Beard
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.[1]
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.[2] 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.[3]
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.[4]
Biologists characterize beards as a secondary sexual characteristic because they are unique to one sex,[citation needed] 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.[5] 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.[6][7][8]
Evolutionary psychology explanations for the existence of beards include signalling sexual maturity and signalling dominance by the increasing perceived size of jaws; clean-shaved faces are rated less dominant than bearded.[9] Some scholars assert that it is not yet established whether the sexual selection leading to beards is rooted in attractiveness (inter-sexual selection) or dominance (intra-sexual selection).[10] A beard can be explained as an indicator of a male's overall condition.[11] The rate of facial hairiness appears to influence male attractiveness.[12][13] The presence of a beard makes the male vulnerable in hand-to-hand fights (it provides an easy way to grab and hold the opponent's head), which is costly, so biologists have speculated that there must be other evolutionary benefits that outweigh that drawback.[14] Excess testosterone evidenced by the beard may indicate mild immunosuppression, which may support spermatogenesis.[15][16]
Beard hair is most commonly removed by shaving or by trimming with the use of a beard trimmer. If only the area above the upper lip is left unshaven, the resulting facial hairstyle is known as a mustache; if hair is left only on the chin, the style is a goatee.
