<P> Over the 1st century and a half after Columbus's voyages, the native population of the Americas plummeted by an estimated 80% (from around 50 million in 1492 to eight million in 1650), mostly by outbreaks of Old World diseases . </P> <P> In 1532, Charles V, Holy Roman Emperor sent a vice-king to Mexico, Antonio de Mendoza, in order to prevent Cortes' independentist drives, who definitively returned to Spain in 1540 . Two years later, Charles V signed the New Laws (which replaced the Laws of Burgos of 1512) prohibiting slavery and the repartimientos, but also claiming as his own all the American lands and all of the indigenous people as his own subjects . </P> <P> When in May 1493, the Pope Alexander VI issued the Inter caetera bull granting the new lands to the Kingdom of Spain, he requested in exchange an evangelization of the people . Thus, during Columbus's second voyage, Benedictine friars accompanied him, along with twelve other priests . As slavery was prohibited between Christians, and could only be imposed in non-Christian prisoners of war or on men already sold as slaves, the debate on Christianization was particularly acute during the 16th century . In 1537, the papal bull Sublimis Deus definitively recognized that Native Americans possessed souls, thus prohibiting their enslavement, without putting an end to the debate . Some claimed that a native who had rebelled and then been captured could be enslaved nonetheless . </P> <P> Later, the Valladolid debate between the Dominican priest Bartolomé de Las Casas and another Dominican philosopher Juan Ginés de Sepúlveda was held, with the former arguing that Native Americans were beings doted with souls, as all other human beings, while the latter argued to the contrary and justified their enslavement . </P>

Which two european powers conquered most of central and south america in the 16th and 17th centuries