for National Geographic News
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.
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