Eyebrow

Eyebrow
A man's eyebrow and eye
Details
Identifiers
Latin	supercilium
MeSH	Eyebrows
TA	A15.2.07.023 A16.0.00.017
FMA	54237
Anatomical terminology []

The eyebrow is an area of thick, delicate hairs above the eye that follows the shape of the lower margin of the brow ridges of some mammals. Their main function is hypothesized 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 not uncommon for people to modify their eyebrows by means of hair addition, removal and makeup.

It is believed by anthropologists that the main function of the eyebrow is to prevent moisture, mostly salty sweat and rain, from flowing into the eye. Greek physician Herophilos, in his treatise "Anatomy," was among the first to hypothesize such a theory, proposing that the eyebrows are "adorned with hair, so that if copious perspiration came [down], it would be contained by this 'check-point' of hair placed in its way until it is wiped off, so that it could not obstruct the eyes." The typical curved shape of the eyebrow (with a slant on the side) and the direction in which eyebrow hairs are pointed, make sure that moisture has a tendency to flow sideways around the eyes, along the side of the head and along the nose. The slightly protruding brow ridges of modern humans could also be used as a defense structure against the floods of moisture. Desmond Morris, discussing the possible function of the eyebrow in human evolution, criticized this suggestion as non-effective and suggested that the primary function of the eyebrows is to signal the changing moods of their owners. Together with the brow ridges, the eyebrows also shade the eyes from sunlight. Eyebrows also prevent debris such as dandruff and other small objects from falling into the eyes, as well as providing a more sensitive sense for detecting objects being near the eye, like small insects.

Eyebrows also have an important facilitative function in communication, strengthening expressions, such as surprise, anger or sexiness. Many makeup artists view eyebrows as a major feature in defining the face. The eyebrows shape the human face and give definition to one's eyes and forehead. Depending on the shape of the eyebrows, it sometimes can cause what is known as a false facial expression (such as a person's eyebrows shaped to seem as if the person was angry, but really isn't). Some people can also move their eyebrows up and down alternately.