Spanish conquest of the Inca Empire
Effects of the conquest on the people of Peru

The long-term effects of the arrival of the Spanish on the population of South America were catastrophic. While this was the case for every group of Native-Americans invaded by Europeans during this time period, the Inca population suffered an exceptionally dramatic and rapid decline following contact. The population decline for the Inca Empire from 1520 to 1571 is roughly estimated at from 10 to 12 million in 1520 to less than 3 million in 1570 with the population still declining after 1570.

The single greatest cause of the decimation of native populations was Old World infectious diseases, carried by colonists and conquistadors. As these were new to the natives, they had no acquired immunity and suffered very high rates of death. More died of disease than any army or armed conflict. As the Inca did not have as strong a writing tradition as the Aztec or Maya, it is difficult for historians to estimate population decline or any events after conquest. But, it is sometimes argued, and equally disputed among scholars that the Inca began to contract these diseases several years before the Spanish appeared in the region, as it was possibly carried to their empire by traders and travelers. The outbreak, argued to be hemorrhagic smallpox, reached the Andes in 1524. While numbers are unavailable, Spanish records indicate that the population was so devastated by disease that they could hardly resist the foreign forces.

Historians differ as to whether the illness of the 1520s was smallpox; a minority of scholars claim that the epidemic was due to an indigenous illness called Carrion's disease. In any case, a 1981 study by N. D. Cook the shows that the Andes suffered from three separate population declines during colonization. The first was of 30–50 percent during the first outbreak of smallpox. When a measles outbreak occurred, there was another decline of 25–30 percent. Finally, when smallpox and measles epidemics occurred together, which occurred from 1585 to 1591, a decline of 30–60 percent occurred. Collectively these declines amounted to a decline of 93 percent from the pre-contact population in the Andes region. Mortality was particularly high among children, ensuring that the impact of the epidemics would extend to the next generation.

Beyond the devastation of the local populations by disease, they suffered considerable enslavement, pillaging and destruction from warfare. The Spanish took thousands of women from the local natives to use as servants and concubines. As Pizarro and his men took over portions of South America, they plundered and enslaved countless people. Some local populations entered into vassalage willingly, to defeat the Inca. Native groups such as the Huanca, Cañari, Chanka, and Chachapoya fought alongside the Spanish as they opposed Inca rule. The basic policy of the Spanish towards local populations was that voluntary vassalage would yield safety and coexistence, while continued resistance would result in more deaths and destruction.

Another significant effect on the people in South America was the spread of Christianity. As Pizarro and the Spanish subdued the continent and brought it under their control, they forcefully converted many to Christianity, claiming to have educated them in the ways of the "one true religion." With the depopulation of the local populations along with the capitulation of the Inca Empire, the Spanish missionary work after colonization began was able to continue unimpeded. It took just a generation for the entire continent to be under Christian influence.
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