Here we present a theory on the origin of allopatric primate species that follows - at least in Neotropical primates - the irreversible trend to albinotic skin and coat color, called "metachromic bleaching." It explains why primates constitute such an exceptionally diverse, species-rich, and colorful Order in the Class Mammalia. The theory is in tune with the principle of evolutionary change in tegumentary colors called "metachromism," a hypothesis propounded by the late Philip Hershkovitz. Metachromism holds the evolutionary change in hair, skin, and eye melanins following an orderly and...