In evolutionary psychology, youthfulness (also called youngness) is one of a number of traits, including averageness and symmetry, associated with health, physical attractiveness, and beauty in a human being. Youthfulness is characterized by vigor, flexibility, bounciness, smooth body surfaces, and babyfaceness,
Youthfulness may be a universal source of attraction across cultures because it is associated with fertility. Men and women have different fertility curves. Men, for example, are often capable of reproduction in their 70s, whereas women show difficulties and complications after age 45. Outward physical appearance tends to exemplify inner fertility levels, and the age of maximum fecundity for the female (i.e. the age at which she is most likely to be successful at bringing her fetus to term) is age 22. Thus youthfulness is traditionally valued more in females than in males.
In terms of mate desirabilities, aside from such common wants such as sincerity and faithfulness, "youthfulness" tops the list for men, whereas with women, "economic capacity" is the highest rated.