Historians and anthropologists of the Mediterranean world have, for a long time, assumed that a strictly patriarchal model governed gender relations and that this model was fixed geographically over the entire Mediterranean world and chronologically from the Homeric age to the nineteenth century. More recent research, however, suggests that equality of property rights between men and women was not a progressive trend but a discontinuous series of advance and retreat. By the late Roman empire, for example, women exercised considerable autonomy and independence concerning property rights, even though in theory these were vested in the male head of household. The use of the fideicommissum (a testamentary restriction on alienation of property) during the Roman Empire as a legal instrument to keep the patrimony together was often undermined in practice by the specific exigencies of families that did not conform to the ideal structural model. In more modern examples, even areas with strict rules concerning the ideal transmission of property to the eldest son conformed to the ideal pattern in barely one-third of cases.