The story of the First Americans — who they were, and when and how they dispersed across the New World — remains one of the most debated chapters in the human story.
Archaeologists, geologists and geneticists, among others, have weighed in with different scenarios. But, so far, only one thing is certain: We've got a lot left to learn.
"Talking about the settlement of the Americas is like building a 1,000-piece jigsaw puzzle with only about 20 pieces," says Ohio State University anthropologist Mark Hubbe. "Which means we need to pick up crayons and make our own drawings to complete the gaps between pieces."
Hubbe and colleagues analyzed four of the oldest human skulls found in North America, collected from 2008 to 2015 from underwater caves and sinkholes in the Mexican state of Quintana Roo, just a few miles from popular tourist sites such as the Mayan ruins of Tulum.
