About 40,000 years ago, Neanderthals, who had lived for hundreds of thousands of years in the western part of the Eurasian continent, gave way to Homo sapiens, who had arrived from Africa. This replacement was not sudden, and the two species coexisted for a few millennia, resulting in the integration of Neanderthal DNA into the genome of Homo sapiens.
Click here for original story, The encounter between Neanderthals and Homo sapiens as told by their genomes
Source: Phys.org