Differences in age preferences for mates can stem from evolutionary mating strategies and age preferences in sexual partners may vary cross culturally.
One of the concerns of relationships with age disparities in some cultures is a perceived difference between people of different age ranges.
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.
Age disparity in sexual relationships is the difference in ages of individuals in sexual relationships.
Concepts of these relationships, including what defines an age disparity, have developed over time and vary among societies.