Anthropologist finds first chimp fossil

Anthropology Professor Sally McBrearty and anthropologist Nina G. Jablonski of the California Academy of Sciences have just published in the international science journal Nature their discovery of the first fossil chimpanzee.

McBrearty found four fossil chimpanzee teeth during her archaeological research in the summer of 2004 in the Rift Valley of Kenya. Jablonski and McBrearty 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," said McBrearty.

After analyzing them at the National Museums of Kenya in Nairobi and consulting with paleontologist Meave Leakey, famous for her discoveries of some of the earliest human fossils, they identified the teeth as those of a chimpanzee, of the genus Pan , who lived about 500,000 years ago and died at the age of about seven or eight.

Most scientists are looking for human fossils, McBrearty said, and it was assumed that humans, but not chimps, lived in the Rift Valley. It was thought that the Rift Valley, a dry environment, was a barrier to chimpanzees, who were thought to stay in the rain forest, where they live today.

It was even proposed that this type of barrier may have caused the separation of the chimp and human lines 7 million years ago, McBrearty said - humans adapted to the savannah and began to walk on two legs, while chimpanzees, the closest living relative to 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," said McBrearty.

 "As an archaeologist, it's kind of interesting to imagine how they might have interacted with each other," she said.

The find shows that both chimps and humans were quite 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. It also suggests that the Rift was more densely wooded 500,000 years ago and that more animals lived there, before people cut down the trees.

Fossils of Homo erectus or Homo rhodesiensis , were found in the 1960s and 1980s in this same area, dating to the same time period. These human species immediately preceded our own, Homo sapiens , which appeared about 300,000 years ago.

The chimp fossils were found in an open area that had been exposed by erosion. Half a million years ago, it would have been close to the shore of Lake Baringo, which is now several kilometers to the west.

McBrearty, who came to UConn 10 years ago from Brandeis University, has worked in East Africa for 30 years. Her work is concentrated in the Kapthurin Formation, a large area with about 60 fossil sites near Lake Baringo in Kenya. She is affiliated with the National Museums of Kenya.

Her research has been funded almost continuously since 1993 by the National Science Foundation.