Researchers studying human origins have long argued that some of the earliest primates lived in Eurasia. As the story goes, some of them eventually made their way into Africa where, between six and eight million years ago, the group split in two: one lineage headed toward modern-day apes and the other eventually became humans.
But when, where and why they split is still intensely debated. Now, two new controversial studies published in the journal PLOS One are stoking the fire, suggesting that the last common ancestor of great apes and humans actually lived in Southern Europe, not in Africa.
As Ben Guarino at The Washington Post reports, to come to their conclusion, the international team of researchers analyzed fossils from a species called Graecopithecus freybergi, or “El Graeco,” only known from two specimens. In 1944, German soldiers dug up the first of these specimens while building a bunker outside Athens, Greece. The second is a single upper premolar tooth found in Bulgaria.
According to a press release, the team used computer tomography to examine the jawbone and tooth in detail, and visualize the internal structures in the jaw. What they found is that the roots of the premolar teeth of El Graeco are fused, a trait they say is found only in the pre-human lineage and not in apes.
“While great apes typically have two or three separate and diverging roots, the roots of Graecopithecus converge and are partially fused—a feature that is characteristic of modern humans, early humans and several pre-humans including Ardipithecus and Australopithecus,” says study leader Madelaine Böhme from the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen in Germany, in the release.
The researchers also dated the fossils to between 7.24 and 7.125 years old, making them the oldest pre-human fossils ever found—even older than Sahelanthropus tchadensis, a six- to seven-million-year-old primate believed to among the earliest humanlike species. Taken together, the results suggest that the split between great ape and human lineages happened in Southern Europe, not Africa.
Not everyone is convinced by the research. “I really appreciate having a detailed analysis of the Graecopithecus jaw—the only fossil of its genus so far,” Rick Potts, head of the Smithsonian’s Human Origins Program tells Guarino. “But I think the principal claim of the main paper goes well beyond the evidence in hand.”
Jay Kelley, a paleontologist at Arizona State University's Institute of Human Origins also tells Guarino that the tooth evidence is not as significant as it seems. He says some of the earliest-known hominins didn’t have fused teeth roots and some later human ancestors did, meaning it’s not strong evidence that El Graeco is an early pre-human.
Potts agrees. In an email to Smithsonian.com, he says he’s not convinced by the tooth evidence, especially since so few samples were studied. Instead of being an early pre-human, he says it’s likely El Graeco is related to European apes. “Analyses by other research groups…suggest that Graecopithecus—known only from the single mandible with hardly any tooth crowns preserved—is closely related to the much better documented Ouranopithecus, also a late Miocene ape found in Greece,” Potts writes.
Potts also says that the location doesn’t add up as the place where apes and pre-humans split. “A hominin or even a hominine (modern African ape) ancestor located in a fairly isolated place in southern Europe doesn’t make much sense geographically as the ancestor of modern African apes, or particular the oldest ancestor of African hominins,” he writes.
But the researchers of these latest studies seem convinced that El Graeco is a pre-human. As Jen Viegas at Seeker reports, the researchers say it is possible that the descendants of Graecopithecus could have wandered into East Africa, the hotbed of hominin evolution. They argue that a changing climate in southern Europe and a developing savannah ecosystem—giraffes, rhinos, gazelles and more—could have pushed the split between apes and humans.
Though the conclusions will likely be debated for years to come. The researchers have come up with a catchy name for the idea: They are calling their hypothesis the “North Side Story.”