Researchers have accurately determined the age of the oldest-known, well-preserved human skeleton.
Her ancestors' origins were in Beringia, an area once above water between Siberia and North America. The D1 haplotype likely developed after early humans moved into the area from elsewhere in Asia. The physical differences between Paleoamericans and Native Americans, likely resulted from in situ evolution rather than having a separate ancestry.
The skeleton of this young woman, Naia, was buried underwater in an elaborate cave system in the Yucatan Peninsula after she had apparently fallen into what was then a dry deep pit.
The refined sea-level curve showed that the site, now 42 meters under water, would have become submerged during sea level rise between 9,700 and 10,200 years ago, long after Naia and the other extinct animals likely fell into it.
Naia's skull shape does not look like those of Native Americans, but the Beringian-derived mitochondrial DNA (mtDNA) D1 haplogroup (D1) directly links her to the modern Native peoples of the Americas.
To unravel the mystery of Naia's age, Professor Yemane Asmerom and Research Scientist Victor Polyak at the University of New Mexico's Department of Earth and Planetary Sciences, first conducted uranium-thorium dating of one of her teeth, and while those first results were promising, they were inconclusive. However, more clues were left behind in the cave.
Mineral deposits in water dripping from the roof of the limestone cave splashed onto the cave floor, and mist from those drip water impacts formed delicate rosette-looking speleothems (cave formations) that the divers called 'florets.' It turned out the average of the tooth data also converged to the age obtained from the mineral deposit data.
Having perfected this method of speleothem chronology with near pinpoint accuracy in previous research over the years in their state-of-the-art Radiogenic Isotope Laboratory at UNM that Asmerom leads, they were equipped to date the delicate florets that adhered to the top of Naia's body after she fell in the cave. The radiocarbon dating of the DNA tooth enamel yielded a maximum age for Naia of 12,900 years ago, while UNM's uranium-thorium results provided a minimum age of 12,000 years ago, confirming that Naia was a Paleoamerican.
The research has been published in the journal Science.
