Researchers working in northeastern Ethiopia have discovered remains of a previously unknown branch of humanity. The fossils, which include teeth that date to between 2.8 million and 2.6 million years ago, belong to a never-before-seen member of the genus Australopithecus—the same genus to which the famous Lucy fossil belongs. They show that this newly identified member of the human family lived alongside early representatives of our own genus, Homo. The findings were published in Nature on August 13.
The discovery team, led by investigators at Arizona State University, has yet to name the new species because the researchers need more fossils from other parts of the body to do so. But comparisons of the teeth with other fossils from the same site—Ledi-Geraru in the Afar Region of Ethiopia—as well as with other hominin fossils, revealed that they are distinctive enough to represent a species of Australopithecus that is new to science.
Together with previous finds, the new fossils demonstrate that at least four lineages of hominins (creatures more closely related to us than to our closest living relatives, the chimpanzees and bonobos) lived in eastern Africa between three million and 2.5 million years ago.
How these hominins were able to share the landscape is a question the team is working to answer. One possible explanation is that they preferred different foods. Studies of the enamel of their fossilized teeth may yield clues to what they were eating.
Once upon a time, scholars thought that human evolution was a march of progress in which our forebears evolved in linear fashion from an apelike ancestor to a series of increasingly humanlike forms. The new find underscores the complexity of human origins. Although Homo sapiens is the only hominin species on Earth today, for the vast majority of humanity’s existence, multiple hominin species shared the planet. Our family tree is more like a bush, with lots of twigs that were dead ends—failed evolutionary experiments that occurred outside of our direct line of ancestry.
