The migration of the modern human population to Papua Island has occurred since 50 thousand years ago by crossing the islands in the Wallacea zone. However, due to the lack of archaeological remains, the aftermath is not widely known and is still a mystery.
Gludhug A Purnomo, a PhD candidate at Adelaide University in Australia, explained that about 50-60 thousand years ago, the mainland of Papua and Australia were still joined, called the Sahul (Australia and New Guinea) exposure. Opposite the Sahul shelf, there is Sundaland or the Sunda shelf (SE Asia and Island SE Asia). Then in between the two, there is such a thing as the Wallacea zone.
"There is an area that is not part of Sahul or Sunda, called the Wallacea zone, and this is a geographical barrier. The flora and fauna in this region are certainly different and interesting. The question is what about human life at that time," said Gludhug in the webinar "Unraveling the Mysteries The Origin of Our Ancestors" held by BRIN and MRIN, Tuesday (2/8/2022).
The Wallacea region which includes Sulawesi, the Maluku Islands and North Maluku, as well as East Nusa Tenggara are known as islands that have never joined the mainland.
This archipelagic zone surrounded by ancient waters separates Sundaland, namely Sumatra, Java and Kalimantan which is integrated with mainland Asia, with the Sahul Shelf covering Papua and Australia which were still united when sea level reached its lowest point about 50 thousand years ago.
Based on genetic studies conducted by Gludhug, there was extensive genetic pattern change in the Wallacea zone about 15,000 years ago and 3,000 years ago, due to the arrival of new groups of migrants.
This study on settlements in Wallacea and Papua was published by Gludhug and his international team in the journal Genes on June 24, 2021. Gludhug was the first author of this article and there were other authors, namely Prof. dr. Herawati Sudoyo, PhD, principal researcher at the Mochtar Riady Institute for Nanotechnology (MRIN).
A number of archaeological evidences in Australia have found fossils of modern humans (Homo sapiens) from Africa that are about 50 thousand years old. This triggers the hypothesis that in that period, humans had crossed the Wallacea zone to Papua, which at that time was still part of the Sahul Shelf.
"However, research on population history in Wallacea is very limited. Our current focus is on the Wallace zone which includes Sulawesi, Maluku, Aru, and others," he said.
Prof. Dr. Herawati Sudoyo, PhD said that the paleogenomic approach could help unravel this mystery. Paleogenomics is a field of science that studies genetic material derived from the remains of ancient organisms in the past.
According to Herawati, reconstruction of the history of settlement of islands in Indonesia using a genetic approach will help infer time of arrival, population size, and historical fluctuations, as well as migration patterns and resulting mixing rates.
"With genomic data, we can get an overview of genomic mixing, see the larger spatial and region of the archipelago. We can also compare it with non-genomic data such as language, archeology and history. We can learn many things about the impact of the mixing process, " he said.
Gludug and his team's study found a dynamic population history in Wallacea, characterized by two periods of extensive demographic change concentrated around the Last Glacial Maximum about 15,000 years ago and post-Austronesian contact about 3,000 years ago.
This finding, according to Gludug, shows that there are three waves of settlement in the Wallacea area. First, during migration 50,000 years ago, some of which then continued their journey to Papua and Australia. Second, the period is about 15 thousand years ago, and the third is about 3 thousand years ago. He also mentioned that there was a possibility of back-migration from Papua to Wallacea.
"We also found an Austronesian mix in the current Papuan population, for example in Sorong, West Papua which has an Austronesian genetic mix of around 40% and in Keerom about 6%." he explained.