Jim Blaut, "Colonizer's Model of the World," pp. 183-186:
America became significant in the rise of Europe, and the rise of capitalism, soon after the first contact in 1492. Immediately a process began, and explosively enlarged, involving the destruction of American civilizations, the plunder of precious metals, the exploitation of labor, and the occupation of American lands by Europeans. If we are to understand the impact of all of this on Europe (and capitalism), we have to know how it occurred and why it happened so quickly--why, in a word, the conquest was successful.
There is a second crucial reason we need to understand the causality of the conquest. A nondiffusionist history starts all causal arguments with working assumption that Europeans had no innate superiority, in any dimension of culture, over non-Europeans, no a priori "higher potential" progress. This leads first to a recognition that Europeans in 1492 had special advantage over Asians and Africans, ideological, social, or material. But it demands that we make the same working hypothesis about human communities. Why, then, did Europeans discover America instead of Americans discovering Europe (or Africa, or Asia)? And why, after the first contact, did Europeans conquer the American civilizations instead of being defeated and driven from America's shores? The working assumption of cultural uniformitarianism--or, if you prefer, the psychic unity of humankind--here confronts the diffusionist tendency to dismiss the peoples of America as primitive and irrelevant.
There were several immediate reasons why American civilizations succumbed, but one of these is of paramount importance and probably constitutes a sufficient cause in and of itself. This is the massive depopulation caused by the pandemics of Eastern Hemisphere diseases that were introduced to America by Europeans. A second factor was the considerable advantage Europeans held in military technology, but this advantage has to be kept in perspective. The technological gap was not so great that it could by itself bring military victory--after the initial battles--against American armies that were vastly larger and would sooner or later have adopted the enemy's technology. America is a vast territory, and in 1492 it had a very large population, numbering at least 50 million people and conceivably as many as 200 million, a goodly proportion of these people living in state-organized societies with significant military capability. Military technology tends, historically, to diffuse from one camp to the opposing camp in a relatively short time. Moreover, the superiority of the Spaniards' primitive guns was not really very great when compared with the Americans' bows and arrows. I think it is, therefore, certain that the tide would have turned against the Europeans had the matter been merely one of military capability. There would have been no conquest, or the conquest would have embraced only a limited territory, and certainly would not have swept south as far as the great civilizations of the central Andes. The point is that history went in a different direction because of the incredibly severe and incredibly rapid impact of introduced diseases. Resistance collapsed because the Americans were dying in epidemics even before the battles were joined. Probably 90% of the population of central Mexico was wiped out during the sixteenth century; the majority of these deaths occurred early enough to assist the political conquest. Parallel processes took place in other parts of the hemisphere, especially where there were major concentrations of population, these in most cases being areas of state organization and high civilization. Perhaps three~quarters of the entire population of America was wiped out during that century. Millions died in battle with the Spaniards and Portuguese and in forced labor centers such as the mines of Mexico and Peru, but much greater numbers died in epidemics, and this was the reason that resistance to the conquest was rapidly overcome in most areas.
Both the susceptibility of American populations to Eastern Hemisphere diseases and the lower level of military technology among Western Hemisphere peoples can be explained in fairly straightforward cultural-evolutionary terms, although evidence bearing on the matter is partly indirect. The Western Hemisphere was not occupied by humans until very late in the Paleolithic period; there is dispute about the first arrivals, but scholars do not believe that the Americas were occupied before 30,000 B.P. The first immigrants did not possess agriculture. The earliest generations preceded the Agricultural Revolution in the Eastern Hemisphere; in addition, the source area for the migrations, northeastern Siberia, is generally too cold for agriculture, even for present-day agriculture, and we would not expect to find that these cultures were experiment--with incipient agriculture 20,000 years or so ago although some latitude cultures were doing so. Migrants to America were paleolithic hunters, gatherers, fishers, and shellfishers. They came in small numbers, apparently in a widely spaced series of relatively small population movements and spread throughout both North and South America. Only after some millennia had passed was the stock of resources for hunting, fishing, gathering, and shellfishing under any significant pressure from humans. One assumes that population growth was slow but--this is of course speculative--that population growth eventually did reach the point where conditions were favorable to an Agricultural Revolution. In the Eastern Hemisphere the Agricultural Revolution seems to have occurred (as a qualitative change) roughly 10,000-12,000 years ago. In the Western Hemisphere that point may have been reached about 4,000 years later. Thereafter, cultural evolution in the Western Hemisphere proceeded along lines somewhat parallel to those of Eastern Hemisphere evolution: the development of agricultural societies, of monumental ceremonial centers, science, writing, cities, feudal class structures, and mercantile trade. It seems, indeed, that the Western Hemisphere societies were closing the gap. But in 1492, military technology in the most advanced powerful states was still well behind that of Eastern Hemisphere states. Metal was just coming into use in this arena, and guns had not been invented. Hence the superiority of Cortes's armies over Moctezuma's and Pizzaro's over the Incas'. (When Cortes arrived at Tenochtithin the Aztecs already dying in great numbers from European diseases which, apparently, had been carried by American traders from Cuba to Mexico. Likewise, the Incas apparently were succumbing to these diseases before Pizzaro arrived.)
The susceptibility of American populations to Eastern Hemisphere diseases and the consequent devastation of American settlements, collapse of states, and defeat and subjugation by the Europeans, is explained in the same general model. Small populations entered America and ably bore with them only a small subset of the diseases that existed in Eastern Hemisphere at the rime of their departure. They came, in addition, from a rather isolated, thinly populated part of the hemisphere, and a part which, having a cold climate, would have lacked some diseases characteristic of warm regions. Perhaps more important is the history of the diseases themselves. Many diseases originated or became epidemiologically significant during or after the Agricultural Revolution, and have ecological connections to agriculture, to urbanization, to zoological and botanical changes in the ecosystems strongly modified by human land use, and so on. In the Eastern Hemisphere humanity entered these ecological situations after the initial migrations to the Western Hemisphere, hence these migrants to America would not have carried these diseases with them. Later migrants may have done so (although this is again unlikely because they came from a cold and isolated part of Asia, and came in small numbers). But we can assume that the sparse settlement, the hunting, gathering,-fishing, shellfishing way of life, and the absence of agricultural settlements and urbanization in the Americas during many millennia, would have caused a disappearance of some of the Eastern Hemisphere diseases that had been carried across to the Americas by migrants. After a time the American populations would have lost their physiological immunities to diseases no longer present in these populations, and they would of course lack immunities to diseases never before encountered. It is known, in this regard, that utter devastation was produced in the Americas from diseases to which Eastern Hemisphere populations had such high levels of immunity that they experienced these diseases as minor maladies only.
Hence there is no need to take seriously any longer the various myths that explain the defeat of the Americans in terms of imputed irrationality or superstitiousness or any of the other classical, often racist, myths about American civilizations in 1492. (The most widely known of these myths is the idea that Mexicans imagined that Cortes and his troops were gods, and fell down before them in awe instead of fighting. This did not happen.) The relatively minor difference in technology between the two communities, and the impact of Eastern Hemisphere diseases upon Western Hemisphere communities, can be explained in terms of the settlement history of the Western Hemisphere and its consequences. The Americans were not conquered: they were infected.
Louis Proyect (http://www.panix.com/~lnp3/marxism.html)