The divide between their lineage and ours narrowed even further in 2010, when researchers published the first Neandertal genome sequence. Comparison of that ancient DNA with modern human DNA showed that the two species had interbred and that people today still carry the genetic fingerprint of that intermixing. Since then, numerous studies have explored the ways in which Neandertal DNA affects our modern physiology, revolutionizing our understanding not only of our extinct cousins but of ourselves as a hybrid species.

This area of research, clinical paleogenomics, is still in its infancy, and there are many complexities to unravel as we explore this new frontier. We therefore must take the findings from these studies with a grain of salt. Nevertheless, the research conducted to date raises the fascinating possibility that Neandertal DNA has wide-­reach­ing effects on our species—not only on general health but on brain development, including our propensity for conditions such as autism. In other words, DNA from our extinct relatives may, to some extent, shape the cognition of people today.