The study found very few instances of older women pursuing much younger men and vice versa.
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).
In August 2010, Michael Dunn of the University of Wales Institute, Cardiff completed and released the results of a study on age disparity in dating.
Dunn concluded that "Not once across all ages and countries ...
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.
Another study also showed a higher divorce rate as the age difference rose for when either the woman was older or the man was older.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.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.In females, relative youth and physical attractiveness (which males valued more compared to females) demonstrated cues for fertility and high reproductive capacity.Buss stated the specific age preference of around 25 years implied that fertility was a stronger ultimate cause of mate preference than reproductive value as data suggested that fertility peaks in females around mid-twenties.Male chimpanzees tend to prefer older females than younger and it is suggested that specific cues of female mate value are very different to humans.Buss attributed the young age preference for females to the cues that youth has.The rational choice model suggests that people look for partners who can provide for them in their life (bread-winners); as men traditionally earn more as they get older, women will therefore prefer older men.One of the concerns of relationships with age disparities in some cultures is a perceived difference between people of different age ranges.