Around 12,000 years ago, a teenage girl fell 190 feet into a deep pit in the Yucatan Peninsula, breaking her pelvis. The fall killed her instantly, and over time, the pit became a watery tomb as glaciers melted and sea levels rose. Her body remained hidden until 2007 when cave divers happened upon her preserved remains. At the time, they did not know they had discovered the most genetically intact human skeleton in the New World—capable of answer the question: Who were the first Americans, really?
It has long been suspected that all Native Americans are descendants of ancient Siberians who moved across the Beringia land bridge between Asia and North America between 26,000 and 18,000 years ago. Over decades and centuries, these people spread southward and gave rise to the Native America populations Europeans settlers encountered when they discovered America. But there is a puzzling problem with this theory.
“Modern Native Americans closely resemble people of China, Korea, and Japan…but the oldest American skeletons do now,” archeologist and paleontologist James Chatters told Smithsonian. In fact, early American specimens have smaller and shorter faces and longer skulls than later Native Americans—more closely resembling the modern people of Africa and Australia.
“This has led to speculation that perhaps the first Americans and Native Americans came from different homelands or migrated from Asia at different stages in their evolution,” Chatters continued.
The discovery of Naia will help to resolve the debate. Her remains revealed a skull that is shaped like those of other early Americans, but her DNA revealed a sequence present in modern Native Americans. Essentially, she is probably a great-aunt to the indigenous people currently found in the Americas.
To determine Naia’s age, researchers studied regional sea-level data to get a minimum age at which the cave filled with seawater. Studies revealed that Naia would have become submerged between 9,700 and 10,200 years ago—meaning Naia would have had to fall into the cave before then. When researchers radiocarbon-dated her tooth enamel, they determined she was around 12.900 years ago.
Her teeth also played another significant role; scientists were able to extract DNA from her molars. Researchers focused on mitochondrial DNA (mtDNA) which is used by geneticists to examine how populations are related. More specifically, researchers focused on haplotypes or sequences of genes that are slower to mutate. Their analysis revealed a haplotype that occurs in modern Native Americans—which scientists believe evolved in Beringia.
“We were able to identify her genetic lineage with high certainty,” Ripan Malhi, a professor of anthropology at the University of Illinois notes. “This shows that living Native Americans and these ancient remains of the girl we analyzed all came from the same source population during the initial peopling of the Americas.”
Scientists are now able to confirm that migrations from Beringia made it to southern Mexico. Not all questions are answered, however. The fact that Naia is the genetic forerunner to modern Native Americans raises speculation about whether scientists will be able to get access to earlier Americans yet to be uncovered.
Source: Smithsonian Magazine