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In the study, researchers from the George Washington University, Konrad Lorenz Institute for Evolution and Cognition Research in Austria, Indiana University and the Atapuerca Research Team in Spain examined about 1,200 fossilized molars and premolars from 13 species or types of humans and human relatives and ancestors.
Using a quantitative method, they reconstructed the expected dental morphology of the last common ancestor of Neanderthals and modern humans to assess whether the species were compatible with this ancestral position. They found that species such as the Homo heidelbergensis, H. erectus and H. antecessor did not match the profile.
In addition, the researchers found new evidence that the lines that led to Neanderthals and modern humans diverged nearly 1 million years ago, that is, much earlier than indicated by prior studies based on molecular evidence, which suggested that divergence took place around 350,000 years ago.
"None of the species that have been previously suggested as the last common ancestors of Neanderthals and modern humans have a dental morphology that is fully compatible with the expected morphology of this ancestor," concluded Dr. Aida Gómez-Robles, lead author and a postdoctoral student at the George Washington University. "Our results call attention to the strong discrepancies between molecular and paleontological estimates of the divergence time between Neanderthals and modern humans," she said.
The study, titled "No Known Hominin Species Matches the Expected Dental Morphology of the Last Common Ancestor of Neanderthals and Modern Humans," was published online on Oct. 21 in the Proceedings of the National Academy of Sciences.
