For example, different age preferences may be a result of sex differences in mate values assigned to the opposite sex at those ages.A study conducted by David Buss investigated sex differences in mate preferences in 37 cultures with 10,047 participants.The results from the study therefore show that the mean preferred marriage age difference (3.04 years averaging male and female preferred age) corresponds very closely with the actual mean marriage age difference (2.99).
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.
In all 37 cultures it was found that males preferred females younger than themselves and females preferred males older than themselves.
These age preferences were confirmed in marriage records with males marrying females younger than them and vice versa.
Thus, both sexes will have to compete and be selective in mate choices.