They were just stories in the end...

They're a big part of facial recognition. They help keep dripping water out of our eyes (somehow).

They also serve a similar function to eyelashes

They keep sweat out of your eyes. That's why people wear sweatbands on their forehead, they wear them on their wrist so they can wipe the sweat off their eyebrow

Not ok guys :'(

there's actually a tumblr account dedicated to matt smith with eyebrows