Why do humans have eyebrows?

Eyebrows are an often overlooked feature of the face. Without much fanfare they automatically do their job of protecting the eyes from the glare of the sun and from small hazards like dust, dirt, sweat, and rain. Eyebrows act as a barrier, diverting moisture away from the eyes toward the sides of the face through their shape and the direction of their hairs and capturing small particles before they reach the eye. Moreover, eyebrows can shield the eyes from the glare of the sun by pulling forward toward the bridge of the nose, making a projecting “roof.”

Beyond their protective function, eyebrows are also great for nonverbal communication. They help convey a wide range of emotions, from surprise to anger, and everything in between. By raising, lowering, or furrowing our eyebrows, we can express complex feelings without uttering a single word. A few scientists have argued that as human relationships became increasingly complex, the brows of archaic hominins evolved to become the more mobile eyebrows of modern humans in order for eyebrows to demonstrate subtle emotions. The ability to express emotions and intentions through facial expressions, including eyebrow movements, may have been advantageous in building social bonds and avoiding conflicts. In a way, eyebrows are like the original emoji, helping us communicate long before the advent of smartphones.