Washington: A new study suggests that no known hominin is ancestor to the Neanderthals or modern humans.
The researchers, using quantitative methods focused on the shape of dental fossils, find that none of the usual suspects fits the expected profile of an ancestor of Neanderthals and modern humans.
They also present evidence that the lines that led to Neanderthals and modern humans diverged nearly 1 million years ago, much earlier than studies based on molecular evidence have suggested.
The study was carried out by an international team of scholars from The George Washington University, Konrad Lorenz Institute for Evolution and Cognition Research in Austria, Indiana University and Atapuerca Research Team in Spain.
"Our results call attention to the strong discrepancies between molecular and paleontological estimates of the divergence time between Neanderthals and modern humans," Aida Gomez-Robles, lead author of the paper and a postdoctoral scientist at the Center for the Advanced Study of Hominid Paleobiology of The George Washington University, said.
"These discrepancies cannot be simply ignored, but they have to be somehow reconciled," the author said.
The researchers use techniques of morphometric analysis and phylogenetic statistics to reconstruct the dental morphology of the last common ancestor of Neanderthals and modern humans. They conclude with high statistical confidence that none of the hominins usually proposed as a common ancestor, such as Homo heidelbergensis, H. erectus and H. antecessor, is a satisfactory match.
"None of the species that have been previously suggested as the last common ancestor of Neanderthals and modern humans has a dental morphology that is fully compatible with the expected morphology of this ancestor," Gomez-Robles said.
The study also finds that the potential human ancestors discovered in Europe are morphologically closer to Neanderthals than to modern humans.
This suggests the line leading to Neanderthals arose around 1 million years ago and the divergence of humans took place much earlier than previously thought. Other studies have placed the divergence around 350,000 years ago.
The research is set to be published online by the Proceedings of the National Academy of Sciences.
