Posted on 02/02/2007 4:52:13 PM PST by blam
First Americans Arrived Recently, Settled Pacific Coast, DNA Study Says
Stefan Lovgren
for National Geographic News
February 2, 2007
A study of the oldest known sample of human DNA in the Americas suggests that humans arrived in the New World relatively recently, around 15,000 years ago.
The DNA was extracted from a 10,300-year-old tooth found in a cave on Prince of Wales Island off southern Alaska in 1996.
The sample represents a previously unknown lineage for the people who first arrived in the Americas.
The findings, published last week in the American Journal of Physical Anthropology, shed light on how the descendants of the Alaskan caveman might have spread.
Comparing the DNA found in the tooth with that sampled from 3,500 Native Americans, researchers discovered that only one percent of modern tribal members have genetic patterns that matched the prehistoric sample.
Those who did lived primarily on the Pacific coast of North and South America, from California to Tierra del Fuego at the southernmost tip of South America (see map).
This suggests that the first Americans may have spread through the New World along a coastal route.
Brian Kemp, a molecular anthropologist who sequenced the DNA, said the discovery underlines the importance of genetic research in understanding human migration.
"I think there's a lot of information in these old skeletons that's going to help us clarify the timing of the peopling of the Americas and perhaps where Native Americans originated in Asia," said Kemp, a Ph.D. candidate at Vanderbilt University in Nashville, Tennessee.
On Your Knees Cave
When and how the first people came to the Americas has been a subject of intense debate.
The prevailing theory has been that the first to arrive descended from prehistoric hunters who walked across a thousand-mile (1,600-kilometer) land bridge from Asia to Alaska. This migration probably occurred at least 15,000 years ago—the oldest human remains discovered so far are 13,000 years old—but some scientists have proposed that the first Americans arrived up to 40,000 years ago.
The Alaskan tooth was discovered in a cavern called On Your Knees Cave, named by the explorer who first crawled inside it.
Using material taken from the tooth, Kemp isolated fragments of mitochondrial DNA (mtDNA), which is passed down from mothers to their offspring, and Y chromosome DNA, which is passed from father to son.
From a genetic database of 3,500 Native Americans, Kemp found 47 individuals in North and South America who exhibited the same genetic markers as the caveman. Some of the samples were drawn from living people and others from ancient bones.
He then compared the tooth DNA with the matching, modern samples and tracked the mutations that had occurred in that DNA over time.
By measuring the rate of mutation, Kemp found that so-called molecular evolution—the process by which genetic material changes over time—had taken place two to four times faster than researchers believed mtDNA could evolve.
That, Kemp said, suggests people entered the Americas within the last 15,000 years, because the DNA has evolved too fast for the arrival to have occurred any earlier.
"I would say that humans were probably not here much before that date," said Kemp. "A 15,000-year-old entry is [also] much more consistent with the archaeological record."
Genetic Markers
All of the mtDNA lineages among Native Americans are associated with five founding lineages believed to have originated in Asia.
But the caveman DNA turned out to be an independent founding lineage.
Of the 47 samples that matched the tooth DNA, 4 were from descendants of Chumash Indians living along California's central coast.
"The distribution of people exhibiting this [genetic] type today are all distributed in the western Americas," Kemp said.
"More or less the individuals are smack down the coast. It's a very neat western distribution."
John Johnson, an archaeologist and ethnohistorian at the Santa Barbara Museum of Natural History in California, collected the Chumash DNA samples.
To Johnson, the matching of the Chumash samples to the On Your Knees Cave man is indirect evidence of an ancient coastal migration that may have occurred very rapidly.
"We're interested in who were those first people to arrive here at the Pacific coast," Johnson said.
"I believe the Chumash descended from a very early coastal migration that resulted in the distribution of people down to the tip of South America."
Fishing Cultures?
But where did these coastal migrants come from?
DNA samples of people living in Japan and northeast Asia show some of the genetic mutations found in the cave-tooth and Chumash samples.
"I think that's a clue that there could be a genetic connection," Johnson said.
He said the Chumash descendants may have been skilled fishers before they arrived in the Americas.
"Your techniques for exploiting coastal resources are easily [transferable] and something that maybe can allow you to migrate more quickly than people who are hunters and gatherers, who must get used to new environments as they move into uncharted territory," Johnson said.
