Prehistoric woman's remains found in underwater cave in Mexico

Feb. 6 (UPI) -- Paleontologists have unearthed the 10,000-year-old remains of a prehistoric human on southern Mexico's Yucatán Peninsula.

An international team of researchers determined the ancient bones belonged to a woman. Using a uranium-thorium dating technique, the scientists confirmed the woman lived during the late Pleistocene, at the very end of the last ice age.

"The new discovery emphasizes the importance of the Chan Hol cave and other systems in the Tulum area for understanding the early peopling of the Americas," researchers wrote in a paper describing their discovery, published this week in the journal PLOS One.

At the end of the last ice age, as glaciers melted, sea levels rose and flooded the Chan Hol cave system. Nine other prehistoric skeletons have been previously found in Chan Hol's intricate system of caves.

The ten skeletons recovered from the Chan Hol caves exhibit round-headed, or mesocephalic, cranial features, distinct from the long-headed, or dolicocephalic, characteristics of Paleoindians found in central Mexico and North America.

The difference in skull shape suggests Mexico was peopled by two morphologically distinct groups, possible hailing from two different geographical points of origin. It's also possible a small group of early Paleoindians split off from the first humans to arrive in Mexico and evolved unique cranial characteristics.

Analysis of the prehistoric woman's bones revealed the possible presence of a treponemal bacterial infection, which could have proved fatal. Researchers also found multiple injuries to the skull, but it's likely they happened postmortem.

Cavities in the woman's teeth suggest she at a diet high in sugar. Scientists have also previously found cavities in the teeth of other prehistoric humans found in the Chan Hol caves. In contrast, the worn, cavity-free teeth of Paleonindian previously recovered from central Mexico and North America suggest the group ate hard foods.

The differences in the teeth of the two sets of Paleoindian reinforces the theory that two morphologically distinct groups peopled Mexico during the the late Pleistocene and early Holocene.