Watch the following video in which Hank and John Green teach you about humanity conquering the Earth. Or at least moving from Africa into the rest of the Earth. As human beings spread out across the world and populations grew, humanity reached a critical mass of innovators, and collective learning took off! All these innovations were great for lots of human endeavours, but none fared better than agriculture. 

You can find a transcript of this video below. It is not required reading but is helpful for review.

Migrations and Intensifications transcript