"I think that may have allowed a more rapid migration along the Pacific margins of the Americas."
Kemp, meanwhile, said rapidly advancing DNA technology will help scientists piece together the story of the first Americans.
"No expert in morphology could look at the bones and say this person resembles a Tierra del Fuego person. It was only the DNA that could seal the case," Kemp said.
"This really highlights the importance of adding a molecular component to the study of these really ancient remains."
So where did these people go and where did the modern tribes come from? They weren't related, it seems.
So where did these people go and where did the modern tribes come from? They weren't related, it seems.
The old mtDNA pattern is still there, but it has been partially or mostly swamped out by more recent or more numerous arrivals.
There were probably two or more early coastal migrations, bringing at least haplogroups D and A. Another form of D, along with B and C, seem to have come later.
The second D, along with B and C, may have come via the land bridge through central Canada. They had an adaptation which let them spread rapidly in terrestrial habitats, while the coastal dwellers had an adaptation which kept them close to the coast.
The National Geographic DNA map I linked in post #10 show the following DNA groups in the Americas = A, B, C, D, M3, M217 and X.
The west coast, where I work, does not have any real number of X, and haplogroup M is a quite recent discovery in British Columbia (just last year). It certainly is not yet understood.
I think the map is misleading because 1) there are two different D lineages (based on recent discoveries). One is coastal the other probably interior. And 2) the A seems to have been coastal.
The NG map, and Oppenheimer's as well, jumble them all together. But that's to be expected, as the discoveries are coming very quickly now.
Maybe.
I just figure these maps/publications are for the general population like me, without the finer details and not for experts like you. LOL, I work at this and I can't keep things straight. So...
Its more that things are changing so fast that the popular websites can't keep up.
These mtDNA studies are only 10-15 years old, and the data is coming in very rapidly now. There is no way to keep up with it all, even though we all try.
better a tooth than a pile of processed forage...
Bison Poop Reveals Two Distinct U.S. Populations
[ Holy Feces!!! ]
LiveScience | January 30, 2007 | Jeanna Bryner
Posted on 02/02/2007 12:39:53 AM EST by SunkenCiv
http://www.freerepublic.com/focus/f-chat/1777824/posts
Please FREEPMAIL me if you want on or off the
"Gods, Graves, Glyphs" PING list or GGG weekly digest
-- Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
Gods, Graves, Glyphs (alpha order)
Ahem, in polite company, we say coprolite. (So, it's not necessary around here)
What about in coprolite company? ;')
I hope they made *denture* this mtDNA sample wasn't contaminated, and was *molar* less pristine.
YEC INTREP
"My calibration shows that the changes (mutations) were occurring two to four times faster than previously thought,"...people have overestimated the time. It wasn't so long ago." (and) previous DNA data flawed..."I hope the impact of my paper will be to bring the molecular timing more in line with the archaeological record," he says. "This is what you want your work to do."
Means that the author is bending one factor, statistical norms for mutation, in order to accomodate another, accepted interpretations of a time line.
What accounts for the 'two to four times greater' rate of mutation?
Thisparticular Early American arrived maybe 15k years ago. They can't stanch the leakout by generalizing an admitted 15k years.
And from the article fromwhich blam bolded the following sentence:
Comparing the DNA found in the tooth with that sampled from 3,500 Native Americans, researchers discovered that only one percent of modern tribal members have genetic patterns that matched the prehistoric sample.
You are not missing anything--you are correct, a point that the writer of the piece either did not understand or left out purposefully.
There were several peopling events that occurred in North and South America. This data shows one that happened 15k years ago--no more, no less.
And thanks for posting, blam, and thanks for the ping, SC.
Dessicated even.
Thanks for the nice synopsis!
"not enough data to be conclusive"
I think there is a lot of pressure to say something bold on every find. I've had similar feelings on recent other news releases including the Terror Bird not living alongside humans (Florida). They only showed me where that particular find of the Terror Bird did not live alongside humans. I don't think they should extrapolate that much without adding a caveat. Maybe the news publishers want the boldness of statement to make the articles more interesting and eye catching.
I read interesting or bold statement articles so I guess the idea works.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.