On May 21, 2024, an analysis of ancient and modern genomes suggested contemporary people’s Neanderthal DNA came from a single, prolonged period of mixing some 47,000 years ago. Most people of European ancestry alive today carry traces of genes inherited from Neanderthals—the enduring legacy of prehistoric hookups with our extinct cousins. But researchers have long debated when and where that mingling happened, and whether these were one-off romps or commonplace trysts.

The researchers concluded in the that Neanderthal genes began flowing into the ancestors of people alive today about 47,000 years ago. Modeling shorter and longer periods of gene flow, they found that a scenario in which Neanderthals and modern humans exchanged genes over a period of about 6000 to 7000 years best fit the data. The findings were published in a bioRxiv preprint.