Ancient Skulls of Early Settlers in North America Baffle Scientists: 'We Still Have a Lot to Learn'

Scans of ancient human skulls found in Mexico show that the early residents of North America were a more diverse lot than previously thought.

The findings challenge accepted wisdom that assumed migration at the north end of the continent mimicked that in the south.

"We always assumed that what was happening in South America was true in North America. Now we need to revise that," co-author Mark Hubbe, Professor of Anthropology at The Ohio State University, said in a statement.

"We need to stop talking about the settlement of the Americas. We should talk about the settlement of North America and the settlement of South America as very different."

Researchers have analyzed four skulls between 9,000 and 13,000 years old, found recently in the state of Quintana Roo in Yucatan, Mexico. The results have been published in the journal Plos One.

Hubbe and colleagues scanned skulls (or, in some cases, the remains of skulls) for specific landmarks to determine their relation to different ethnic groups. These landmarks were mapped onto a 3D grid and compared to those of reference populations from across the world.

This stands in stark contrast to previous research, which suggested the first people to arrive in the Americas were a relatively homogenous group. This earlier research is largely based on remains from South America, suggesting two different paths of migration between the north and the south.

One skull, for example, identified as Naharón, is thought to have belonged to a woman who was a young adult when she died. Her's most closely resembles Arctic populations in North America, from what is now Greenland and Alaska. In contrast, another identified as El Pit I—a male believed to have died in the early stages of adulthood—showed signs of European heritage.

The third (Las Palmas), showed signs similar to Native American and Asian groups, including populations from Japan. Meanwhile, the fourth (Muknal) displayed markers akin to arctic and South American populations.

While the results suggest the origins of these settlers may be more complex than originally thought, the study's authors do urge some caution when it comes to interpreting the results.

Deterioration of the skulls can limit the number of landmarks identified and thus, the accuracy of the final results. The researchers point to Naharón and El Pit I in particular, both of which were less complete than the other two skulls.

Despite these limitations, the study suggests these initial settlers in North America were more biologically diverse than previously thought, and more so than those that settled in South America.

"The first Americans were much more complex, much more diverse than we thought," Hubbe said.

"We have always talked about the settlement of the Americas as if North America and South America were the same. But they are different continents with different stories of how they were settled."

In sum: "Whatever we thought about the settlement of the Americas is probably not the whole story. We still have a lot to learn."

Ancient Skull
Researchers have analyzed four skulls between 9,000 and 13,000 years old, finding the early settlers of North American were more diverse than previously thought. Picture: An ancient skull not involved in the study. Corbis/Getty