This doesn't mean there were no people living in the rest of the world at that time. It's just a schematic to understand where the poles of power have been.

Alexander the Great tried to frontrun everyone and he was very close to fool his contemporaries. He was welcomed with open arms in Egypt despite the fact that he was the occupier. He was schooled by Aristotle and the Greeks really knew their stuff. The Roman Empire wouldn't have existed without the Greek wisdom.