Age disparity in sexual relationships

Age disparity in sexual relationships refers to differences in ages of individuals in all sexual relationships. Concepts of these relationships and of the exact definition of a "significant" age disparity have developed over time and vary among societies. Differences in age preferences for mates can stem from evolutionary mating strategies and age preferences in sexual partners may vary cross culturally. There are also alternative social theories for age differences in relationships as well as suggested reasons for 'alternative' age-hypogamous relationships. Age-disparity relationships have been documented for most of recorded history and have been regarded with a wide range of attitudes dependant on sociocultural norms and legal systems.

The evolutionary approach, based on the theories of Charles Darwin attempts to explain age disparity in sexual relationships in terms of natural selection and sexual selection. Within sexual selection Darwin identified a further two mechanisms which are important factors in the evolution of sex differences (sexual dimorphism): intrasexual selection (involve competition with those of the same sex over access to mates) and intersexual choice (discriminative choice of mating partners). An overarching evolutionary theory which can provide an explanation for the above mechanisms and strategies adopted by individuals which leads to age disparity in relationships is called Life History theory which also includes Parental Investment Theory.Life History theory posits that individuals have to divide energy and resources between activities (as energy and resources devoted to one task cannot be used for another task) and this is shaped by natural selection.Parental Investment Theory refers to the value that is placed on a potential mate based on reproductive potential and reproductive investment. The theory predicts that preferred mate choices have evolved to focus on reproductive potential and reproductive investment of members of the opposite sex. This theory predicts both intrasexual selection and intersexual choice due to differences in parental investment; typically there is competition among members of the lower investing sex (generally males) over the parental investment of the higher investing sex (generally females) who will be more selective in their mate choice. However, human males tend to have more parental investment compared to mammal males (although females still tend to have more parental investment). Thus, both sexes will have to compete and be selective in mate choices. These two theories explain why natural and sexual selection acts slightly differently on the two sexes so that they display different preferences. For example, different age preferences may be a result of sex differences in mate values assigned to the opposite sex at those ages.

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