A recent study suggests that eyelashes have an optimal length and evolved to prevent the eyes from drying out. The eyelashes offer similar protection to that of the eyes, but they do so in a different way. They're almost like the mustaches on your face, Marioneaux said. When something touches them, it activates the flicker response as a defense mechanism.
Without the eyelashes, the flicker response would take longer to activate, because the main trigger would be to see something coming through the eye, Marioneaux said. But this gives him a small warning that there is something nearby that can actually damage the eye, he said. The general findings suggest that there is an optimal length at which eyelashes are perceived as more attractive, which has an adaptive evolutionary basis.