Neanderthals probably suffered from psoriasis. They were susceptible to Crohn’s disease. They appear to have been capable of producing abstract designs. They made tools out of bone and, quite possibly, decorations out of feathers. These are some of the latest findings on our beetle-browed relatives—the studies seem to be arriving every few weeks now—and they’ve had the unsettling effect of making them seem ever more like us.

It is no longer news that Neanderthals and modern humans were similar enough to interbreed. That discovery made headlines worldwide when it was first announced, in the spring of 2010, by a team of scientists at the Max Planck Institute for Evolutionary Anthropology, in Leipzig. “Humans and Neanderthals: Getting It On, After All,” a typical one read. (I wrote about the lead scientist responsible for this discovery, Svante Pääbo, in 2011.)

This “getting it on” left a lasting mark: even today, all non-Africans retain bits of Neanderthal DNA.

Research published last year indicates that human-Neanderthal couplings were rare, and that the offspring they produced had fertility problems. This, in turn, suggests that Neanderthals were not so closely related to modern humans as to count as members of the same species. (Other recent research suggests that susceptibility to psoriasis and Crohn’s disease can be traced back to the common ancestor of humans and Neanderthals, and are traits shared by both species.)

The finding that the products of human-Neanderthal romance (or, just as likely, rape) had fertility problems is not surprising: many hybrid creatures have trouble reproducing. At the same time, it makes the question of why so many of us still possess traces of the Neanderthal genome that much more intriguing. For the genetic results to make sense, modern humans must have interbred with Neanderthals after they migrated out of Africa but before they spread into Europe and Asia. Were certain bits of Neanderthal DNA in some way useful to people as they migrated into new climates and new terrains?