Ancient humans had sex and interbred with a mysterious group known as the Denisovans more than once, new research has found

Wendy Stone/Corbis via Getty Images
  • We’ve known for a long time that early humans interbred with Neanderthals and Denisovans, other early hominin species that co-existed with Homo sapiens.
  • A new study indicates humans interbred with Denisovans more than once, showing that there were more interactions between these early hominin groups than we knew.
  • This helps show that we still have a long way to go in understanding the evolution and emergence of our own species, what would become modern humanity.

The more we learn about ancient human history, the more we see that Homo sapiens is not a unique species that stands apart from the rest of the evolutionary tree.

As our early ancestors spread around the globe and encountered other early hominin species like the Neanderthals, we interbred with them and had babies.

We’ve known for years now that early humans interbred with Neanderthals and Denisovans – other hominins that existed as early Homo sapiens were making their way out of Africa. Roughly 2% of the DNA in modern people from Europe and Asia comes from Neanderthals. Though we know less about the Denisovans and our interactions with them, up to 5% of the DNA of modern residents of Papua New Guinea show traces of interbreeding with Denisovans. Smaller traces of those ancient liaisons are found across Asia.

And a new study sheds even more light on the Denisovan connection. According to that research, humans didn’t just interbreed with Denisovans once – it happened at least twice.

We know very little about the Denisovans. Our knowledge comes from one set of ancient fossils discovered in the Altai mountains of Siberia. But the 2010 genetic sequence of that individual revealed these ancient hominins had left traces in modern humans, especially in Oceania.

Researchers from the University of Washington in Seattle wanted to better compare the genomes of modern humans and ancient Denisovans. To do so, they studied 5,600 whole-genome DNA sequences for people from Europe, Asia, America, and Oceania.

Denisovan homo sapienBrowning et al./CellThis graphical abstract shows two waves of Denisovan ancestry have shaped present-day humans.

“We analysed all of the genomes searching for sections of DNA that looked like they came from Denisovans,” said study senior author Sharon Browning, a professor of biostatistics at the University of Washington School of Public Health, in a news release.

They expected they’d find that most of the Denisovan DNA would trace back to that Oceania population from Papua.

“But in this new work with East Asians, we find a second set of Denisovan ancestry that we do not find in the South Asians and Papuans,” Browning said. “This Denisovan ancestry in East Asians seems to be something they acquired themselves.”

She thinks it’s possible that early humans in Oceania met and mated with a southern group of Denisovans around the same time the ancestors of modern East Asians encountered a northern group, all around 50,000 years ago.

This indicates that Denisovans may have been more widespread than we might have imagined based on this one fossil specimen we have. It seems they could have been widespread enough for separate groups of Homo sapiens and Denisovans to encounter and mate with each other in different places – and to do so enough that the genetic history of those encounters is still clear.

In recent years, we’ve learned that the first cave art in Europe was made by Neanderthals, not Homo sapiens. We’ve discovered the remains of previously unknown cousins of early humans, deep inside a cave in South Africa. There’s much we don’t know about the world we as a species emerged from.

And if anything, this helps demonstrate that our emergence – and our branch on the evolutionary tree – is less separate and unique from other early species than we may have thought.

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