(CNN) – The bones of a teenage hunter-gatherer who died more than 7,000 years ago on the Indonesian island of Sulawesi tell the story of a hitherto unknown human group.
According to new research, this distinct human lineage has never been found anywhere else in the world.
The study was published this Wednesday in the Nature magazine.
“We have discovered the first ancient human DNA in the island region between Asia and Australia, known as ‘Wallacea’, providing a new insight into the genetic diversity and population history of early modern humans in this little-known part of the world.” said study co-author Adam Brumm, a professor of archeology at Griffith University’s Research Center for Human Evolution, via email.
Early modern humans used the Wallacea Islands, primarily the Indonesian ones that include Sulawesi, Lombok and Flores, when they crossed from Eurasia to the Australian mainland more than 50,000 years ago, the researchers believe. However, the exact route or how they navigated during this journey is unknown.
“They must have done it using some kind of relatively sophisticated boat, since there were no land bridges between the islands, not even during the glacial peaks of the last ice age, when global sea levels were up to 140 meters lower than today.” Brumm explains.
Tools and cave paintings have suggested that humans lived on these islands 47,000 years ago, but the fossil record is scarce and ancient DNA degrades more rapidly in the tropical climate.
However, researchers discovered the skeleton of a 17 to 18-year-old woman in a Sulawesi cave in 2015. Her remains were buried in the cave 7,200 years ago. It belonged to the Toalean culture, which is only found in one area of the southwestern peninsula of Sulawesi. The cave is part of an archaeological site called Leang Panninge.
“The Toaleans is the name archaeologists have given to a rather enigmatic culture of prehistoric hunter-gatherers that lived in the forested plains and mountains of southern Sulawesi between about 8,000 years ago and about the fifth century AD,” explains Brumm. via email. “They made very distinctive stone tools (including finely crafted tiny arrowheads known as ‘Maros points’) that are nowhere else on the island or in Indonesia in general.”
The young hunter-gatherer is the first practically complete and well-preserved skeleton associated with Toalean culture, Brumm said.
The study’s lead author, Selina Carlhoff, was able to recover DNA from the wedge-shaped petrous bone at the base of the skull. “It was a great challenge, as the remains had been greatly degraded by the tropical climate,” Carlhoff, also a doctoral candidate at the Max Planck Institute for the Science of Human History in Jena, Germany, said in a statement.
The secrets that DNA hides
The work to recover the genetic information paid off.
The young woman’s DNA proved that she descended from the first wave of modern humans that reached Wallacea 50,000 years ago. This was part of the initial colonization of “Greater Australia”, that is, the combined ice age landmass of Australia and New Guinea.
These are the ancestors of today’s indigenous Australians and Papuans, Brumm said.
And it turns out that the oldest genome traced to the Wallacea Islands revealed something else: ancient humans previously unknown.
He also shares ancestry with a separate and distinct group from Asia that likely arrived after the colonization of Greater Australia, as modern indigenous Australians and Papuans do not share ancestry with this group, Brumm said.
“Previously, it was thought that the first time that people with Asian genes entered Wallacea was around 3,500 years ago, when Austronesian-speaking farmers from Neolithic Taiwan crossed the Philippines and arrived in Indonesia,” he said.
“It suggests that there may have been a different group of modern humans in this region that we had no idea about until now, as archaeological sites are very rare in Wallacea and ancient skeletal remains are rare.”
There are no descendants of this lineage left.
Its genome included another trace of an enigmatic and extinct group of humans: the Denisovans. The handful of fossils that indicate that these first humans ever existed come mostly from Siberia and Tibet.
“The fact that their genes are found in the Leang Panninge hunter-gatherers supports our earlier hypothesis that Denisovans occupied a much wider geographic area” than previously understood, the study co-author said in a statement. Johannes Krause, Professor of Archaeogenetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
But when his DNA was compared to that of other hunter-gatherers who lived west of Wallacea around the same time, his DNA did not contain any trace of Denisovan DNA.
“The geographic distribution of Denisovans and modern humans may have overlapped in the Wallacea region. It may be the key place where Denisovans and indigenous Australian and Papuan ancestors interbred,” Cosimo said in a statement. Posth, a co-author of the study and a professor at the Senckenberg Center for Human Evolution and Paleoenvironment at the University of Tübingen, in Frankfurt, Germany.
Researchers do not know what happened to the Toalean culture, and this latest discovery is one piece of the puzzle trying to understand the ancient genetic history of humans in Southeast Asia. Brumm hopes that more ancient DNA can be recovered from the Toalean people to reveal their diversity “and their broader ancestral history.”