Above, one of the most famed of the ancient apes, Proconsul africanus (Dryopithecus).

A 10 million-year-old jawbone and teeth discovered in Kenya may represent a new species very close to the last common ancestor of gorillas, chimpanzees and humans, according to a study published in the U.S. Proceedings of the National Academy of Sciences on November 12, 2007.

Researchers from the Primate Research Institute of the Kyoto University in Japan found the jawbone, along with 11 teeth in volcanic mud flow deposits in the Nakali region of Kenya, in 2005. The last time a hominoid fossil of this period was found in Kenya was 1982.

Fossils from this era are so rare that some researchers have proposed that the last common ancestor might have left Africa for Europe and Asia and then returned later. But the findings of the Japanese archaeologists indicate that the ancestor of African great apes and humans likely evolved entirely in Africa.

The new species, Nakalipithecus nakayamai, resembles the candidate formerly thought the closest to a common ancestor, Ouranopithecus macedoniensis, from Greece. However, several details of the dentition, which indicate a less specialized diet than Ouranopithecus, place Nakalipithecus in a genus of its own.

In addition to the new Kenyan species of ancient ape (Nakalipithecus nakayamai), evidence recently emerged of another ancient African ape. In August, a team of Japanese and Ethiopian paleontologists announced that they had uncovered 10-million year-old teeth fossils in Ethiopia’s Afar region in 2006 and 2007. The scientists said the teeth probably belonged to a “proto-gorilla” species which they named Chororapithecus abyssinicus.