When modern humans migrated from Africa around 60,000 years ago, a group of their descendants reached Australia around 10,000 years later. It had been assumed that they, and their DNA, remained isolated for 50,000 years until British colonists arrived in 1788. However, a new study has now found evidence that Australian Aborigines interbred with people from India around 4,200 years ago.
A team led by Mark Stoneking, a molecular anthropologist at the Max Planck Institute, tested the DNA of 344 people, including Aborigines from Australia’s Northern Territory, Australians with European ancestry, and people from Papua New Guinea, Southeast Asia, India and China. They found that Australian Aborigines, Papua New Guinea highlanders and the Mamanwa people from the Philippines were genetically the closest and they diverged around 36,000 years ago, when the Sunda and Sahul Shelves were still dry land. Much more surprising was the discovery of the more recent genetic mix with people from India, from which Australian Aborigines derive an estimated 11% of their DNA. Computer simulations estimated that the first interbreeding occurred 141 generations ago; at roughly 30 years per generation this dates back 4,230 years.
Stoneking said: “We have a pretty clear signal from looking at a large number of genetic markers from all across the genome that there was contact between India and Australia somewhere around 4,000 to 5,000 years ago.”
This date is significant because it also marks the first appearance of both microliths and dingoes in Australia. Microliths are fine stone tools found in archaeological sites all around the world, and it has been reasoned for some time that the dingo, a subspecies of the Indian grey wolf, is not native to Australia where all indigenous mammals are marsupials. Stoneking said: “We don’t have direct evidence of any connection, but it strongly suggestive that microliths, dingo and the movement of people were all connected.”
Neither is Stoneking sure how or where the genetic mixing between Indians and Australian Aborigines took place. It would be reasonable to assume that it happened on ‘neutral ground’ in Indonesia – except that no traces of Indian DNA could be found among the Indonesians sampled and no Indonesian DNA could be found in the Australians. This may suggest that the Indian migrants went directly to Australia by sea, without mixing en route.
This period of history coincides with the Indus Valley Civilization, which was at its height in northwest India between 2600 and 1900 BC. Their economy depended on trade and there is evidence that they had seagoing craft; archaeologists have found what appears to be a massive, dredged canal and docking facility at the coastal city of Lothal in western India. Other coastal settlements like Sutkagan Dor and Sokhta Koh grew around shallow harbours on river estuaries which opened into the sea. There is further evidence that their maritime trade network extended as far west as Egypt and the island of Crete. As such long-distance sea trade became feasible in the Bronze Age with the innovation of plank-built watercraft with masts supporting sails of woven rushes or cloth, an island-hopping sea-journey across the Indian Ocean to Australia should in theory have been within their capabilities.