7-million-year-old fossils widen divide between humans and chimps

A new study on human evolution sparks struggle of Darwinian proportions. Cheryl Jones reports.

This is a 7.24 million year old upper premolar of a Graecopithecus from Azmaka, Bulgaria.
Wolfgang Gerber, University of Tübingen

A row has erupted over claims the human and chimpanzee lineages might have split hundreds of thousands of years earlier than previously thought.

Research based on a study of the ancient skeletal remains of the species Graecopithecus freybergi, from the eastern Mediterranean, is published in two papers in the journal PLoS One.

A big international team of researchers co-led by Madelaine Boehme, of the University of Tubingen, Germany, says that G. freybergi might be the common ancestor of members of the genus Homo and of chimps.

The research team contends the split might have occurred in the eastern Mediterranean.

The study of prehistory is confounded by a sparse fossil record that has nevertheless generated a dizzying number of possible family trees. It is exacerbated by problems in the dating of material from archaeological sites that have been disturbed.

The team did CT scans of a lower jawbone from Greece and an upper premolar tooth from Bulgaria dated to between 7.18 million and 7.27 million years old. But it drew anatomical data on other species, including gorillas, and chimps, from the scientific literature or casts of the remains.

Debbie Argue, an evolutionary biologist at the Australian National University, in Canberra, says more fossil evidence is needed to confirm the taxonomic status of G. freybergi.

Argue’s colleague Colin Groves says more comparisons should have been made with the genus Ouranopithecus, also from Europe, as candidates for the common ancestor.

“In the past, the two genera have been thought of as the same,” he says.

But Boehme says the database of fossil material “is not so bad”. “The conclusion may sound extravagant to some experts, but these two papers are just the beginning,” she says. “The forthcoming years will see a revolution in our ideas of human evolution.”

Cheryl Jones is a science writer and co-author of “The Bone Readers: atoms, genes and the politics of Australia’s deep past”, published by Allen & Unwin.
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