Genealogical FictionsMara Elena Martnez's Genealogical Fictions is the first in depth study of the relationship between the Spanish concept of limpieza de sangre (purity of blood) and colonial Mexico's sistema de castas, a hierarchical system of social classification based primarily on ancestry. Specifically, it explains how this notion surfaced amid socio religious tensions in early modern Spain, and was initially used against Jewish and Muslim converts to Christianity.