Human hair growth
The three stages of hair growth are the anagen, catagen, and telogen phases. Each strand of hair on the human body is at its own stage of development. Once the cycle is complete, it restarts and a new strand of hair begins to form. The rate or speed of hair growth is about 1.25 centimetres or 0.5 inches per month, or about 15 centimetres or 6 inches per year.
Long hair
In most current cultures, it is more typical for women to wear long hair than for men to do so. An American study shows significant correlation between hair length and age, which indicates that younger women tend to have longer hair than older women. A significant correlation was also found between women's hair length and hair quality. Moreover, hair quality was correlated with the women's perceived physical health. Consistent with principles of evolutionary psychology, these results indicate that hair length and quality can act as a cue to a woman's youth and health, signifying reproductive potential. The correlation between the woman's hair length and marital status, or number of children, was however not more than to be expected from the correlation between hair length and age.