WASHINGTON (AFP) - A teenage girl who fell into a hole more than 12,000 years ago in Mexico's Yucatan Peninsula is offering new clues about the origins of the first Native Americans, researchers said on Thursday.
Named "Naia" by scientists, her skeleton is among the oldest known and best preserved in the Americas.
She was discovered by a team led by the Mexican government's National Institute of Anthropology and History and supported by the Washington-based National Geographic Society.
Naia's remains were found in 2007, submerged in an underwater cave along with the bones of saber tooth tigers, giant sloths and cave bears, some 135 feet (41 metres) below sea level.
At the time she fell, some 12,000 to 13,000 years ago, the area, called Hoyo Negro, or Black Hole in Spanish, was dry and above ground.
Melting glaciers caused sea level rise that covered the pit with water for the last 8,000 years.
The girl was aged 15 to 16 and may have slipped into what appeared to her, and to the animals who met the same demise, to be a watering hole.
Her pelvis appears to have broken on impact, suggesting she died quickly after her fall, said Jim Chatters, an archeologist and forensic anthropologist in Bothell, Washington.
Her skull shows she had a small, narrow face, wide-set eyes, a prominent forehead and teeth that jutted outward.
Her appearance was "about the opposite of what Native Americans look like," Chatters told reporters.
But a genetic marker found in the girl's rib bone and tooth shows that her maternally inherited lineage was the same as that found in some modern Native Americans.
The report in the journal Science suggests she descended from people who migrated from Asia across the Bering Strait, over a land mass that was known as Beringia.
"What this study is presenting for the first time is the evidence that paleo-Americans with those distinctive features can also be directly tied to the same Beringian source population as contemporary Native Americans," said Deborah Bolnick, an assistant professor at the University of Texas at Austin.
That goes against theories held by some experts that Native Americans were descendants of people who migrated later, perhaps from Europe, southeast Asia or Australia.
"I used to be one of those advocates of multiple immigration events," said Chatters, an archeologist who is best known for his work on Kennewick Man, a 9,800-year-old skull and skeletal remains found in the US state of Washington.
Chatters initially believed that the Kennewick Man descended from European settlers, because his skull did not resemble a typical Native American face.
But subsequent research, including the DNA analysis on Naia, has changed his way of thinking about where the earliest Native Americans came from.
The international team of researchers working on Naia has identified just one genetic marker from her mitochondrial DNA, called mtDNA haplogroup D1.
"Haplogroup D1 is derived from an Asian lineage but is found only in the Americas today," explained Bolnick.
"Approximately 11 percent of Native Americans exhibit this genetic lineage," she added.
"It's found throughout North, Central and South America and this D1 lineage is especially common in some South American populations." Bolnick said their analysis at this point cannot exclude the possibility that other early peoples, known as paleo-Americans, came from places other than Beringia, but that so far the evidence does not support that possibility.
Naia is the sixth oldest human found in the Americas, said Chatters.
Future research aims to sequence her nuclear DNA, which should reveal more details about her ancestry.