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 ...
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.
A study conducted by David Buss investigated sex differences in mate preferences in 37 cultures with 10,047 participants.
In all 37 cultures it was found that males preferred females younger than themselves and females preferred males older than themselves.
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.
A 2003 AARP study reported that 34% of women over 39 years old were dating younger men.
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 social theories for age differences in relationships as well as suggested reasons for 'alternative' age-hypogamous relationships.
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.