Why Do We Have Eyebrows?

The old phrase goes that the eyes are the windows to the soul. It stands to reason, then, that the eyebrows and eyelashes are the curtains. Or, as beauty entrepreneur Anastasia Beverly Hills puts it, the brows are the frames. Anastasia herself has a specific, patented ratio that her company uses to ensure they shape a person's brows in the way that best suits their face.

Some might think that kind of eyebrow attention is over the top. But as experts at BBC's Science Focus explain, our eyebrows may have developed at least in part to increase human communication. They describe several expressions, each one conveying a specific and unique emotion through simple shifts in the positioning of the eyebrows.

A 2003 MIT study tested which parts of the face people found most recognizable. Research was conducted by photoshopping images of Richard Nixon and Winona Ryder. One version removed their eyes, while another photo removed their eyebrows. Researchers found that participants could more easily identify people in the photos with their eyebrows rather than their eyes.

In another study published in 2018 in the scientific journal Nature Ecology & Evolution, spatial imaging was used to determine that the brow ridge itself may have developed to allow for more brow movement. Communication is clearly important, but brows may have an even more basic function that is equally as important.

Communication is key, that much is clear. But as Science Focus puts it, the majority of humans — past and present — rely on their sight more than any other sense. It is for this reason that researchers believe we kept our eyebrows even as we evolved and shed most of our body hair. 

Additionally, the eyebrows reduce the amount of water and sweat that drips down into our eyes. Of course there is nothing wrong with sweating. In fact, sweating can be good for you. But salt stings when it gets in your eye and the same can be said for chlorinated or salt water, or even fresh water. More than that, all of these fluids can cause our vision to blur. But thanks to our eyebrows, we can avoid the majority of water that comes down our brows towards our eyes.

Similarly, as LiveScience explains, brows stop dandruff and other debris from falling down our face. It's not something most of us want to think about, but if we get dirt or sand in our hair, there is a chance that it will roll down our foreheads and onto our faces. Our brows direct this debris out and around, shielding our eyes from irritants. So whether they're framing the face or protecting it, there is no doubt that eyebrows are vital facial features.