We are at the final frayed finish of the age of Europe's territorial expansion, which stimulates curiosity about its beginnings. The Social Darwinists were sure that white people were genetically superior to the other strains of humanity, and that was why they were such successful imperialists; at the end of the twentieth century that explanation seems as antiquated as a whalebone corset. Technological and managerial superiority are probably adequate to explain the brief subjugation of such lands as Algeria and Burma, but meagre when matched to the Europeans' much more thorough and seemingly permanent takeovers of the temperate regions of the Americas. The new right-off-the-shelf-and-ready-for-instant-use explanation is that the Amerindians, unlike Africans or Asians, died in huge numbers of Old World diseases carried for the first time across the Atlantic by Columbus and his emulators, and therefore were easily displaced and replaced by the invaders.

There is a large body of documentary evidence in support of this theory, but much of the evidence was collected in the pre-scientific and pre-statistical centuries and almost always by soldiers, missionaries, trappers and traders, rather than by physicians and demographers: i.e. it is no better than impressionistic. Furthermore, the enormous extent of the Americas, the number and variety of their aboriginal peoples and the length of time since the first contacts between the Old World invaders and the New World aborigines bring into question even the most obvious interpretations of what accounts we do have of the impact of exotic diseases on Amerindians.