A massive genomic study of Indigenous peoples in the Americas has uncovered evidence of a previously unknown migration into South America that occurred as recently as 1,300 years ago – during China’s Tang dynasty.

These new settlers carried genes remarkably similar to Indigenous populations in what is now Australia and the Pacific Islands, according to the study published online by the journal Nature on April 22.

The international team, which included scientists from the University of Sao Paulo and Spain’s Spanish National Research Council, analysed 128 newly-sequenced Indigenous American genomes together with ancient DNA samples from across the Americas.

The researchers concluded that much of the ancestry found in modern Indigenous South Americans did not come primarily from the continent’s earliest settlers. The precise origin of these new migrants remained uncertain, they said.

The team stressed that the findings did not imply a direct migration from Australasia to South America but instead pointed to an ancient “ghost population” that contributed genetic ancestry to some Indigenous groups in the Amazon.

For decades, scientists have believed that the Americas were populated through two major migration waves of ancestral groups that began roughly 15,000 years ago across a land bridge that once existed in the Bering Strait between today’s Alaska and Siberia.