Above; Divers use lights to illuminate the underwater cave where a 12,000- to 13,000-year-old skeleton was found. Photo: Roberto Chavez Arce, Associated Press
David Perlman
May 14, 2014
A lithe young girl - perhaps in search of water to drink - fell to her death inside a dry cave in Mexico more than 12,000 years ago at the end of the last Ice Age.
Seven years ago, a 47-year-old diver from Monterey discovered the teenager's skeleton while exploring a deep underwater cave on the Yucatan Peninsula with two Mexican friends.
It was a provocative discovery, and now the girl has become a legacy for archaeologists pondering the origins of today's Native Americans.
More than a dozen scientists reported Thursday that the teenager's unbroken skull and her nearly complete skeleton show the clearest evidence yet that she carried the same genetic heritage that has marked the original people of the American continent.
The divers had named the girl Naia, Greek for water nymph.
The scientists say she and her modern relatives are all descendants of far earlier humans who had migrated between 26,000 and 18,000 years ago from East Asia to America across a land mass known as Beringia, which is now beneath the Bering Sea.
The accounts of Naia's genetic legacy and the techniques that determined the geologic epoch of her death were published Thursday in the journal Science on Thursday.
Unique time capsule
Her discovery, said James C. Chatters, an anthropologist and leader of the research team, has provided the first unique "time capsule of the environment and human life at the end of the Ice Age."
He said in a news conference that in Naia's time the cave where she died was one of many that were once "dry and accessible" because the massive glaciers of the Ice Age were still holding back the world's oceans. Now those caves are flooded and filled with water.
The report in Science described how the scientists isolated genetic material from Naia's teeth to determine a clear link between her maternal lineage - marked by her mitochondrial DNA - and modern Native Americans.
The girl's skull formation shows that her face would have looked very different from today's Native Americans, indicating an evolutionary process that had altered the faces of Native Americans over the thousands of years since Naia lived.
Chatters is well known for his detailed study of the famed Kennewick Man, a 9,000-year-old partial skeleton unearthed along the Columbia River in Washington in 1996. Its features had once led Chatters to believe that some ancient people in the Americas "might represent an earlier migration from a different part of the world, perhaps from Southeast Asia or even Europe."
The genetic evidence of Naia and her antiquity has changed his mind, he said.
Left: Divers Alberto Nava and Susan Bird hold an Ice Age skull found in an underwater cave in Mexico's Yucatan Peninsula. Photo: Paul Nicklen, Associated Press
Cave discovery
Alberto Nava, the California cave diver who found her skeleton, said he is creating a nonprofit institute to explore for other evidence of Ice Age people in the area where she was found.
Nava, a leader of the 60-member Bay Area Underwater Explorers in Berkeley, said he and his Mexican dive buddies, Alex Alvarez and Franco Atollini, discovered the bell-shaped cave, at least 200 feet in diameter, deep in the Yucatan jungle in 2007 while feeling their way underwater in the dark through a sunken rock corridor.
They returned to the chamber two months later and, using brilliant underwater lights, spotted Naia's skull and a human leg bone resting on a ledge. "She had a perfect set of teeth and dark eye sockets looking back at us," he recalled.
Nearby were the bones of long-extinct animals - sabertooth tigers, huge ground sloths, a primitive elephant and many other creatures.
They named the chamber Hoyo Negro - for Black Hole - and kept their find secret for more than two years to protect it before notifying Mexican authorities, Nava said. Then the science began.
"Very few of the researchers scuba dive, and none of them go deep in caves," Nava said, so they began recovering material for the scientists.
"They explained what they wanted us to do, they trained us to do it and then we conducted most of the tasks underwater," he said.
The divers brought up human and animal bones for study, chipped away rocks for dating and extracted sediment cores for analysis. They mapped the chamber, surveyed the entire site, and took photos and videos for the scientists.
"We're their hands and eyes," Nava said.
David Perlman is The San Francisco Chronicle's science editor.
E-mail:dperlman@sfchronicle.com
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