Scientists in northeastern Ethiopia have discovered the skull of a small human ancestor that could be a missing link between the extinct Homo erectus and modern humans.

The hominid cranium was found in two pieces last month near the town of Gawis in the Afar region of northeastern Ethiopia. It is believed to be between 250,000 and 500,000 years old, a very significant period in the history of humanity.

The face and cranium of the fossil are recognizably different from that of modern humans but it bears unmistakable anatomical evidence that it was an ancient human.

"The Gawis cranium provides us with the opportunity to look at the face of one of our ancestors," Sileshi Semaw, director of the Gona Paleoanthropological Research Project in Ethiopia, said in a statement. "This fossil links us with the past by showing a face that is recognizably different and more primitive than ours."

Sileshi, an Ethiopian paleoanthropologist based at Indiana University, said most fossil hominids are found in pieces, but a near-complete skull, a rare find, provides a wealth of information.

Homo erectus, which many believe was an ancestor of modern Homo sapiens, is thought to have died out 100,000 to 200,000 years ago.

The cranium dates to a time about which little is known, the transition from African Homo erectus to modern humans. The fossil record from Africa for this period is sparse and most of the specimens poorly dated, project archeologists said.