Archaeologist finds first fossil evidence of chimps in Kenya

The discovery of the first fossil chimpanzee in Kenya’s Rift Valley is reported in a paper co-authored by UConn professor of anthropology Sally McBrearty in the Sept. 1 issue of the international science journal Nature.

McBrearty found four fossil chimpanzee teeth during her archaeological research in summer 2004 in the Rift Valley of Kenya. She says she and anthropologist Nina Jablonski of the California Academy of Sciences, co-author of the paper, were very surprised with the find: no one had ever found a chimpanzee fossil before.

“We were going through the fossils near the end of the season and I realized they were something interesting,” says McBrearty.

After analyzing them at the National Museums of Kenya and consulting with paleontologist Meave Leakey, they identified the teeth as those of a chimpanzee of the genus Pan. It lived about 500,000 years ago and died at the age of about seven or eight.

Most scientists are looking for human fossils, McBrearty says, and it was assumed that humans – but not chimps – lived in the Rift Valley. The valley, a dry environment, was thought to have been a barrier to chimpanzees, who stayed in the rain forest where they live today.

It was even proposed that this type of barrier might have caused the separation of the chimp and human lines 7 million years ago, McBrearty says: humans adapted to the savannah and began to walk on two legs, while chimpanzees, the closest living relative of humans, stayed in the rain forest and remained quadrupeds.

Finding the chimp fossils in an area where humans lived at the same time means “that scenario is out,” she says.

“As an archaeologist, it’s interesting to imagine how they might have interacted with each other,” she adds.

The find shows that both chimps and humans were able to adapt to a drier environment, and that chimps had a range that included East Africa, some 600 kilometers east of where they live today, she noted.