Fossil find adds a relative to our family tree

Scientists have discovered fossils of jawbones and teeth from what may be a new species on the human family tree. This distant human relative is long extinct. It lived between 3.3 million and 3.5 million years ago in what's now Ethiopia.

Scientists have named the new species Australopithecus deyiremeda. Researchers used a partial upper jaw and two lower jaws (one recovered in two pieces), to describe the species. (Deyiremeda means "close relative" in the local Afar language.)

Yohannes Haile-Selassie of the Cleveland Museum of Natural History in Ohio and his colleagues shared details of their new find May 28 in Nature.

Paleoanthropologists like Haile-Selassie study ancient humans and their ancestors, based on fossils and cultural artifacts or symbols that they left behind. The new discovery suggests two or more species of ancient hominids coexisted in East Africa, Haile-Selassie says. (Hominids include humans and our fossil ancestors.) The new fossils were found near where another species of hominid lived at the same time. That species is best known by a partial skeleton nicknamed Lucy.

Species tend to adapt and change - sometimes so much so that they morph into a new species. The emergence of new traits, as part of that adaptation, usually comes in response to changes in the environment, food supply or perhaps climate. "The $64 million question," says Haile-Selassie, "is 'What environmental and ecological factors triggered hominid species diversity between around 4 million and 3 million years ago?'"