There could be several answers to this one question but, the one that I'll talk about is the Move from Africa out to the way points of Europe and the East.
When man, as we knew him moved for whatever reasons, drought, food, following herds, moved into the stages that brought him towards the destiny of where we are today, the European Continent and the Asian Continent.
There will be those that will argue about Parallel movement and I agree, until we know for sure this may have happen but for now ?