In 2015, a cave in Indonesia found the remains of an ancient woman's skeleton. It is believed that she has ancestry like no other human. Archaeologists now have a rare glimpse at the first settlers to leave the mainland Asia to begin their journey to New Guinea or Australia.
Bess, a 7,200-year-old human, was part of a culture known as Toaleans. They are thought to be related to the first settlers of Indonesia. The Toaleans' ancestors arrived from mainland Asia via sea at least 65,000 years ago during the last ice ages.
Although the Toalean culture didn't seem to have made it past Sulawesi on the Indonesian Island, it appears that their descendants continued to push forward.
This is what the inner ear bone from this Toalean woman indicates. Her ancient skull now contains the first known human DNA found in Wallacea, an ancient island that was once a gateway to New Guinea or Australia.
This map shows the location of Wallacea as well as where Bess was discovered. (Carlhoff et al., Nature, 2021)
Adam Brumm, an archaeologist from Griffith University in Australia, says that these seafaring hunters-gatherers were the earliest inhabitants Sahul. This supercontinent was formed during the Pleistocene, (Ice Age), when global sea levels dropped. It opened up a land bridge connecting Australia and New Guinea.
"To reach Sahul these pioneering people crossed the ocean through Wallacea to reach their destination. But little is known about their journeys."
Archaeologists debate today where the Toaleans came from and when they arrived at Wallacea. It is possible that the few artifacts and tools from their long-ago culture are only found on a small portion of the Indonesian island. This suggests that the culture was isolated and small.
One of the few remaining pieces of evidence is the skull of Bess. A careful genomic analysis revealed that this 17--18-year-old Toalean Forager is genetically different from all other early humans. It appears she is an ancient in-betweener, stuck on an island between two supercontinents.
Bess shares approximately half of her genetic makeup with Indigenous Australians as well as people from New Guinea, the Western Pacific islands and others, which suggests that her ancestors kept island-hopping past Sulawesi.
Bess has no known ancestry to modern islanders. According to researchers, the Neolithic farmers of what is now Taiwan replaced the small Sulawesi culture around 3,500 years ago. The society was a mere memory by the 5th Century CE.
"The discovery and implications of Bess' genetic ancestry shows just how little we know about the early human story of our region and how much we still have to discover," says Brumm.
The Toalean woman, for example, appears to have significant Denisovan ancestry. This is similar to the cross-over of Neanderthals with modern Europeans.
This gene mixing occurred either before or after the settlement of Wallacea, on the mainland.
Another island near Sulawesi has revealed evidence of ancient hunter-gatherers without any Denisovan ancestry. This suggests that Sulawesi, or another Wallacean island, might have been an important place where archaic as well as modern humans mingled their genes.
The authors write that "the apparent presence of an archaic hominin population in southwestern Sulawesi is a possible source of the introgression event."
"Two studies in the past have indicated that two divergent Denisovan lines mingled into the ancestors Papuan individuals. However, our genomic data do not allow us to differentiate between one or more introgression pulses.
According to what we know, the ancestors of Papua New Guinea have a lower percentage of Denisovan-derived genetics than the Toalean woman. This indicates that Denisovan genetics became less valuable as humans moved away from Asia.
This is just one idea. Before we can properly trace the history and migration of humans across Asia Pacific, we need more genetic evidence.
Bess was, in fact, just one woman.
Nature published the study.