Concept
A beard is the hair that grows on the jaw, chin, upper lip, lower lip, cheeks, and neck of humans and some non-human animals. In humans, usually pubescent or adult males are able to start growing beards, on average at the age of 21. Throughout the course of history, societal attitudes toward male beards have varied widely depending on factors such as prevailing cultural-religious traditions and the current era's fashion trends. Some religions (such as some sects of Islam, and Sikhism) have considered a full beard to be essential and mandate it as part of their observance. Other cultures, even while not officially mandating it, view a beard as central to a man's virility, exemplifying such virtues as wisdom, strength, sexual prowess and high social status. In cultures where facial hair is uncommon (or currently out of fashion), beards may be associated with poor hygiene or an unconventional demeanor. In countries with colder climates, beards help protect the wearer's face from the elements. Beards also provide sun protection. The beard develops during puberty. Beard growth is linked to stimulation of hair follicles in the area by dihydrotestosterone, which continues to affect beard growth after puberty. Dihydrotestosterone also promotes balding. Dihydrotestosterone is produced from testosterone, the levels of which vary with season. Beard growth rate is also genetic. Biologists characterize beards as a secondary sexual characteristic because they are unique to one sex, yet do not play a direct role in reproduction. Charles Darwin first suggested a possible evolutionary explanation of beards in his work The Descent of Man, which hypothesized that the process of sexual selection may have led to beards. Modern biologists have reaffirmed the role of sexual selection in the evolution of beards, concluding that there is evidence that a majority of women find men with beards more attractive than men without beards.
