In colonial Spanish America, civil rights and responsibilities were based directly on the degree of European blood that a person had. Racial classifications were highly elaborated, and minor distinctions in ancestry were carefully recorded. While these terms have highly precise definitions, in actual practice they were often used based on impressions of skin color rather than definite knowledge of ancestry. In addition, when racial distinctions were made, they may have been determined by the individuals present or arbitrarily by a priest or official recording the information. The connection of the Castas system in colonial New Mexico will be explored. The instructor will show how DNA studies compare to the Spanish Castas system and the ramifications on modern identity. He will also discuss which New Mexico families reflect the Castas system through DNA analysis.