Eyebrows are mainly to help keep sweat and moisture out of your eyes, which would have been really important back in prehistoric times when humans mainly lived outside and had little shelter. If we didn’t have eyebrows, we probably would have developed really thick eyelashes, to wick away moisture, or else we could have had really protruding foreheads to allow rain or sweat to just fall off!
Awsome question Aleanbh! Through evolution we lost most of the hair on our bodies… so why then did we keep a tiny bit over the eyes? It’s so weird! Well, eyebrows help keep moisture out of our eyes when we sweat or walk around in the rain…. this allows us to see clearly when sweating or in the rain. The arch shape diverts the rain or sweat around to the sides of our face, keeping our eyes pretty dry (not so effective when we get torrential down poor of rain though!). Without that tiny patch of hair on our faces, it would be very difficult to get around in heavy rains or when we’re running around and sweating lots which is probably why we retained (through evolution) these in the first place. Can you imagined trying to run away from some sort of a lion or other predator, but having sweat dripping in your eyes? it not only stings, but you wouldn’t be able to see anything! and surely would be caught. That’s why it was beneficial for this patch of hair (our lovely eyebrows) to remain above our eyes 🙂 Excellent question! well done!