As humans evolved, our species lost most of the thick hair that covered our bodies, leaving patches here and there. One of the survivors, curiously, were the eyebrows.
Scientists think that there are several reasons why humans have eyebrows. One of the most important is to help keep moisture and debris out of our eyes. Eyebrow hairs grow outward toward the sides of the face, and that helps wick moisture away from the eyes. Eyebrows are also crucial for facial expressions and communicating subtle emotions. For example, a raised eyebrow can express skepticism or interest, and two raised eyebrows can communicate surprise.
In 2015, scientists found a significant link between specific genes and eyebrow appearance. Four genes affect eyebrow texture, one gene determines eyebrow shape, and five genes affect eyebrow hair color.
Some eyebrow-raising facts:
- Some medical conditions such as alopecia can cause eyebrow hair to fall out. An underactive thyroid can cause eyebrows to thin, and lupus may also make that hair fall out.
- Years of waxing or tweezing eyebrows can permanently affect their softly arching shape. Injuries to the skin near your eyebrows can also impede hair growth or alter eyebrow shape.
- Eyebrows may turn gray before or after the hair on a person's head. This may be because they have a different texture and structure than the hair on the head.