New Delhi: Australia’s native aboriginal population may have partly been made up of an Indian diaspora that brought with it Stone Age and early plant-processing technologies as well as the dingo, says a new study based on gene-mapping.
This potentially complicates the current scientific understanding of how humans spread out of Africa to the rest of the world. The existing consensus is that Australia was isolated for almost 45,000 years following its initial colonization by early humans of African origin, until it was discovered bv James Cook in 1770 and subsequently colonized by the British.
The new study suggests that around 4,000 years ago—about when the urbanized civilization at Harappa was on its decline in North India—a group of Indians almost certainly settled in northern Australia.
The study, which appears in the peer-reviewed Proceedings of the National Academy of Sciences, is a result of researchers at the Max Planck Institute for Evolutionary Anthropology, Germany, combing through the DNA of 344 individuals, including lineages as diverse as the Han Chinese, Papua New Guineans and South Indians.
“Australian archaeological record documents some changes which occur in Australia around 4,000 years ago,” said Irina Pugach, one of the authors of the study, in an email. “Our contribution to this debate is that we were able to show, for the first time, with genome-wide genetic data, that Australia did experience some gene flow around 4,000 years ago, and that the source population was closely related to the present-day Dravidian-speaking Indian groups.”
To better understand these prehistoric human migrations, Pugach and her colleagues looked at genomes of modern humans and tried to identify regions of DNA called “ancestry” blocks created by a process of genetic recombination.
Since this process repeats itself every generation, DNA molecules get chopped into progressively smaller pieces; measuring the width of these “ancestry” blocks and relating it to the time since migration gives an accurate estimate of when specific populations diverged from one another.
The expansion of modern humans apparently proceeded via two routes: the northern dispersal that gave rise to modern Asians 23,000–38,000 years ago, and an earlier southern dispersal that followed the coast around the Arabian Peninsula and India to the Australian continent.
Scientists currently believe the ancestors of aboriginal Australians and Papua New Guineans diverged from ancestral Eurasian population 62,000–75,000 years ago and, based on archaeological evidence, reached Sahul (then a joint Australia–New Guinea land mass) at least 45,000 years ago.
Pugach said her work was part of a larger project to trace, using DNA marking tools, the spread of the early human race and its interaction with a race called the Denisovan. Like the Neanderthal, the Denisovan were close cousins of the human species who, it’s believed, exterminated them from Europe and South East Asia, respectively.
“One of the questions we are interested in exploring in the future is the signal of ancient admixture evident in the genomes of aboriginal Australians and Papua New Guineans from the ancient hominins knows as the Denisovan,” said Pugach. “If we succeed, we’ll be able to answer questions about the first human colonization of SE Asia and greater Australia, and potentially even pinpoint the route followed by early modern humans out of Africa.”