Earliest Human Remains Unearthed On Sulawesi, Indonesia
Archaeologists searching for skeletal remains of ancient Homo sapiens on the Indonesian island of Sulawesi have achieved their goal. In Leang Bulu Bettue cave in southwestern Sulawesi, they unearthed a human jawbone that belonged to someone who lived approximately 25,000 years ago . This is the oldest fossilized human remains ever found on the island, and offers the first direct proof that modern humans occupied Sulawesi during the late Pleistocene era (before the end of the last Ice Age ).
Searching for Human Remains on Sulawesi
The team of Australian and Indonesian archaeologists responsible for the discovery were exploring a cave that had already produced evidence of Pleistocene-era occupation by modern humans. This was in the form of two engraved portable stones , which featured pictures of a type of water buffalo that was native to Sulawesi and a celestial orb (the Sun?) that was emitting rays of light.
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A plaquette discovered in the Leang Bulu Bettue cave on the island of Sulawesi. (Courtesy of Andrew Thomson / Artnet)
These carved rock reliefs were revealed to be about 20,000 years old, and marked the first-ever discovery of this type of art at a location in Asia. Other types of ancient rock art have been discovered at other caves in Sulawesi , offering still more indirect evidence of human occupation.
Finding these two pieces of ancient art in 2020 motivated archaeologists to keep searching for human remains in the cave, and just a year later they found what they had been seeking. They identified the jawbone as having belonged to a modern human, specifically to an elderly man or woman with badly worn teeth. In fact, the only teeth still attached to the jaw were the molars.
In size this find is small, but its implications are significant, the archaeologists say.
The skeletal human remains of a Pleistocene modern human (Homo sapiens)found on Sulawesi. (Brumm et al., 2021, PLoS ONE /CC-BY 4.0 )
“The first modern humans to reach Sulawesi produced some of the oldest known dated rock art , yet little is known about the origin and cultural lives of these Late Pleistocene hunter-gatherers,” the archaeologists wrote in an article in PLoS ONE describing their discovery. They explained that the jawbone “provides us with the first direct fossil insight into the identity of these ancient foragers, and its unusual tooth wear and oral pathology offer tantalizing hints on how they adapted to their rainforest environment.”
While this is the first Pleistocene-era human fossil found on Sulawesi, it is the second such fossil discovered in the area. The first was found on the island of Alor , a small outer island of Indonesia that is located approximately 500 miles (800 kilometers) to the south of Sulawesi.
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Map of Wallacea showing the location of Sulawesi and Leang Bulu Bettue, where the fossilized human remains have been found. (Brumm et al., 2021, PLoS ONE /CC-BY 4.0 )
Why Are Ancient Human Bones So Rare On Sulawesi?
Sulawesi is part of a geographical zone in the Pacific known as Wallacea. It is one of several islands in this zone, and its location places it at the midpoint between the Malay Peninsula (mainland southeast Asia) and Australia.
The significance of this isn’t apparent looking at a map today. But when sea levels were much lower before the end of the last Ice Age (around 9,000 to 10,000 BC), most of the islands that now lie between southeast Asia and Australia were not islands at all. Instead, they were part of much larger continental landmasses called supercontinents, which connected Australia and New Guinea in the South Pacific and the islands of Malaysia and Borneo with mainland southeast Asia farther to the north.
But the islands of Wallacea remained apart from the supercontinents, even when sea levels were at their lowest. They occupied a relatively narrow slice of ocean that separated the two supercontinents, and that would have made them important stopping points for Eurasian seaborne travelers sailing from Sundaland (the southeast Asian supercontinent) to Sahul (Australia and New Guinea).
Archaeological evidence reveals that modern humans began migrating from Eurasia to what is now Australia in significant numbers approximately 65,000 to 50,000 years ago. These migrants were the ancestors of modern-day Aboriginal Australians and Papuans and also the original human settlers in the Wallacean islands.
Just how many of these ancient migrants chose to make Sulawesi and other nearby islands their home, instead of moving on to Australia and New Guinea? This is a difficult question to answer, since only two discoveries of human fossils have been reported on the islands of Wallacea so far.
This scarcity of ancient bones could mean that permanent settlers on the islands were small in number. The vast majority of the migrants may have preferred to live on the supercontinent of Sahul, where land space was far more plentiful and where people could move inland to protect themselves from the ravages of tropical storms. Any settlements that were built on Sulawesi may have existed exclusively to serve the needs of migrants who’d come from the Eurasian mainland and needed to stop on the island to rest and resupply before moving on to their final destination.
It's also possible that Pleistocene-era human populations on Sulawesi and on the rest of the Wallacean islands were higher than the fossil record seems to indicate. Climate and soil conditions in tropical regions can cause skeletal remains to decay relatively rapidly, and that may explain why archaeologists searching for human bones on Sulawesi have mostly come up empty.
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Stalagmite 437 in situ within the trench under excavation–during the excavation the stalagmite was left in situ on a plinth of unexcavated Layer 4a sediments, with (bottom right) human maxilla (jawbone) fragments (Maros-LBB-1a) in situ in Layer 4a below the base of Stalagmite 437. (Brumm et al., 2021, PLoS ONE /CC-BY 4.0 )
Did Humans Meet Denisovans in Wallacea?
There is a possibility that ancient human populations living on the islands of Wallacea may have interacted with the legendary Denisovans. These archaic cousins of modern humans went extinct sometime during the last Pleistocene era, and what little is known about them comes primarily from archaeological discoveries made in Siberia. But traces of their DNA have been detected in the genomes of the indigenous people of Australia and New Guinea, and in DNA samples taken from post-Ice-Age human fossils found on Sulawesi as well.
If they encountered each other on the islands of Wallacea, modern humans and Denisovans may have interbred during the late Pleistocene era. This would explain why Denisovan DNA found a foothold in the region, one that lasts to this very day.
There is still much scientists don’t know about the migratory patterns and lifestyle choices of the humans who left Eurasia more than 50,000 years ago and moved across the Pacific Ocean to inhabit new land areas to the south and east. Fossilized skeletal remains can help answer some of the questions, however, which is why the discovery of the 25,000-year-old human jawbone on Sulawesi is so significant. If someday Denisovan fossils are found there as well, that could be even more revelatory.
Top image: An overview of the trench in the rock-shelter area at Leang Bulu Bettue, Sulawesi, from where the human remains have been excavated. Source: Brumm et al., 2021, PLoS ONE /CC-BY 4.0
By Nathan Falde