Native Amazonians have been the victims of two massive historical assaults, one at the time of the Conquest and the other during the Twentieth century. Due to epidemic disease and environmental destruction, many tribes have gone from contact to displacement, decimation, and extinction in a single generation. Deculturation and the construction of large development projects have had catastrophic effects on native populations. In many ways, native Amazonians have experienced a reverse of the "Epidemiologic Transition". Paradoxically, one of the effects of cultural disruption for some native Amazonians has been the loss of cultural controls on fertility with the result that high fertility has become a major health problem. Combined with rapid growth of non-indigenous Amazonian populations, deforestation, and urbanization, native Amazonians face grave obstacles to long-term survival.