One example is the size and decorative coloration of feathers seen on many male birds. It is hypothesized that the underlying reason why female birds find a male peacock's tail feathers attractive is their indication of the survival ability of male birds. The feathers would not only be noticeable to females, but also to predators and a hindrance in movement, etc. It would seem easier to survive without this costly display, the females of the species usually possess coloration that blends in well with the features of the habitat. There are many characteristics that both males and females value in a potential mate.
Humans also have gender specific criteria for sexual selection.
On the other hand, men value potential female partners in terms of fecundity, the ability to produce and care for children. Recently, the renowned social psychologist Alice Eagly has criticized the evolutionary explanation for gender specific mate selection criteria. If females were the dominant gender, the favored attributes could be expected to exhibit a reversal in gender assignments. Unfortunately, this proximate explanation cannot be tested since there are no presently known human societies where females socially dominate the males. In other animal species, this reversal in gender assignment for sexual selection criteria does occur.