Tibetan people can survive on the roof of the world—one of the most inhospitable places that anybody calls home—thanks to a version of a gene that they inherited from a group of extinct humans called Denisovans, who were only discovered four years ago thanks to 41,000-year-old DNA recovered from a couple of bones that would fit in your palm.  If any sentence can encapsulate why the study of human evolution has never been more exciting, it’s that one.

In 2010, Rasmus Nielsen from the University of California, Berkeley found that Tibetan people have a mutation in a gene called EPAS1, which helps them handle low levels of oxygen. Thanks to this mutation, they can cope with air that has