sentences:  Studies have shown that owing to their immunological isolation from the peoples of the Old World prior to the first contacts with Europeans from 1492 onwards, some 50-90% of the indigenous population throughout the Americas died from epidemic diseases, exacerbated by the stresses brought on by violent conquest, dispossession and exploitation.This led the Spaniards to supplement aboriginal manpower with slaves from sub-Saharan Africa.Well into the 19th century, mining and agriculture accounted for the bulk of economic activity in the Americas.