Understanding the Denisovans means understanding ourselves

Today we are alone. But just a few hundred thousand years ago, our ancestors shared the world with at least five other ancient human species, including diminutive hobbits and burly Neanderthals.

It may now be time to add to that list. As we report in “An incredible Denisovan skull is upending the story of human evolution”, there are growing calls to give species status to a group of ancient humans known as the Denisovans.

This is hardly a rushed decision, given that the first Denisovan fossils were identified 15 years ago. Ancient DNA extracted from these remains revealed that they belonged to humans with a discrete evolutionary history. But it also suggested that these mysterious ancient people had interbred with our own ancestors, leaving many researchers reluctant to consider them a separate species.

However, some definitions of a species allow for interbreeding, as long as the species involved maintain a defined appearance. The problem was that we didn’t yet know what Denisovans looked like. But earlier this year, we learned that an unusually thickset ancient skull, unearthed in China, is associated with Denisovan DNA. With the confirmation that the Denisovans were distinct in appearance, it is easier to argue that they should be given a formal species name.

Biologists’ desire to divide nature up into species is sometimes dismissed as mere stamp collecting, where the aim is to categorise organisms rather than truly understand them. But in this case, at least, there is value to the exercise. Anatomical evidence from the Denisovan fossils points to the intriguing possibility that these enigmatic humans were very closely related to our species – perhaps, in fact, more closely related than any other. That suggests we might gain a particularly clear insight into the early behavioural development of Homo sapiens by comparing them with the Denisovans.

At some point, our ancestors learned new behaviours that helped them outcompete all other human species. It is just possible that the Denisovans could help us work out how we came to be the last humans standing.