Ancestry traced to founding population

Indigenous Australians descended from common ancestors who lived 10,000 to 32,000 years ago, a genetic study shows.

The first-of-its-kind study, published today in the journal Nature, describes genomic findings from 83 Aboriginal Australians from the Pama-Nyungan language group and 25 Papuans from the New Guinea Highlands.

Evolutionary geneticist Eske Willerslev at the University of Copenhagen in Denmark and colleagues found ancestors of both groups diverged from Eurasian populations around 58,000 years ago during the same dispersal from Africa, with Indigenous Australians’ founding population living around 37,000 years ago.

The migration story of our human ancestors is hotly debated. Some camps believe we all descended from one population out of Africa, while others argue that distinct waves of population movement divided us into separate genetic lineages.

As genome sequencing becomes easier and more accessible, enormous banks of genetic information are coming to light. Willerslev and his crew collected saliva samples from Indigenous Australians and Highland Papuans and delved into their genome.

“The distinctiveness of the Australian archaeological and fossil record has led to the suggestion that the ancestors of Aboriginal Australians and Papuans left the African continent earlier than the ancestors of present-day Eurasians,” the researchers explain.

“We find that Aboriginal Australians and Eurasians share genomic signatures of an Out-of-Africa dispersal – a common African ancestor, a bottleneck and a primary pulse of Neanderthal admixture.”

The researchers add that Aboriginal Australians show links to Eurasian humans and hominins, including the ancient Denisovan group and another archaic hominin not yet known to science.

Genetic details also give glimpses into Aboriginal society. For instance, genes inherited from the mother’s side differ more greatly between groups than genes on the father’s Y chromosome, in contrast to most human populations.

This, the researchers say, suggests “higher levels of male- than female-mediated migration, and may reflect the complex marriage and post-marital residence patterns among Pama–Nyungan Australian groups”.

The paper is published alongside a larger study which analysed 300 genomes from 142 diverse populations, homing in on groups underrepresented in existing research.

This study, also published in Nature, suggests that the rate of genetic mutations among non-African populations has increased by 5% since diverging from African populations. 

The findings support the case that human populations had significantly separated by around 100,000 years ago and emerged from distinct migration waves out of Africa.

“The high-resolution portrait of human genetic diversity afforded by these studies allows new inferences to be made about our migration out of Africa,” the University of Washington’s Serena Tucci and Joshua Akey write in a News and Views article.

“Although these studies fill in some missing pieces in the puzzle of human history, many fascinating questions remain […] to fully retrace the steps taken by our ancestors as they explored and colonised the world.”