Neanderthal and human interbreeding, illustration. Neanderthals (pregnant female at right) were shorter and more heavily built than modern humans (male at left), who are taller and slenderer. Neanderthals (Homo neanderthalensis) first appeared in Europe around 600,000 years ago, and co-existed with modern humans (Homo sapiens), who emerged around 200,000 years ago. It is thought that Neanderthals and modern humans interbred, and by around 30,000 years ago no Neanderthal traits remained.