Roaming Romania 40,000 years ago was a modern human with a family tree that recently surprised scientists. Researchers figured out that this fellow could have had a great-great-grandparent that was a Neanderthal. In fact, genomic sequencing of the ancient jawbone specimen indicated that six to nine percent of the man’s DNA was Neanderthal. That’s the most Neanderthal DNA found in a modern human yet, says David Reich, professor of genetics at Harvard Medical School and an author of the paper about the findings, published this week in Nature. Reich explains what this discovery helps us understand about the early interactions between Neanderthals and modern humans in Europe.