Genetic signatures carried by present-day East Asians reveal that modern humans had intimate encounters with two separate groups of mysterious archaic humans called Denisovans.

Previous research showed that some early-modern humans living roughly 50,000 years ago had children with Denisovans, who are known only from a few teeth and a finger bone found in a Russian cave. To understand the results of this interbreeding, Sharon Browning at the University of Washington in Seattle and her colleagues surveyed thousands of contemporary human genomes, looking for the distinctive footprints of archaic DNA.

The researchers found that DNA from one set of Denisovans is found in present-day residents of Papua New Guinea and regions of east and south Asia. But many Chinese and Japanese people can also trace some of their ancestry to a second population of Denisovans. The DNA does not indicate which episode of interbreeding took place first.