More than 200 million years ago, geological forces split apart the continents. Isolated from each other, the two halves of the world developed radically different suites of plants and animals. When Christopher Columbus set foot in the Americas, he ended that separation at a stroke. Driven by the economic goal of establishing trade with China, he accidentally set off an ecological convulsion as European vessels carried thousands of species to new homes across the oceans.

The Columbian Exchange, as researchers call it, is the reason there are tomatoes in Italy, oranges in Florida, chocolates in Switzerland, and chili peppers in Thailand. More important, creatures the colonists knew nothing about hitched along for the ride. Earthworms, mosquitoes, and cockroaches; honeybees, dandelions, and African grasses; bacteria, fungi, and viruses; rats of every description—all of them rushed like eager tourists into lands that had never seen their like before, changing lives and landscapes across the planet.

Eight decades after Columbus, a Spaniard named Legazpi succeeded where Columbus had failed. He sailed west to establish continual trade with China, then the richest, most powerful country in the world. In Manila, a city Legazpi founded, silver from the Americas, mined by African and Indian slaves, was sold to Asians in return for silk for Europeans. It was the first time that goods and people from every corner of the globe were connected in a single worldwide exchange. Much as Columbus created a new world biologically, Legazpi and the Spanish empire he served created a new world economically.

As Charles C. Mann shows, the Columbian Exchange underlies much of subsequent human history. Presenting the latest research by ecologists, anthropologists, archaeologists, and historians, Mann shows how the creation of this worldwide network of ecological and economic exchange fostered the rise of Europe, devastated imperial China, convulsed Africa, and for two centuries made Mexico City—where Asia, Europe, and the new frontier of the Americas dynamically interacted—the center of the world. In such encounters, he uncovers the germ of today’s fiercest political disputes, from immigration to trade policy to culture wars.