AUDIE CORNISH, HOST:
One day, about 12,000 years ago, a girl was walking around in cave. This was on the Yucatan Peninsula in what we now know as Mexico. She fell into a deep pit, fractured several bones in her pelvis and died. Today, that cave is underwater but the girl's remains were found by divers. And now her DNA is helping scientists understand where the earliest Americans came from.
NPR science correspondent Joe Palca has the story.
JOE PALCA, BYLINE: A few years ago, archeologist 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 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 palette 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 appear in today's edition of 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 palette
CHATTERS: Oh, so many differences, that it seem like they must come from somewhere else.
PALCA: But 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 using 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 suggests 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, Washington.
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