Fossilized bones and stone artifacts discovered in a limestone cave on the Indonesian island of Flores suggest that Homo floresiensis – an extinct human ancestor nicknamed the Hobbit – may have died off tens of thousands of years earlier than we thought. The findings are published in Nature this week.
Excavations at Liang Bua from 2001 to 2004 uncovered skeletal remains of the chimpanzee-sized Homo floresiensis at depths of 4 to 7 meters (12 to 23 feet) in multiple places. The Hobbit-bearing deposits, associated stone artifacts, and the remains of extinct animals (including molars of the elephant-like Stegodon) were dated to between 95,000 and 12,000 years – which is surprisingly recent.
From 2007 to 2014, a large international team led by University of Wollongong’s Thomas Sutikna and Richard Roberts and Lakehead University’s Matthew Tocheri conducted new excavations at Liang Bua. When they exposed previously unexplored parts of the cave, they found that the sediment layers weren’t deposited evenly.
"As we extended our original excavations each year, it became increasingly clear that there was a large remnant pedestal of older deposits truncated by an erosional surface that sloped steeply toward the cave mouth," Sutikna said in a statement. The previous discoveries may have been given a younger age than they actually were.
The team sieved through several sectors with dimensions of 2 x 2 meters (6.6 x 6.6 feet) and 1 x 2 meters (3.3 x 6.6 feet), some reaching depths of more than 8 meters (26 feet). Then, using the uranium-series technique, the team dated three Homo floresiensis ulnas and seven Stegodon bones. They also dated stalagmites, feldspar and quartz grains, and crystal and charcoal samples from the cave using multiple methods ranging from radiocarbon to argon-argon.
The skeletal remains and the deposits containing them date back about 100,000 to 60,000 years, and the associated stone artifacts range from about 190,000 to 50,000 years old. That means hobbits were using the cave up until 50,000 years ago – and not as recently as 12,000 years ago.
We know that modern humans reached Australia (via Indonesia) by about 50,000 years ago, but we don’t know if Homo floresiensis survived long enough to meet up with Homo sapiens on Flores or with Denisovans dispersing through Southeast Asia.
"Currently, the earliest evidence of modern humans on Flores is 11,000 years ago. But the fact that the Hobbits disappear about 50,000 years ago is coincident with when modern humans reached Australia, and they didn’t get there by flying over the islands in between," Tocheri explained to IFLScience. "It implies that modern humans might have had something to do with the disappearances, but we need to find direct evidence of that to know for sure."
The Liang Bua Team prepares for new excavations. Smithsonian Digitization Program Office/Liang Bua Team
Image in the text: Liang Bua Team