First Americans Arrived Recently, Settled Pacific Coast, DNA Study Says

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Jack Linthicum - 11 Feb 2007 15:59 GMT

The oldest human bones found in a North American site belonged to
Arlington Man (actually woman) found on Santa Rosa Island and dated to
13,000 ybp. The Channel Islands are an area of Chumash occupation.

News Front Page > The Genographic Project
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 online 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
research associate 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.

(See a map of human migration.)https://www3.nationalgeographic.com/
genographic/atlas.html

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 ancestors 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."

http://news.nationalgeographic.com/news/2007/02/070202-human-migration.html?sour
ce=rss

History Forum / General / Archaeology / February 2007

First Americans Arrived Recently, Settled Pacific Coast, DNA Study Says