3 January 2009
DNA tracks ancient Alaskan's descendants
An ancient mariner who died 10,000 years ago probably doesn't have any close relatives left in Alaska (USA). But some of them migrated south and their descendents can be found today in coastal Native American populations in California, Mexico, Ecuador, Chile and Argentina. That's some of what scientists learned this summer by examining the DNA of Tlingit, Haida and Tsimshian Indians in Southeast Alaska.
Working with elders at a cultural festival in Juneau, they interviewed more than 200 Native Alaskans who allowed them to swab tiny amounts of saliva from their cheeks to capture their mitochondrial DNA, the genetic material that's passed from mothers to children. Preliminary examination of those cell particles indicates that none of the participants possessed DNA similar to that extracted from On Your Knees Cave man, the 10,300-year-old Alaskan whose remains were discovered 12 years ago in a cavern on Prince of Wales Island. But some participants appear to be closely linked genetically to coastal Indian tribes in British Columbia and Washington state, in spite of anthropological studies that claim Tlingits were originally an Interior people.
Bones of the ancient Alaskan were first discovered in 1996 by Alaska paleontologist Tim Heaton during an archaeological survey on the northern tip of Prince of Wales island. Heaton's team recovered a male pelvis, three ribs, a few vertebrae and a toothy, broken jaw, along with some ancient tools. With the help of archaeologist E. James Dixon, they eventually pieced together the caveman's story. His teeth indicate he died in his early to mid-20s. The content of his bones revealed that his primary food came from the sea. The nearby stone tools, consisting of materials not found on the island, suggest a long-distance traveler, possibly a mariner.
Then the geneticists went to work. Washington State University Molecular Anthropologist Dr. Brian Kemp succeeded in extracting mitochondrial DNA from one of the caveman's teeth, the oldest DNA sample ever recovered in the Americas at the time. It clearly placed On Your Knees Cave man in the 'haplogroup-D' branch of the human family tree. That reduced the chances that he would have any close relatives still living among present-day Native Alaskans, Kemp said. The only known haplogroup D people in Alaska were the Aleuts. But that made them only distant relatives to On Your Knees Cave man - very distant, since scientists believe the D mutation appeared for the first time about 50,000 years ago in Asia.
On closer inspection, however, Kemp found that On Your Knees Cave man belonged more specifically to the genetic sub-group D4H3, which may have shown up as recently as 20,000 years ago. Still, it's an exclusive group. Less than 2 percent of all Native Americans share that signature. Aleuts living today don't appear to be that closely related to the caveman, Kemp said. Of the 163 tested so far, none were D4H3. According to Kemp's research, part of what happened in the Americas is this: Some of the caveman's relatives decided to head south from Alaska. Members of his specific genetic lineage have been found among the Chumash people of Southern California, the Cayapa of Ecuador and the Yaghan of Tierra del Fuego. The fact that most of them landed at seaside destinations lends a lot more credence to scientists who believe the Lower 48 states and South America were populated first by coastal mariners - Ice Age migrants from Asia who skirted around land-blocking glaciers in Alaska as early as 20,000 years ago
Did some of those first Alaskans remain behind in the North? In terms of present-day Native Alaskans who might share the same specific genetic marker as On Your Knees Cave man, the jury is still out, Kemp said. It's possible the right person with the right match simply hasn't been tested yet, said Rosita Worl, president of the Sealaska Heritage Institute, the nonprofit Southeast Alaska Native group that sponsored the research. It's also possible that the Tlingits and Haidas - migrating either from the south or the Interior - arrived in Southeast Alaska after the cave man's people had already passed through. Kemp is anxious to continue his research on his Tlingit DNA samples, to see if the matrilineal branches based on DNA match the matrilineal branches based on culture.
Sources: Capital City Weekly (24 December 2008), Anchorage Daily News (28 December 2008)