Numbers suggest mating with humans might have led to Neandertals’ demise

Scholars are turning the disappearance of humans’ closest cousins into a numbers game.

More than 150 years ago, German schoolteacher Johann Carl Fuhlrott realized that fossils from a local limestone quarry were almost, but not quite, human. More recently, scholars have expanded their research beyond bones and stones to figure out what became of the Neandertals.