Old world germs were entities having size, weight, and mass, just like Sweet Betsy, her Ike, and their animals; germs required transportation across the oceans, which the marinheiros unintentionally supplied. Once ashore and lodged in the bodies of new victims in new lands, their rate of reproduction (as often as every twenty minutes) enabled them to outperform all larger immigrants in rapidity of increase and speed of geographical expansion. Pathogens are among the “weediest” of organisms. We must examine the colonial histories of Old World pathogens, because their success provides the most spectacular example of the power of the biogeographical realities that underlay the success of European imperialists overseas. It was their germs, not these imperialists themselves, for all their brutality and callousness, that were chiefly responsible for sweeping aside the indigenes and opening the Neo-Europes to demographic takeover.