The First American Teenager, Millennia-Old And Underwater

DNA from the skeleton of a 12,000-year-old teenage girl found on Mexico's Yucatan Peninsula shows that today's Native Americans are descended from Siberians who spread southward across North America.

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TESS VIGELAND, HOST:

From the studios of NPR West in Culver City, California it's ALL THINGS CONSIDERED. I'M Tess Vigeland. Let us contemplate the American teenage girl, perhaps the very first one. Apparently, there's been some scientific debate about who she is and whether she hails from the same gene sequence as what we think of as the first Americans, American Indians. And when I say gene sequence, we're not talking about Skinnies from Urban Outfitters. NPR's science correspondent Joe Palca has the story of a very old American teenage identity crisis.

JOE PALCA, BYLINE: A few years ago, archaeologist and paleontologist James Chatters was at a scientific meeting when a colleague showed him a picture. It was taken by divers at the bottom of a cave on the Yucatan Peninsula. The cave had flooded sometime in the last 12,000 years or so. In the picture there was a human skull.

JAMES CHATTERS: I could tell from the shape of the palate and some other aspects of the skull that she was similar to the other earliest Americans I'd seen.

PALCA: Along with a variety of colleagues from around the United States and Mexico, Chatters began an intensive investigation of the girl's skull and other bones. The first fruits of their labors appeared in the journal Science. They estimate the girl was 15 or 16 years old when she died and that she'd been dead for between 12 and 13,000 years.

But it's the girl's DNA that proved most intriguing. That's because there's been a big debate about whether modern Native Americans are related to the very first people who came to the Americas, like the young girl, or to people who came in a more recent migration. The reason there's a question about that is the first people who came to the Americas, like this young girl, don't look very much like modern Native Americans. Chatters says modern Native Americans have narrower faces, different teeth, different palate.

CHATTERS: So many differences that it seemed like they must come from somewhere else.

PALCA: But the girl's DNA tells a different story. Deborah Bolnick is from the University of Texas Austin. She's an expert in extracting ancient DNA from fossilized teeth and bones.

DEBORAH BOLNICK: A lot of my work is focused on trying to use genetics to help us understand more recent population history in the Americas.

PALCA: Bolnick studied the girl's mitochondrial DNA, a type of DNA you inherit exclusively from your mother. What she found was the girl had a mitochondrial DNA inheritance pattern that's quite common in Native Americans alive today. So despite the differences in appearance, Bolnick says the new results suggest that modern Native Americans are indeed descended from the very first humans to reach the Americas, and not some more recent migration.

By studying more of the girl's DNA, scientists are hoping to get clues about which genes were responsible for the changes in appearance. Joe Palca, NPR News.

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