Did the First Americans Actually Come From Australia?

Did the First Americans Actually Come From Australia?

A new study suggests that when hunters and gatherers crossed the ancient Bering Land Bridge that connected Asia to North America during the last Ice Age, they carried pieces of ancestral Australian DNA in their ancestral code.

Over the generations, they moved south, eventually making their way to South America. Even today, over 15,000 years after these people crossed the bridge, their descendants can be found in parts of the Sourth American Pacific coast, according to researchers. And they still carry ancestral Australian DNA.

“Much of this history has unfortunately been erased by the colonization process, but genetics is an ally to unravel unrecorded histories and populations,” study senior researcher and professor Tábita Hünemeier and study co-lead researcher and doctoral student Marcos Araújo Castro e Silva, both of whom are in the Department of Genetics and Evolutionary Biology at the University of São Paulo in Brazil, said in an email.

The new research builds on work that was published in 2015, which showed that ancient and modern Indigenous people in the Amazon shared specific genetic signatures — known as the Ypikuéra, or Y signal — with modern-day Indigenous groups in South Asia, Australia and Melanesia, a group of islands in Oceania. 

This genetic connection surprised many scientists. It remains “one of the most intriguing and poorly understood events in human history,” the researchers wrote in the new study.

To further investigate the Y signal, a team of scientists in Brazil and Spain looked at a large dataset containing the genetic data of 383 Indigenous people from different parts of South America. The team then used statistical methods to test whether any of the Native American populations had “excess” genetic similarity with a group they called the Australasians, or Indigenous peoples from Australia, Melanesia, New Guinea and the Andaman Islands in the Indian Ocean.

The researchers interpreted the South American groups that did have more genetic similarities with Australasians as being descendants of the first Americans and Australasian ancestors, who coupled together at least 15,000 years ago.

But the new genetic analysis revealed a big surprise: The Australasian connection was also found in Peru’s Chotuna people, an Indigenous group with ancestral ties to the Pacific Coast; the Guaraní Kaiowá, a group in central west Brazil; and the Xavánte, a group on the central Brazilian Plateau.

How did they get there?

The team believes that this ancestry came from people who crossed the Bering Land Bridge, probably from ancient coupling events between the ancestors of the first Americans and the ancestors of the Australasians “in Beringia, or even in Siberia as new evidence suggests,” Hünemeier and Araújo Castro e Silva said.

“What likely happened is that some individuals from the extreme southeastern region of Asia, that later originated the Oceanic populations, migrated to northeast Asia, and there had some contact with ancient Siberian and Beringians,” Araújo Castro e Silva said.

In other words, the Australasians’ ancestors coupled with the first Americans long before their descendants reached South America. “It is as if these genes had hitched a ride on the First American genomes,” Hünemeier and Araújo Castro e Silva said.