A man who lived between 37,000 and 42,000 years ago in Romania probably had a great-great-grandparent who was Neanderthal, according to a new paper in the journal Nature.

Researchers have sequenced the DNA from the man, who was an early modern human, and discovered that between 6 percent and 9.4 percent of his genome comes from Neanderthals. That’s more Neanderthal DNA than any other modern human we’ve analyzed so far. “It could be four to six generations back,” says Qiaomei Fu, a paleogenomicist at Harvard Medical School. “It’s almost like this guy can touch the Neanderthal. So this is amazing.”

Fu and her team based the analysis on DNA extracted from a jawbone discovered in 2002 in a Romanian cave called Peștera cu Oase (thus the subject’s name, Oase 1). “The only access to the cave is by scuba diving through an underground river,” Erik Trinkaus, a palaeoanthropologist at Washington University in St. Louis, Missouri, told Nature.

Oase 1 would have looked at least a little Neanderthal. Anatomically speaking, his jaw had both early human and Neanderthal features, including abnormally large wisdom teeth. Using a dentistry drill, Fu and her colleagues collected powder from his jawbone. “We saw really, really large chunks” of Neanderthal DNA in his genome, Fu says.

Oase 1 was one of the earliest modern human residents of Europe, which the Neanderthals had called home at least 300,000 years ago. They started to die off about 40,000 years ago as people like Oase 1 moved in. We've known for several years that these two versions of early humans interbred. Any human living today with non-African heritage carries some Neanderthal DNA—between 1 percent and 4 percent of their genome. Oase 1 carries double to triple that amount. 

It isn't clear when and where this interbreeding began. The most common theory is that we mated with Neanderthals in the Middle East as we migrated out of Africa, some 50,000 years ago. Oase 1's remains show that Neanderthals and modern humans mixed in Europe too, and far more recently—even as Neanderthals as a whole were dying out.

“The fact that the Oase 1 individual had a Neanderthal ancestor removed by only four to six generations allows this Neanderthal admixture to be dated to less than 200 years before the time he lived,” the authors write.

It's unlikely Oase 1 has any living relatives, they say. He doesn't bear more of a genetic likeness to later Europeans than he does to East Asians, which suggests that the population group he came from didn't contribute their genes to more recent inhabitants of Europe. “This guy might just be one part of the migration and doesn’t have descendants,” Fu says.

Further genetic research on early humans—modern, Neanderthal, or other—could clarify the picture. “We currently only have several early modern human genome-wide studies,” Fu says, “so it would be great to know more so we can understand better for our own history.”