Charles C. Mann has faced up to the locavore’s dilemma. At his home in the Berkshires, he likes to eat food that has traveled directly from his own garden: heirloom tomatoes, eggplant, bell peppers, kale, chard, lettuce and other foods for his table. He and his family belong to a farm-share program in which they advance money each year to a farmer a few miles away in return for the farm’s crops. He loves local food, but he knows too much about it to be a truly devout locavore.

Mr. Mann realizes that none of the foods in his garden or at the local farm originated within 1,000 miles of his home. They grow today in the Berkshires only because of farmers and plant breeders and traders throughout the world. While today’s locavores worry about the sustainability of the globalized modern system of agriculture, Mr. Mann sees today’s food system as nothing new.

The foods we consider local are results of a globalization process that has been in full swing for more than five centuries, ever since Columbus landed in the New World. Suddenly all the continents were linked, mixing plants and animals that had evolved separately since the breakup of the ancient supercontinent Pangaea.

What resulted, Mr. Mann argues in his fascinating new book, “1493: Uncovering the New World Columbus Created,” was a new epoch in human life, the Homogenocene. This age of homogeneity was brought on by the creation of a world-spanning economic system as crops, worms, parasites and people traveled among Europe, the Americas, Africa and Asia — the Columbian Exchange, as it was dubbed by the geographer Alfred W. Crosby.