NEW YORK -- Scientists say a fragment of jawbone found in Ethiopia is the oldest known fossil from an evolutionary tree branch that eventually led to modern humans.

The fossil comes from very close to the time that the human branch split away from more ape-like ancestors that are best known for the fossil skeleton Lucy. So it gives a rare glimpse of what very early members of the modern human branch looked like. Our branch is called Homo.

The fossil is about 2.8 million years old. Its discovery was reported Wednesday in the journal Science.