The gowth cycle of eyebrows and eyelashes are a mere blink of the eye compared to head hair. Eyebrows take up to 64 (give or take) days to come back fully. Eyelashes are even more fleeting, taking only four to six weeks to come and go.
The eyebrow is an area of thick, short hairs above the eye that follows the shape of the lower margin of the brow ridges of some mammals. Their main function is to prevent sweat, water, and other debris from falling down into the eye socket, but they are also important to human communication and facial expression. It is common for people to modify their eyebrows by means of hair removal and makeup.
A number of theories have been proposed to explain the function of the eyebrow in humans including that its main function is to prevent moisture, mostly salty sweat and rain, from flowing into the eye, or that clearly visible eyebrows provided safety from predators when early hominid groups started sleeping on the ground.
Recent research, however, suggests that eyebrows in humans developed as a means of communication and that this is their primary function. Humans developed a smooth forehead with visible, hairy eyebrows capable of a wide range of movement which are able to express a wide range of subtle emotions – including recognition and sympathy
Fashion in eyebrow shape has regularly changed throughout the ages and eyebrows have always featured heavily in female fashion, often as part of cultural demands made on women about body hair.
Japanese women and men from the 8th century practiced hikimayu, that is, shaving or plucking the eyebrow hair and painting smudge-like ones higher on the forehead or pencilled in thin ones in a different place. This practice is comparable to that in the Elizabethan era when high status women would remove eyebrows altogether.] Thin eyebrows, achieved by rigorous plucking, were again fashionable in the 1920s and 1930s.