Cave divers find one of oldest human skeletons in N America

Cave divers have discovered one of the oldest human skeletons yet found in North America. Near perfectly preserved, the bones yielded DNA that has helped to answer questions about the earliest human colonisation of the New World.

Naia, as she was named by her discoverers, was perhaps 15 or 16 years old when she tumbled down a shaft into a cave system on Mexico's eastern Yucatán Peninsula at least 12,000 years ago. A cold, dark and inaccessible spot, she would have drowned in the deep pit - now called Hoyo Negro - before her remains settled into the water at the bottom of the cave, 40 metres below sea level.

There she lay undisturbed for thousands of years before being found by cave divers who were lowered into the pit to reveal its secrets. Details of the discovery and its importance are published this evening in the journal Science.

The skeleton was discovered in 2007 by exploration cave divers Alejandro Alvarez, Alberto (Beto) Nava Blank and Franco Attolini.*

The girl's skeleton was in near perfect order and "beautifully laid out", said Dr Patricia Beddows of Northwestern University in the US, who was part of an international research team led by the Mexican government's National Institute of Anthropology and History and with funding from the National Geographic Society.

Naia was not the only one to fall into the pit, surrounding her were the bones of saber-toothed cats and an early elephant-like animal the gomphothere. These proved valuable in helping the scientists to date Naia’s skeletal remains.

The skeleton was “exceptionally complete” because of the environment where she died. This also allowed the team to extract sufficient DNA from a tooth to examine her genetic code and help settle a long standing question over the human settlement of the Americas.

Modern Native Americans are thought to have descended from Siberians who migrated across a land bridge connecting what is now Russia and Alaska some time between 26,000 and 18,000 years ago, the researchers said. They would have continued migrating south to populate the continent, but there is disagreement.

Modern Native Americans physically don't look like the skeletons of these early migrants so a theory was proposed there were two distinct migrations with the second from a group related to Native Americans.

Naia looked like the earliest migrants but her DNA was able to reveal a different story. She has the look of the early migrants, but her genetic code showed that she was an early ancestor of modern Native Americans. The early migration brought in people who spread across the continent and down into what is now Mexico, with evolutionary changes accounting for the changing physical features of their modern ancestors.

*This article was edited on Friday, May 16th, 2014