Chumash Indians could be their descendants

Feb 6, 2007 08:15 GMT  ·  By

The DNA analysis era has started making its steps on the realm of anthropological archaeology.

DNA extracted from a 10,300 years old tooth discovered in a cave on Prince of Wales Island (off southern Alaska) in 1996 points to a recent arrival of the humans in the Americas, about 15,000 years ago. The research revealed a new lineage for the people who first colonized the Americas and one explanation on how they could have spread.

The tooth's DNA was compared to that of 3,500 Native Americans, and matched with only 1 % of current Indians, living primarily on the Pacific coast of the Americas, from California to Tierra del Fuego, the southernmost tip of South America, discovery that points to an ancestral lineage of Indians spreading through the New World along the coasts. "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 molecular anthropologist Brian Kemp, a research associate at Vanderbilt University in Nashville, Tennessee.

The most accepted theory states that the first humans arriving to the Americas were hunters who crossed Behringia, a thousand-mile (1,600-kilometer) land bridge from Asia to Alaska, subsequently flooded when the Ice Age glaciers melted.

This colonization may have occurred at least 15,000 years ago and the oldest human fossils found till now in the Americas are 13,000 years old; however, some speculate that the first Americans reached the continents 40,000 years ago.

Kemp used fragments of mitochondrial DNA (mtDNA), which is always transmitted from mothers to their offspring, and Y chromosome DNA, which is transmitted from father to son. Out of the 3,500 Native Americans genotypes found in a database, only 47 individuals in North and South America, from living people or ancient bones, had the same genetic markers as the caveman.

Then, Kemp compared the tooth DNA with the matching modern DNA and assessed the mutations that had occurred over time. The rate of mutation (the speed at which genetic material changes over time) revealed a two to four times shorter molecular evolution of human populations isolated in the Americas than previously thought. "That 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", said Kemp.

Across all Native Americans, mtDNA lineages show five ancestral lineages thought to have originated in Asia. The new caveman DNA revealed itself as a new independent founding lineage. 4 of the 47 matching samples belong to descendants of Chumash Indians (image) inhabiting California's central coast before the arrival of the Europeans. "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."

"We're interested in who were those first people to arrive here at the Pacific coast. 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", said John Johnson, an archaeologist and ethnohistorian at the Santa Barbara Museum of Natural History in California.

DNA comparisons show some DNA mutation matched between the cave-tooth and Chumash people and people from Japan and northeast Asia. "I think that's a clue that there could be a genetic connection," Johnson said.

The Chumash ancestors could have been skilled fishers and seafarers before colonizing 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. I think that may have allowed a more rapid migration along the Pacific margins of the Americas", said Johnson.

Only DNA technology can solve some puzzles in human evolution and history. "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.