Using samples of ancient and modern mitochondrial DNA—which is passed down only from mothers to daughters—the researchers calculated a demographic history for American Indians. (Get an overview of human genetics.)
Based on the data, the team estimates that the Native American population was at an all-time high about 5,000 years ago.
The population then reached a low point about 500 years ago—only a few years after Christopher Columbus arrived in the New World and before extensive European colonization began.
Story: Ker Than, National Geographic News | Photo: Richard Schlecht, National Geographic