Several sets of teeth suggest that ancient humans roamed Europe thousands of years earlier than previously thought.
A jawbone and its teeth discovered in a South England cave, Kent’s Cavern, in 1927 is more than 41,000 years old, suggests new dates linked to animal remains in the same cave. Meanwhile, two teeth excavated from a southern Italian site, Grotta del Cavallo, in the 1960s and attributed to Neanderthals may instead belong to modern humans. At 43,000 to 45,000 years old, they are the oldest anatomically modern human remains identified in Europe.
Together the two new studies (which are published online today in Nature) emphasize how much archaeologists have to learn about early human forays into Europe. Instead of making a single trek from Africa and the Middle East into Eastern Europe and then striking north and west, the first humans to reach Europe may have expanded in bursts, says Chris Stringer, a paleoanthropologist at the Natural History Museum in London who was involved in the Kent’s Cavern paper. Brief warm spells would have pushed the hunter-gatherers into new territory. “They followed their food,” he suggested at a press briefing this morning.
The archaeologists who discovered the Kent’s Cavern jaw originally classified it as modern human, based on the stone tools found around it. In the late 1980s scientists used carbon dating (which measures the gradual decay of radioactive carbon-14 relative to non-radioactive carbon) to come up with an age of about 35,000 years old.
However, carbon dating of bones older than about 30,000 years is skirting the limits of the technology, because by that age nearly all of the radioactive carbon has decayed, says Tom Higham, a researcher at the University of Oxford, UK who led the new Kent’s Cavern study. This means that even slightest contamination from younger remains at a site or animal glues used to assemble a fossil could provide dates thousands of years too young.
To get around this problem, Higham’s team extracted and purified collagen in bones from animals such as woolly rhinoceroses that were excavated above and below the jawbone. They tried to purify collagen from a tooth attached to the jaw, but couldn’t obtain enough to date it. But the animal remains bookended the human bones to between 44,000 and 41,000 years old, making them the oldest human remains in north-western Europe. They are nearly contemporary with 42,000-year-old bones from a Romanian site, which are the oldest human remains in Europe based on the direct dating of human bones.
The two molars from Grotta del Cavallo could supplant the Romanian remains as the oldest human remains in Europe. Scientists described the teeth in 1967 as Neanderthal and assumed that the stone tools and shell bead ornaments excavated around them were also made by the archaic humans. These and artefacts like them – known as Uluzzian technology – are found elsewhere in Italy and have been touted as evidence that Neanderthals, like humans, were capable of complex behaviour and symbolic thought.
However, a re-examination by Stefano Benazzi, of the University of Vienna in Austria, and his team now suggest the two teeth are human. The researchers compared numerous morphological measurements of the molars made using a computerized tomography scanner to other human and Neanderthal, and conclude they are a closer match to modern humans. His team also conclude that humans, not Neanderthals, made the Uluzzian technologies.
João Zilhão, a paleoanthropologist at the University of Barcelona, Spain, who has published numerous studies that advocate for complex behaviour among Neanderthals calls Benazzi’s paper a house of cards. Zilhão says Benazzi’s team compared the molars to too few modern humans and Neanderthals to draw a firm conclusion. He also points to a Neanderthal site in Spain, Cueva de los Aviones, which contains ornamental shells.
After the press briefing, Higham told me about a project he is working on to re-date numerous human and Neanderthal sites in Europe around this time period. Several themes appear to be emerging. Humans arrive and Neanderthals disappear from Europe in a mosaic pattern, overlapping for perhaps thousands of years in some places and not at all in others.
Geneticists have found no evidence that Neanderthals interbred with humans in Europe, and fossils described by some paleoanthropologists as hybrids between the two are controversial. Knowing when and where humans and Neanderthals may have overlapped in Europe should guide both camps looking for solid proof that they interbred.
Image of the Kent’s Cavern jawbone courtesy Chris Collins (Natural History Museum, London) and Torquay Museum.