility of ocean crossings from Europe or Africa.
However those first Americans arrived, the remains they left behind may be the only clues that could someday tell their story.
This differs from Oppenheimer's map, which had Haplogroup B coming down the coast. That migration appears to have headed inland instead.
With the mtDNA studies now underway, things are changing quickly!
Does this mean that 'Native Americans' were immigrants...
just like the rest of us?
I guess the smarter immigrants prevailed.
Luzia
The second oldest skeleton ever found in the Americas.
The oldest human skeletonfound in the Americas is:
"With regard to the DNA testing, here is the story. Last year Dr. David Glenn Smith of U.C. Davis, an expert in extracting mitochondrial DNA from old bone, conducted the tests with two of his advanced graduate students. Restriction analysis of one of the samples initially indicated that the mitochondrial DNA of Arlington Springs Woman belonged to Haplogroup B (one of the five predominant clades of mitochondrial DNA lineages found among Native Americans). Dr. Smith and his team presented this result along with other tests of ancient skeletal remains from North America in a symposium at last year's American Anthropological Association meeting in San Francisco.
But if others had been here first, because what one group could have done with a boat, another group could have done as well, then that begs the question: What happened to them? One answer is that the Indian Conquistadors slaughtered them! Do the ancestors of conquerors deserve Federal cheese? Of course not! An equally possible answer is that the Indians simply intermarried with them and their descendants are still around to this day. But if you're a part of the Indian lobby, or that one political party that seems to get all of the support of dead voters, Indian or otherwise, then why take such a risk? Better to suppress such unfortunate information. This is why stories about what happened 20,000 year ago matter. Modern politics and modern political influence are bound up with such stories.
They came to do the work Aleuts won't do.
Professor Stephen Oppenheimer's Journey Of Mankind (The peopling Of The World)
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