An article recently appeared in Scientific American magazine about how humans conquered the planet.
Anatomically modern Homo sapiens appeared about 200,000 years ago, but for their first roughly 140,000 years were stuck in Africa. Then there was a rapid migration out into the Middle East, Europe, and Asia. Within the space of about 50,000 years — a mere blip in geological and evolutionary time — our kind had inhabited every major land mass on the planet except Antarctica, had wiped out all other hominid species such as the Neanderthals, and had hunted to extinction many large mammals, including the mammoths and mastodons.