Epidemics cut indigenous American population by ~90% in a century

October 20, 2026General

Source: We Were Wrong About America Before Columbus by Michael Button

The scale of it: pre-contact estimates put indigenous population across the Americas above 60 million, with some models suggesting a decline of roughly 90% by the 1600s. Smallpox, measles and influenza hit populations with no prior immunity. Pizarro's 1532 conquest of the Inca met a state already gutted by disease and civil war between the emperor's sons. A 2019 University College London study ties abandonment of farmland to a measurable CO2 dip in Antarctic ice cores around 1610 — rapid reforestation may have nudged the Little Ice Age. 🧊📉

Key facts

Pre-contact estimates put the indigenous population of the Americas above 60 million, with some estimates of a roughly 90% decline by the 1600s
Smallpox, measles and influenza devastated populations with no prior exposure or immunity
Francisco Pizarro's 1532 conquest of the Inca met a state already weakened by epidemics and civil war between the emperor's sons
A 2019 University College London study links the abandonment of cultivated land to a measurable decline in atmospheric CO2 in Antarctic ice cores dating to around 1610
Researchers argue that rapid post-collapse reforestation absorbed CO2 and may have contributed to global cooling or accelerated the Little Ice Age
Chroniclers' population figures were later disputed as either inflated to attract funding or minimised to present the Americas as empty wilderness