Racism

I suppose this has been percolating in mind for a while. Race is a social construct. Biologically speaking differences between what would be called "races" are minor. If so where does racism as we now it come from? Certainly ethnocentrism, or the belief that one's ethnic or cultural group is centrally important, and that all other groups are measured in relation to one's own, is practically as old as mankind. At what point ethnocentrism became racism is debatable, though many would attribute is to the Reconquista, where Spanish nobles proved their lack of mixing of their blood with their former Muslim and darker-skinned conquers by showing that their skin was pale enough to see their blue veins in, incidentally attributed as being the origin of blue blood as a term for nobility. As time marched on other social and historical factors added to the development of racism. Today, in America at least, the majority of people no longer consider race to be biological factor in determining race. Even so the legacy of racism has persisted.