First Published in 2004. This text argues that there is nothing obvious or natural about our ideas of sex and race and looks at the evolution of these ideas. The author contends that the slow crystallization of ideas on human races over the last few centuries can be grasped through the study of signs and their systems. However, race and sex are in no way purely abstract or symbolic phenomena. They are the hard facts of society. To be a man or woman, black or white are matters of social reality. To be a member of a particular race or sex does not bring with it the same opportunities, the same rights or the same constraints. The author examines how these constraints operate and shape our life experience. From a more theoretical standpoint, the text tackles the particular links between the daily materiality of social relationships and mental conventions. Materiality and ideology (in the sense of the perception of things) are two sides of the same coin. Relationships of sex and race follow an ancient history of physical right of the one over the other. Slavery and patriarchy are defined by direct physical rights which is not without its consequences.