Ancient teeth make Homo sapiens the lead suspect in the extinction of Homo floresiensis.
A pair of 46,000-year-old human teeth has been discovered in Liang Bua, a cave on the Indonesian island of Flores that was once home to the 1-metre-tall ‘hobbit’ species Homo floresiensis. The teeth are slightly younger than the known hobbit remains, which strengthens the case that humans were responsible for the species’ demise.
A team led by archaeologist Thomas Sutikna and geochronologist Richard Roberts, both at the University of Wollongong, Australia, reported the discovery of the teeth in a talk on 17 September at the annual meeting of the European Society for the study of Human Evolution in Madrid.
The 2003 discovery of H. floresiensis puzzled researchers, in part because some of the remains were carbon dated to 11,000 years ago1,2,3. By then, Homo sapiens had colonized southeast Asia, and few scientists could imagine them having co-existed with hobbits for thousands of years.
But this year, re-dating work in the cave pushed the extinction of hobbits back to around 50,000 years ago4. Roberts, who led that study, noted that humans were known to be already living in southeast Asia around that time. “It’s a smoking gun for modern human interaction, but we haven’t yet found the bullet,” he told Nature when the paper was published in March 2016.
The human upper premolar and lower molar teeth were discovered in 2010 and 2011 and carbon dated to around 46,000 years old using nearby charcoal, Sutikna told attendees at the meeting. The team is confident that the teeth are from H. sapiens: they are larger than those of H. floresiensis, for instance.
María Martinón-Torres, a palaeoanthropologist at University College London who attended the talk, thinks that the lower molar looks like those of H. sapiens, whereas the premolar seems a bit more primitive. To prove conclusively that the teeth are human, she would like to see comparisons with a wide range of remains from H. sapiens and also from H. erectus (which might have survived in Indonesia until around 50,000 years ago). “I think they have quite a tough job. There are lot of factors to take into account,” she says.
Other evidence presented by Sutikna puts humans in Liang Bua very soon after H. floresiensis vanished, which adds weight to the possibility that humans played a role in the extinction of hobbits, possibly by out-competing them for limited resources on Flores. Evidence of animals that might have been prey for human hunter–gatherers, such as giant storks (Leptoptilos robustus), vultures (Trigonoceps) and miniature elephants called stegodons (Stegodon florensis insularis), vanishes from the cave’s sediment layers after around 46,000 years ago. At the same time, freshwater mollusc shells begin to appear in sediments. Such shellfish are common at early human sites across Eurasia and Africa. Stone tools made from chert (which are also regularly found at other human sites) and evidence for fire hearths are also more recent than the hobbit remains at Liang Bua5.
“What we don't yet know is whether there was at least a short overlap in the populations, thus raising the question once again of the possible role of modern humans in the extinction of floresiensis,” says Chris Stringer, a palaeoanthropologist at the Natural History Museum in London who attended the meeting. If hobbits and humans overlapped, they might even have interbred, Stringer says.
Next April, Sutikna, Roberts and their team will return to Liang Bua to explore cave deposits that are between 46,000 and 50,000 years old: they may hold the remains of humans who saw the very last hobbits.
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Callaway, E. Human remains found in hobbit cave. Nature (2016). https://doi.org/10.1038/nature.2016.20656