He studied the effect and concluded that the stimulus for increased beard growth was related to the resumption of sexual activity.Despite DHT's relationship with terminal body and facial hair growth, the dominant hormone in facial hair development is likely the male sex hormone testosterone, with DHT more closely associated with beard growth speed rather than density (or "coverage"); moreover, neither hormone acts alone, depending instead on the quantity of androgen receptors on the face.
Various hormones stimulate hair follicles from different areas.
DHT, for example, may also promote short-term pogonotrophy (i.e., the growing of facial hair).
The hairs of a bushy beard will have a relatively long anagen phase.
The hairs of some men have shorter anagen phases and consequently have sparser shorter beards.
A beard is the collection of hair that grows on the chin and cheeks of humans and some non-human animals.
In humans, usually only pubescent or adult males are able to grow beards.
Modern biologists have reaffirmed the role of sexual selection in the evolution of beards, concluding that there is evidence that a majority of females find men with beards more attractive than men without beards.
Evolutionary psychology explanations for the existence of beards include signalling sexual maturity and signalling dominance by increasing perceived size of jaws, and clean-shaved faces are rated less dominant than bearded.
From an evolutionary viewpoint the beard is a part of the broader category of androgenic hair.
It is a vestigial trait from a time when humans had hair on their face and entire body like the hair on gorillas.
The evolutionary loss of hair is pronounced in some populations such as indigenous Americans and some east Asian populations, who have less facial hair, whereas people of European or South Asian ancestry and the Ainu have more facial hair.