10,000 year-old TOOTH has Native American history -
AmericanIndianDNA.com
- - -
Brian Kemp learned a lot from one 10,300-year-old tooth.
The Washington State University researcher identified a previously
unknown pattern of relationships among Native Americans - suggesting
that humans arrived here more recently than previously believed and
migrated down the western coastlines from Alaska to the tip of South
America. His finding suggests that ancient teeth might become a wider
source for discovering historical DNA and unlocking more information
about the past.
"We learned something that we would have never known and it's
important now that we start studying teeth," said Kemp, a molecular
anthropologist who did the research as part of a team while finishing
his doctoral work at the University of California, Davis.
Kemp's research on the tooth discovered in Alaska's On Your Knees Cave
was dubbed one of the top 100 science stories of 2007 by Discover
magazine. It was the oldest human genetic sample from the Americas
ever analyzed, an extreme rarity because most DNA doesn't survive a
few hundred years, let alone thousands.
"Ten thousand years is a long time and that's why the sample is so
important," Kemp said. "I've worked on 500-year-old samples that have
no DNA."
He was one of two WSU researchers on the Discover list. The other was
Michael Skinner, who made the Top 100 once before for research showing
that when pregnant mammals were exposed to a common fungicide, their
descendants suffered disease and other health effects for several
generations. That one-time exposure creates "epigenetic" additions to
the DNA of the exposed mammal and its descendents.
Most recently, Skinner has shown that the male descendants of rats
exposed to toxins become less attractive to females even if they're
not sick - meaning that pollution can affect not only the DNA of a
family for generations, but the overall development of a species,
Skinner said in a news release.
"This is one of the first experimental studies to support a role for
epigenetics in evolutionary biology," he said. "We showed that
epigenetic changes can modify sexual selection in such a way as to
influence the evolution of a species."
Kemp, who started working at WSU in the fall, has done a lot of work
searching for DNA in skeletal remains - including analyzing bones from
apparent mass Aztec sacrifices. As part of the team at UC-Davis, he'd
looked for DNA in other bones found in On Your Knees Cave in 1996, but
hadn't found any genetic material.
But when he tested a tooth, "it worked and it worked amazingly," he
said.
Discover called the find "genetic gold."
It's not entirely clear why fragments of DNA survive in some bones and
not others. Having a steadily cool and dry environment, like a cave,
helps.
When Kemp looked at the sequence of DNA from the sample, he found a
pattern of mutations that matched one of five known genetic types
associated with Native Americans. But he also found another pattern of
mutations that he'd never seen before. When he compared it with all
the other samples of Native American genetic material available, he
found the pattern in about 1.5 percent of the samples.
Most of those samples had come from coastal areas, from Alaska all the
way down to Tierra del Fuego, at the tip of South America. The
analysis of the DNA also suggested that people had first arrived in
the Americas much more recently than previously believed - about
15,000 years ago instead of 40,000 - and migrated south along the
coast. Among those samples, the relationship between people living in
Alaska and Peru, for example, was closer than that between coastal and
inland Native Americans.
Kemp said that makes sense, given that the skills necessary for
coastal living would be similar even in different parts of the world.
"If you know how to live on the coast in Alaska, you know how to live
on the coast in Mexico," he said.
Kemp said that the discovery suggests the possibility that teeth could
be good sources of ancient DNA. That's important because other methods
of archeological research couldn't have turned this up, he said -
studying artifacts would not suggest the extent of the relationship or
migration. But teeth are highly prized by scientists in a lot of
fields, because they reveal information about peoples' growth and
habits, and it's sometimes difficult to get them for DNA testing,
which is destructive.
As part of his research, Kemp looks for DNA in other places, too.
Another good source of very old genetic material is desiccated fecal
matter preserved in caves.
"I'm at work on a number of really old fecal samples right now," he
said.
Walt
http://AmericanIndianDNA.com
.
,