Tibetan genetics: Life at the top

Thanks, great great great great great great great great great great great great grandad RESEARCHERS have known for a while that many people alive today carry genes from human species other than Homo sapiens--the result of ancient interbreeding with Neanderthals and Denisovans. They have even worked out that this admixed DNA must often be doing something particularly useful, because its pattern suggests natural selection is actively retaining it. The specifics, though, have not been clear. But in...