Until recently, there were no known fossil remains of chimpanzees. Then in 2005, anthropologists Sally McBrearty and Nina Jablonski published a paper in the journal Nature describing three fossil chimpanzee teeth that had been unearthed from the Kapthurin Formation, a basalt outcrop west of Lake Baringo in Kenya. This discovery offered new insight into the lives ancestral chimpanzees.
Today, chimpanzees inhabit the tropical forests of West and Central Africa and are absent from the dryer habitats in East Africa. Scientists have long speculated that when chimpanzees and ancestral humans diverged between 5 and 8 million years ago, each went their separate way. Chimpanzees favored the wetter climes and tropical forests common to West and Central Africa. Human ancestors preferred the dryer savanna habitats of the East African Rift Valley, a lowland trench that stretches from Ethopia to Mozambique. But the fossil chimpanzee teeth found in the Kapthurin Formation contradict this view. Instead, these fossils indicate that ancient chimpanzees lived within the East African Rift Valley and that a clear-cut "splitting" of chimpanzee and human ranges did not occur.
Sally McBrearty and Nina Jablonski analyzed the fossil chimpanzee teeth and determined them to be about 545,000 years old, an age that places them within the Middle Pleistocene. Other fossils from that time period found nearby indicate that the ancient chimpanzees shared their habitat with crocodiles, hippopotamuses, carnivores, elephants, turtles, gastropods, tiny mammals, and Homo species such as Homo erectus and Homo rhodesiensis.
Analysis of the sediments gave clues to what the habitat of the area was like during the Middle Pleistocene. It appears that the region was probably wooded and was on the shores of a lake that alternated between freshwater and salt-alkaline water conditions.
Refs:
McBrearty, S., & Jablonski, N. (2005). First fossil chimpanzee Nature, 437 (7055), 105-108 DOI: 10.1038/nature04008
Photo © Anup Shah / Getty Images.
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