In the fifteenth-century Spain of Torquemada, people routinely raised the question about the biological differences between believers and heretics, between Christians and Jews, posited the natural superiority of one group over the other, and invoked the known procedures for coming to terms with the available knowledge. Just before and during the Inquisition, the most important biological argument for the persecution of the Jews centered around the concept limpiezza de sangre or purity of the blood (Lea, 1906). Limpiezza decrees were used to prohibit intermarriage and, quite significantly, required that a candidate for a particular ecclesiastical or secular post prove his Christian ancestry (Coulton, 1938).1