The arrival of Europeans in the Americas resulted in what was perhaps the greatest demographic collapse in history. Racial mixing and changes to native production systems, social structures, and ideologies, though less quantifiable, played increasingly important roles in determining demographic trends. Demographic change among native peoples was strongly correlated with the intensity of Spanish immigration and settlement. The importation of African slaves was a response to the shortage of Indian labor, which derived from the absence of a substantial native population in pre-Columbian times or its decline in the early colonial period. The demographic impact of colonial rule was most devastating in the Caribbean, where most native groups became extinct within a generation. The end of the eighteenth century and the beginning of the nineteenth century was a watershed in the demographic history of Latin America. Colonization had not come to an end, and that many regions were still to experience its full demographic impact.