My argument is that this habit of exchanging, this appetite for barter, had somehow appeared in our African ancestors some time before 100,000 years ago. Why did human beings acquire a taste for barter as other animals did not? Perhaps it has something to do with cooking. Richard Wrangham makes a persuasive case that control of fire had a far-reaching effect on human evolution. Beyond making it safe to live on the ground, beyond liberating human ancestors to grow big brains on high-energy diets, cooking also predisposed human beings to swapping different kinds of food. And that maybe got them
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