Similarly, a preference for such a trait by the opposite sex will also be selected for. These two processes work in tandem, so that both the trait itself and a preference for it co-evolve. Parental investment theory says that the sex that invests more in their offspring will be more selective in choice of mates. Symons also argued that adaptive mechanisms are represented in an organism's psychology, not just its behavior, because behavior may be constrained by a number of other factors. Main Ideas Behind Sexual Selection Theory Buss talks about the Sexual Strategies Theory, which focuses on desire.
Desire is at the foundation of sexuality and mating.
The desires of one sex determine which tactics of attraction should be used by the opposite sex. The fulfillment of desires within a relationship helps fulfill effective mate retention tactics. Effective mate retention then can produce harmony between the sexes. Men and women both have short and long term strategies in their choosing who to mate with. Preferences shift according to what strategy they are trying to pursue.