Homo sapiens aren’t as unique as we once thought. In fact, only about 1.5 to 7 per cent of our DNA originated in our species alone. Everything else we share with our ancestors and those human species we once coexisted with, including Neanderthals, Denisovans and even some yet-to-be-identified “ghost populations”. This rewrites the story we have told ourselves about our species. We just aren’t that unique.

When our ancestors met these other human species, they didn’t just compete with them: they mated with them. And those encounters left a permanent record in our DNA. In other words, those ancient humans we thought had vanished didn’t necessarily disappear… Some of them are still here inside you.

Read more: How Homo naledi is changing what we know about death

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Who were the other humans, and why did we outlast them all? This marathon takes a single provocative question and follows it across three acts: the species we shared the planet with; the most mysterious of our lost cousins; and the moment we challenge everything we thought we knew about our own story.

Denisovans were an enigmatic human species that, until recently, had only been identified thanks to DNA from fragmentary fossils, including a finger and a jaw bone.

More recently, a spectacular skull found in Harbin, China, has enabled us to put a face to this mysterious species and potentially give the Denisovans a new name: Homo longi, or Dragon Man. But it didn’t stop there. Three more skulls uncovered in Yunxian, China, are upending everything we know about human evolution. These 1-million-year-old artefacts offer a tantilising hint that Homo sapiens may be much older than previously thought and suggest we may be looking in the wrong time and place to find Ancestor X, the relative that modern humans, Neanderthals and Denisovans all decend from.

Join paleoanthropologist, Ella al-Shamahi as we explore the story of Denisovans and how they are changing everything we know about human evolution.

Read more: Hominin fossils from Morocco may be close ancestors of modern humans

In 2010, DNA analysis of a 40,000-year-old finger bone revealed that it came from a previously unknown group of ancient humans, dubbed the Denisovans after the cave in Siberia where the bone was found. Since then, Denisovan DNA has been found in a skull discovered in China, and other, older skulls have been found.  The mystery of the Denisovans is starting to unravel. In this interview, paleoanthropologist Chris Stringer at the Natural History Museum in London explores what we know about Denisovans and what they tell us about our own family tree.

An ancient skull has finally shown us what the Denisovans looked like. Now it turns out they, not Neanderthals, might be our closest relatives, redrawing our family tree and transforming the hunt for Ancestor X.