Anthropologists have long puzzled over how much contact Neanderthals had with modern humans and when this may have occured.
Now, a genome taken from a 36,000-year-old skeleton has shed new light on the period of interbreeding between the two species.
The study of DNA recovered from a fossil of one of the earliest known Europeans - a man who lived in Russia - shows that the genes of the earliest inhabitants of the continent survived the Ice Age, helping sow the seed for the modern-day population.
The Kostenki genome revealed a small percentage of Neanderthal genes, confirming previous results that found Neanderthals and the first humans to leave Africa for Europe, briefly interbred.
Even today, everyone with Eurasian ancestry - from Chinese to Scandinavian and North American - has a small element of Neanderthal DNA.