Underwater find in Mexico offers peek at genetic heritage of ancient Asian arrivals
Paul Nicklen/National Geographic
Support for a genetic connection between the first Americans and modern Native Americans has come from the submerged remains of a teenage girl who lived between 12,000 and 13,000 years ago in what’s now Mexico.
Divers discovered the youth’s partial skeleton, along with bones of more than two dozen large mammals, while exploring an underwater cave on Central America’s Yucatán Peninsula in 2007. An international scientific team led by archaeologist James Chatters of Applied Paleoscience, a consulting firm in Bothell, Wash., then joined forces with the divers.
As was true of previously unearthed skulls of early Americans, the girl’s facial features differ sharply from those of current Native Americans, the team reports in the May 16 Science. Yet the ancient youth shares with Native Americans a genetic profile that probably evolved among people who, between 26,000 and 18,000 years ago, occupied a land bridge connecting Asia to North America, say Chatters and colleagues.
“This is consistent with the hypothesis that Paleo-Americans and Native Americans derive from a single source population,” Chatters says.
Recent genetic findings, including DNA from an ancient baby’s skeleton found in Montana (SN: 3/22/14, p. 6), have pointed to a common genetic origin in Asia for Native Americans. DNA from the Mexican skeleton “confirms that there has been genetic continuity from ancient Americans to modern Native Americans,” says archaeologist and geologist Michael Waters of Texas A&M University in College Station, who studied the Montana baby’s remains.
Ancient American skulls, such as the new find and the skull of the more than 9,000-year-old Kennewick Man from Washington state, feature long, narrow brain cases and small, short faces, unlike those of modern Native Americans. Those signature looks raised the possibility that the first Americans and ancestors of Native Americans came from different Asian homelands and arrived in the New World separately.
An opportunity to test that hypothesis occurred in a submerged cavern that divers dubbed Hoyo Negro, or black hole. More than 40 meters, or 130 feet, below sea level, divers found 46 parts of a human skeleton — including a skull, 28 of 32 teeth, limb bones, a pelvis, spinal bones and ribs — scattered along the chamber’s floor. Bones of saber-toothed cats, giant ground sloths and other large animals, many of which had died out by 13,000 years ago, lay near the human remains.
Divers named the small female human skeleton Naia. She stood about 4 feet, 10 inches tall and died at age 15 or 16, based on bone and tooth development.
Naia and the animals found by divers probably fell to their deaths through a sinkhole into Hoyo Negro at a time when the cave was dry. Reconstructions of ancient climate and habitat changes suggest that rising seas submerged the coastal cave around 10,000 years ago.
Working with the scientific team, divers returned to Hoyo Negro to measure and digitally photograph its bone collection. A series of dives also retrieved Naia’s skull and several other bones, as well as a tooth from an extinct mastodon-like creature.
Radiocarbon dating of tooth enamel and chemical analyses of mineral deposits on bones indicated that Naia lived between 12,000 and 13,000 years ago. The extinct animals roamed the area much earlier, about 40,000 years ago.
One of Naia’s teeth yielded mitochondrial DNA, which is inherited solely from the mother. That DNA displayed an Asian-derived set of gene variants previously found only in North and South America. The study shows for the first time that members of this early maternal lineage reached Central America.
To pin down links between early New World settlers and modern Native Americans, DNA from mitochondria and cell nuclei of additional ancient Americans is needed, remarks archaeologist David Meltzer of Southern Methodist University in Dallas. Differences in skull shape between ancient and modern Americans with common genetic origins could have developed after a founding population split up and random genetic changes accumulated in separate groups, Meltzer says.
Naia’s ancient mitochondrial DNA lineage appears infrequently in native Mexican groups today, a sign that shifting and mixing of populations with different genetic characteristics have occurred since Naia’s time, comments biological anthropologist Theodore Schurr of the University of Pennsylvania in Philadelphia. Recurring migrations within the Americas, including forced resettlements of conquered peoples by pre-Columbian civilizations, helped to shape regional genetic profiles, he says.
Deep within the waters of Mexico's Yucatan Peninsula is a cavern called Hoyo Negro. It holds a collection of bones from ancient saber tooth cats, giant ground sloths, mammoths and even a young girl. The human remains show the genetic range of the continent's ancient Asian colonists. Produced by: Ashley Yeager
J.C. Chatters et al. Late Pleistocene human skeleton and mtDNA link Paleoamericans and modern Native Americans. Science. Vol. 344, May 16, 2014, p. 750. doi:10.1126/science.1252619.
T.H. Saey. Clovis baby’s genome unveils Native American ancestry. Science News. Vol. 185, March 22, 2014, p. 6.
Center for the Study of the First Americans website