Eyebrows' importance

The presence of eyebrows is more important for facial recognition than the presence of eyes. Eyebrows may serve as high-contrast lines that give the appearance of the brow greater clarity and emphasis, and their associated musculature allows for sophisticated, often involuntary gestures that may be discerned from a relatively large distance. As such, the eyebrows appear to play an important role in the expression of emotions and in the production of other social signals, and they may also contribute to the sexual dimorphism.