August 9, 2007

Fossil Finds Challenge View of Man’s Place in Evolution

By Steve Bloomfield

Two fossils discovered in northern Kenya directly challenge the established view that there was a linear progression from apes to humans.

Scientists have long believed that humans today, Homo sapiens, descended from Homo erectus, which in turn evolved from Homo habilis. But new research, led by the world-renowned palaeontologist Meave Leakey, suggests that Homo habilis and Homo erectus lived side by side in eastern Africa for more than 500,000 years.

Dr Leakey's team discovered two fossils in Turkana, northern Kenya, in 2000, but it took seven years of research and laboratory work by the Koobi Fora Research Project in Kenya to uncover their importance.

One of the fossils, an upper jaw bone of Homo ha-bilis, is 1.44 million years old, making it far more recent than all previous discoveries of Homo habilis bones. It had previously been thought that only Homo erectus existed at this time. "Their coexistence makes it unlikely that Homo erectus evolved from Homo habilis," said Dr Leakey. "The fact that they stayed separate as individual species for a long time suggests that they had their own ecological niche, thus avoiding direct competition." Homo habilis was likely to be vegetarian, while Homo erectus ate meat.

Fred Spoor, professor of evolutionary anatomy at University College London, who co-authored the report on the findings in this week's issue of Nature, said the fossils would challenge common conceptions of evolution. "Human evolution appears to be less linear than we thought," he said, speaking from the eastern shores of Lake Turkana, where he and Dr Leakey are conducting fresh research. "As the pattern of evolution becomes more clear it seems we are not so unique. We are more like other mammals - it places us more in the animal kingdom."

The second discovery, of a skull of Homo erectus, was dated to 1.55 million years ago. It is the smallest Homo erectus skull ever found, leading researchers to believe that Homo erectus may have been very similar to modern gorillas and not as human-like as once thought.

"In gorillas males are much larger than females, and this sexual dimorphism is related to their strategy of having multiple mates," said Susan Anton, associate professor of anthropology at New York University. "The new Kenyan fossil suggests that, contrary to common belief, this may have been true of Homo erec-tus as well."

Frederick Manthi, a senior scientist at the National Museums of Kenya who first spotted the Homo erec-tus skull, said the findings further emphasised the importance of the region in uncovering more about human ancestry. "With more research we should be able to find more fossils to discover more about our ancestry." But he warned that without funding from overseas little research could be carried out.

The newest finds are the latest in a series of discoveries by three generations of Leakeys that have challenged established views on how humans evolved. Louis Leakey was one of the 20th century's greatest anthropologists, while his wife, Mary, was responsible for some of the most remarkable finds, including the discovery of 3.6- million-year-old hominid footprints preserved in volcanic ash in Tanzania in 1978. Their son, Richard, became director of the Kenya Wildlife Service. His wife, Meave, and daughter, Louise, head the Koobi Fora Research Project, part of the National Museums of Kenya.

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