Neanderthals, one of the last extant hominid species other than our own, left Africa somewhere between 400,000 and 800,000 years ago and settled mostly in Europe until they went extinct 30,000 years ago. Early modern humans left Africa about 80,000 to 50,000 years ago, meaning they overlapped with Neanderthals in time and place for at least 20,000 years. On an evolutionary time scale, that's not a ton of time, but could it be enough to leave lasting evidence of human/Neanderthal interbreeding?
According to Dr. Labuda, the answer is an emphatic "yes." Back in the early '00s, he and his team had identified a particular piece of DNA in the human X chromosome that seemed out of place with everything else, and they wondered whether it might have originated from a non-human source.
That answer came with the first sequencing of the Neanderthal genome last year. Dr. Labuda compared 6,000 chromosomes from all over the world to the corresponding part of the Neanderthal sequence. With the exception of people from sub-Saharan Africa - whose ancestors would have been unlikely to come into contact with Neanderthals, since their territories didn't overlap - every chromosome featured evidence of the Neanderthal sequence.
Might help explain why the Republican party has a mastodon as its symbol.