1.) The real function of our eyebrows is the protection of our eyes against moisture – when it rains or when we perspire. The semi-circular shape helps to redirect all the moisture to the sides of our face and keep the eyes dry.
2.) On average, every individual has about 250 hairs in each eyebrow. Research has shown that unplucked eyebrows may have as many as 1100 hairs.
3.) The average lifespan of a hair in the eyebrows is four months – after which the hair falls out and is replaced by a new one.
4.) Eyebrows help communicate emotions, even when we are not aware of it: when the angle of the face changes, so do the eyebrows, and vice versa. Furthermore, when you express your emotions without thinking (for example when scared), you move your eyebrows symmetrically. On the other hand, when you express your emotions intentionally (for example doubt or curiosity), your eyebrows will move asymmetrically.
5.) Eyebrows are essential for recognising faces. Research has shown that people had more problems identifying faces of familiar people when shown their photographs without eyebrows.
6.) By plucking, shaping and drawing eyebrows, we are part of a very long history of facial care. Every culture and period in history had its own method for shaping eyebrows: in Florence during the renaissance, they tended to shave their eyebrows clean off, while American colonial elite during the 18th century liked to emphasise the eyebrows with the fur of grey mice.
7.) Many mammals have eyebrows and use them for expressing emotions. But we are the only species with eyebrows on otherwise hairless skin. This provides us with an evolutionary advantage, since we can thus more easily understand and interpret human facial expressions.