 Scientists also view the ability to grow very long hair as a result of sexual selection , since long and healthy hair is a sign of fertility and youth . An evolutionary biology explanation for this attraction is that hair length and quality can act as a cue to youth and health , signifying a woman 's reproductive potential . As hair grows slowly , long hair may reveal 2 – 3 years of a person 's health status , nutrition , age and reproductive fitness . Malnutrition and deficiencies in minerals and vitamins due to starvation causes loss of hair or changes in hair color ( e.g. dark hair turning reddish ) . 
