Gilles Saint-Paul (2008) argued that, based on mathematical models, human female hypergamy occurs because women have greater lost mating opportunity costs from monogamous mating (given their slower reproductive rate and limited window of fertility), and thus must be compensated for this cost of marriage. Marriage reduces the overall genetic quality of her offspring by precluding the possibility of impregnation by a genetically higher quality male, albeit without his parental investment. However, this reduction may be compensated by greater levels of parental investment by her genetically lower quality husband.