Fossilized teeth show that two different kinds of ancient human ancestors coexisted more than 2 million years ago. One of them may be an unknown species.

Researchers have unearthed tooth fossils in Ethiopia dating to about 2.65 million years ago of a previously unknown species in the human evolutionary lineage, one that lived in the same time and place as the earliest-known member of the genus Homo to which our own species belongs.

Learn more about the handful of tooth fossils that complicate the history of humans in northeastern Ethiopia.