Last updated April 23, 2018 at 11:39 am
Delving deeper into a Sulawesi site shows Ice Age hunter-gatherers long preceding cave art culture of later groups.
Leang Burung 2, is located on the Indonesian island of Sulawesi, one of the key stepping stones as humans spread out. Credit: David McGahan
Humans may have occupied an Indonesian rock shelter 15,000 years earlier than previously thought, archaeologists say, providing new insights into the history of human migration and cultural evolution.
The limestone rock shelter, called Leang Burung 2, is located on the Indonesian island of Sulawesi, which is part of the vast Wallacea archipelago sandwiched between today’s Borneo and Papua New Guinea.
These oceanic islands are assumed to be key stepping stones for early modern humans as they spread downwards from continental Asia and into Australia, as early as 65,000 years ago.
Leang Burung 2 was first excavated in 1975, uncovering artifacts that suggested the site had been occupied as early as between 24,000 and 35,000 years ago.
Simple stone tools
However, excavations stopped before reaching the sedimentary layers with no evidence of humans, meaning archaeologists couldn’t be certain that this occupation had been the first.
Now, new research delves deeper — literally. Led by Adam Brumm from Griffith University’s Australian Research Centre for Human Evolution, an international team of archaeologists revisited the site in 2007 and between 2011–13 to dig three metres deeper than before.
The team uncovered artifacts that show that humans were living at the site 15,000 years earlier than previously thought.
“We found simple stone tools clearly made by humans using large river cobbles as the main source of raw material, along with numerous animal fossils, at least some of which probably reflect the discarded food remains left by people inside the shelter,” says Brumm.
“We think that humans lived at Leang Burung 2 at least 50,000 years ago.”
The team suggest that in earlier excavations, the upper layers of sediment had been disturbed and mixed up, affecting the accuracy of dating.
Mystery remains
This finding is not the first to bring Sulawesi to the world’s attention. Back in 2014, Australian researchers showed that cave art in the region of Maros, in southern Sulawesi, dates back to at least 40,000 years ago, comparable to the world’s oldest cave paintings at El Castillo in northern Spain.
Furthermore, excavations at a site just 80 kilometres away from Leang Burung 2 unearthed stone tools dating back to between 118,000 and 194,000 years ago. Exactly who made these tools remains a mystery.
“The island of Sulawesi is located near the edge of the Asian continent, with its ancient population of Homo erectus, and north of Flores, home to the famous ‘Hobbit’ (Homo floresiensis),” says Brumm.
“It is also thought that the so-named ‘Denisovan’ hominins, close relatives of the Neanderthals, were present somewhere in Wallacea and that they interbred with early ancestors of present-day Aboriginal Australian and Melanesian peoples.”
The incredible age of the tools may suggest that Sulawesi’s first inhabitants were groups of archaic humans, long preceding cave art culture of later groups.
Similarly, the researchers aren’t sure who was the first to occupy Leang Burung 2. The first inhabitants could have been the same early modern humans who later went on to produce the 40,000-year-old paintings in nearby caves, or they could have been a now-extinct group that was later replaced by our species.
Human migration
“Whoever the early inhabitants were, our research suggests they lived alongside (and possibly hunted) the island’s largest animals, including now-extinct elephants, and employed a tool technology very similar to that used 200,000 years ago on Sulawesi,” Brumm says.
If the inhabitants were archaic humans, Brumm notes that “it is even possible these people were still around when Homo sapiens were creating rock art at nearby caves 40,000 years ago.”
Studying human migration through Sulawesi is key to understanding when and how Aboriginal people first arrived in Australia, because the path they took from continental Asia to northern Australia remains uncertain.
“Sulawesi is in the middle of one of two most likely island-hopping routes to Australia,” Brumm explains. “This island might have been the launching pad for the human voyage to Australia. It could even have been where ancestral Aboriginal people came face to face with Denisovans.”
Intriguingly, the most recent round of excavations still haven’t reached deep enough to hit the lowest layers of the site, where there is no human presence. Exploring the site further may therefore reveal even older artifacts, pushing back the site’s occupation past 50,000 years.
Research at Leang Burung 2 has also led the team to another cave in the area with much better potential: Leang Bulu Bettue. Excavations here have unearthed rare jewellery and other art that are potentially up to 30,000 years old.
“If we are lucky, we might uncover the first fossils of early humans, throwing new light not only on the prehistory of Sulawesi but the fascinating saga of human evolution in the wider region,” Brumm concludes.
The research is published in PLOS ONE.
