It's no surprise that modern humans and Neanderthals used to get it on—most people of Eurasian descent are, genetically, 1.6% to 2.1% Neanderthal. The question has long been when they did, with a wide estimate putting it between 37,000 and 86,000 years ago based on the DNA of people alive today. But now the complete genetic sequencing of a man's thigh bone, which is itself roughly 45,000 years old, suggests that we took a dip in the Neanderthal gene pool 50,000 to 60,000 years ago, reports National Geographic. The bone was found in 2008 in western Siberia; it's the oldest human bone to have been recovered beyond Africa and the Middle East.
"This is an amazing and shocking and unique sample," one geneticist and co-author of the study—published this week in the journal Nature—tells the New York Times. Because long stretches of DNA break into smaller ones over many generations, the researchers predicted that the Neanderthal DNA in the 45,000-year-old bone would be less fragmented than it is in us today, and they were right. By estimating the rate at which those DNA strands fragment, they came up with the interbreeding estimate of 50,000 to 60,000 years ago. (Earlier this year, better radiocarbon dating suggested Neanderthals died out earlier than we thought.)