To shed light on the archipelago’s settlement history, researchers sequenced and analyzed sixteen ancient genomes
The Wallacean islands of present-day Eastern Indonesia have a long history of occupation by modern humans. Notably, the maritime expansion of Austronesian speakers into Wallacea left archaeological traces of a Neolithic lifestyle and a genetic imprint still detectable in Eastern Indonesians today. To gain further insights into Wallacea’s settlement history, an international team of scientists led by the Max Planck Institutes for Evolutionary Anthropology (Leipzig), the Science of Human History (Jena) and the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen sequenced and analyzed sixteen ancient genomes from different islands of Wallacea, finding evidence for repeated genetic admixtures starting at least 3,000 years ago. Those contacts involved multiple distinct groups from neighboring regions of Asia and Oceania.
To shed light on the details of this expansion and the resulting human interactions, an international team of researchers analyzed DNA from 16 ancient individuals from different islands in Wallacea, greatly increasing the amount of ancient genomic data representing this region. “We found striking differences between regions in Wallacea and surprisingly, the ancestry of ancient individuals from the southern islands cannot be simply explained by admixture between Austronesian- and Papuan-related groups,” says Sandra Oliveira, one of the study’s lead authors.
Early ancestry contribution from Mainland Southeast Asia
The team identified an additional ancestry contribution from Mainland Southeast Asia, closest to present-day Austroasiatic speakers, and proposed that admixture occurred first between the Mainland Southeast Asian and Papuan-related ancestry and that gene flow from Austronesian-related groups occurred only later. “That Mainland Southeast Asian component is a great mystery to me. I suspect that we might be looking at small groups, perhaps of early farmers, who travelled a long way, left no archaeological or linguistic traces along the way, but who increased their population sizes after arrival,” says Peter Bellwood, an author of the study who has conducted archaeological work in Island Southeast Asia for decades.
While the identity of the people who spread this ancestry is still unclear, the discovery of the Mainland Southeast Asian ancestry and its possible antiquity in the southern Wallacean islands has major implications for the understanding of the Neolithic dispersals into Island Southeast Asia. “This finding is very important for the archaeologists in the region,” adds Toetik Koesbardiati, an Indonesian Anthropologist (Universitas Airlangga) involved in the study. He adds, “We will certainly intensify our efforts to study this migration with other lines of evidence.”
Multiple admixture events throughout Wallacea
Local hunter-gatherers’ genetic ancestry was largely replaced
The team also searched for genetic similarities between the newly reported ancient Wallaceans and a previously published pre-Neolithic individual from Sulawesi, another island in Wallacea. “All Wallacean individuals sequenced in this study are more similar to present-day New Guinean groups than to the earlier local population, suggesting that these two regions were more closely connected in ancient times than previously imagined,” says Cosimo Posth, another senior author of the study. He concludes, “These results also confirm that the genetic ancestry of Wallacean hunter-gatherers has been largely replaced.”
Original publication:
Sandra Oliveira, Kathrin Nägele, Selina Carlhoff, Irina Pugach, Toetik Koesbardiati, Alexan-der Hübner, Matthias Meyer, Adhi Agus Oktaviana, Masami Takenaka, Chiaki Katagiri, Del-ta Bayu Murti, Rizky Sugianto Putri, Mahirta, Fiona Petchey, Thomas Higham, Charles F. W. Higham, Sue O’Connor, Stuart Hawkins, Rebecca Kinaston, Peter Bellwood, Rintaro Ono, Adam Powell, Johannes Krause, Cosimo Posth and Mark Stoneking: Ancient ge-nomes from the last three millennia support multiple human dispersals into Wallacea. Nature Ecology and Evolution, https://doi.org/10.1038/s41559-022-01775-2
