The polar ice caps melted dramatically 8,000 to 9,000 years ago, causing sea levels to rise hundreds of feet and submerging the burial grounds of the skeletons.
"When we learn more about the [Mexican finds] we'll be able to better evaluate them," said Carlos Lorenzo, a researcher at the Universitat Rovira i Virgili in Tarragona, Spain, an expert on the subject who was not involved in the current study.
"But in any case, if it's confirmed that Eva de Naharon is 13,000 years old, it will be a fantastic and extraordinary finding for understanding the first settlers of America." González said he and his team hope to publish the full results of their analysis after the excavation of the fourth skeleton.
This chart shows the percentage of radiocarbon that remains in 40 samples from various layers throughout the geologic column.
(This percentage, technically known as percent modern carbon [p MC], shows the ratio of radiocarbon in the rocks and fossils compared to the amount we find in living things).
It is literally able to count carbon-14 atoms one at a time.3 This machine can theoretically detect one radioactive carbon-14 atom in 100 quadrillion regular carbon-12 atoms! AMS instruments need to be checked occasionally, to make sure they aren’t also “reading” any laboratory contamination, called background.