Oldest American genetic sample reveals early New World frontiers.
The oldest sample of human DNA ever isolated in the Americas is providing a glimpse of how people spread across the land masses.
The DNA was extracted from teeth, more than 10,000 years old, found in a cave on the northern tip of Prince of Wales Island, off southern Alaska. Researchers compared the pattern of mutations in the DNA against those in thousands of samples. They found matches with 47 Native Americans from tribes living in areas ranging from North America to Tierra del Fuego, showing how the caveman's descendants must have spread.
“I could hardly believe what I found,” says molecular anthropologist Brian Kemp from the University of California, Davis, who reported the results last month at a regional meeting of the American Association for the Advancement of Science in Ashland, Oregon.
The work, which has yet to undergo peer review, indicates how genetic techniques are giving researchers a new window on genetic migration, says Kemp. Cooperation between scientists and Native American tribes on the project is cited as an example of how science and traditional cultures can coexist — in stark contrast to the case of Kennewick man, bitterly disputed for nine years before studies finally began last month (see Nature 436, 10; 200510.1038/436010b).
The DNA was extracted from teeth on a mandible found in 1996 in On Your Knees Cave, named by the explorer who first crawled inside in 1993. Carbon dating in 1997 showed the remains to be from someone living 10,300 years ago. Attempts to extract DNA from the bone failed, so Kemp spent two years probing the teeth. Working in high-containment facilities to prevent contamination, he and his colleagues finally managed to isolate fragments of mitochondrial DNA, which is passed down the maternal line, and Y chromosome DNA, which is passed from father to son.
The researchers compared the mitochondrial DNA with nearly 3,500 Native American sequences available in public databases. They found 47 matches, mostly from modern individuals but some from samples up to 1,500 years old. More than half of the matches were with members of the the Cayapa coastal tribe in Ecuador. Others were with members of the Chumash tribe of California, the Klunk Mound people in Illinois, the Tarahumara of Chihuahua in Mexico and the Mapuche and Yaghan tribes of Chile.
The caveman belonged to ‘lineage D’, one of the five founding lineages believed to have settled in the Americas more than 10,000 years ago. Lineage D is thought to have originated in Asia, and researchers also found a close match with a member of the Han ethnic group from Qingdao in eastern China.
“This is an exciting frontier,” says co-author James Dixon, an archaeologist at the University of Colorado, Boulder, who first dated the remains. But he adds that it will be important to repeat the work with other samples.
The local Tlingit and Haida tribes welcomed the project, which supports their concept of ‘haa shagoon’, learning from their ancestors.
“We went right to the tribes within 24 hours of finding the bones, asking them to be a partner,” says Terence Fifield, the US Forest Service archaeologist for the region.
“We viewed the remains as offering us knowledge,” says Rosita Worl, a Tlingit tribal member who is a Harvard-trained cultural anthropologist. “We wanted the knowledge for current and future generations.”
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Biological Conservation (2006)