To find the first Americans, search below the sea

We still don't know how humans got to the Americas. Many researchers are arguing we need to ditch the land-first hypothesis of human migration, and look for underwater evidence of a seafaring past. It's an idea that's gaining momentum, though the evidence is complex and the proposal isn't unanimously accepted.

Data: Sites compiled from academic papers & information provided by Braje; Map: Lazaro Gamio / Axios

This map shows some of the oldest archaeological sites in the Americas. Many in South America are either along the coastline or major waterways, supporting the coastal migration hypothesis. But North America looks a lot messier and lacks coastal sites.

Why it matters: "We're trying to answer one of the most fundamentally important questions in American archaeology," Todd Braje, an author of the paper that appears today in Science, tells Axios. Recent finds have challenged the old, accepted models of a single migration over a single route.