Right, so it was Alfred Crosby Jr., and in that book he wrote, The big questions are really the only ones worth considering, and colossal nerve has always been a prerequisite for such consideration. I love it! Before 1492, we couldn't really talk about a world history at all, we could only talk about the different histories of separate regions, but Columbus changed all of that, and everything else. The Columbian Exchange irrevocably homogenized the world's biological landscape. Since Columbus, the number of plant and animal species has continually diminished, and the variation in species from place to place has diminished dramatically. I mean, the first European visitors to the Americas had never seen a tomato or a catfish, Native Americans had never seen a horse. And by making our planet biologically singular, the Columbian Exchange completely remade the populations of animals, particularly humans.