The roots racism which I1 call a heresy, began in fifteen-century Spain near the conclusion of the holy wars of the Reconquista. The Christian victories brought large Muslim and Jewish populations under the rule of the Iberian Christian princes. For various reasons, including genuine conversion, threats of violence, social pressure, and a desire to advance in society by adopting the religion of the new overlords, many Muslims and Jews converted to Catholicism. The converted were denoted by former religious adherence, either conversos, former Jews or moriscos, former Muslims. However, Spanish Christian animosity influenced by the legacy of warfare and resentment of the upper-class position as professionals and courtiers occupied by many converted created an obsessive fixation on the truth of their adherence to the Catholic faith. In practice, many “old Christian” Spaniards did not want to treat the converted as fellow Christians, even if the concerned families had been apparent practicing Christians for generations. Known as the Limpieza de sangre, the Spanish judged an individual’s status in the community of the Church based on their ancestry. If an individual had the “wrong” ancestry their public confession of faith was insufficient. This was a heresy, plain and simple, and was opposed by Church authorities at the time. But the heresy persisted as individual and government bias against the converted, eventually becoming part of Spanish law in the sixteenth century and leading to violence and expulsions with many victims. This was the beginning of racism, the belief that one’s ancestry could impede one’s acceptance as a Christian or invalidate requirements that other Christians treat you as a brother or sister in the faith. Simply put you could treat human beings badly based on their descent even if that violated your religious ethics. You could sin against people and their descendant forever, especially the indigenous peoples and the African slaves in the Americas.
(quick notes)
Albert Thompson1
https://www.britannica.com/topic/limpieza-de-sangre
https://www.oxfordbibliographies.com/view/document/obo-9780195399301/obo-9780195399301-0101.xml