Primates share food, but only Homo sapiens trades, William Bernstein says in this fascinating and well-written history. We merely traded blows with the Neanderthals, but after that we quickly grasped the concept of handing over something we had a surplus of in return for something we lacked. Early farmers, for instance, gave grain to hunter-gatherers in exchange for animal skins. And when you're used to hot and heavy animal skins or scratchy wool, just imagine how wonderful silk must have felt, Bernstein explains, who shows how trade has adapted to shifting tastes over the centuries, bringing consumers silk and spices, sugar and tea, but also opium, tobacco and slavery. And because trade requires control of shipping lanes it has also been a constant source of conflict and war. Plus it gave us the Black Death. In fact, trade always makes someone unhappy, concludes Bernstein. "Although free trade benefits mankind in the aggregate, it also produces losers who cannot be expected to passively accept the new order." He predicts crises ahead.