Alejandra Aristizabal / Fusion

Watch any mascara commercial, and you’ll likely find yourself mulling: Why can’t my eyelashes be longer? Well, actually, according to science, your lashes are the perfect length.

In at least 22 species of mammals including humans, eyelash length is one-third the width of the eye—the ideal length for controlling airflow and hydration and keeping dust and other tiny junk out of the eye, according to researchers from the Georgia Institute of Technology.

Alejandra Aristizabal/Fusion

Led by David Hu, an associate professor of mechanical engineering and biology—who has also studied the time it takes for mammals to empty their bladders and the frequency at which wet dogs shake—the team examined mammals ranging from giraffes to snow leopards to armadillos. In all species studied, they found that the length of the eyelash was about one third the width of the eye.

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The researchers also designed and built an artificial eye and a small wind tunnel, meant to mimic airflow around the eye, and found that lashes one-third of the width of the eye most effectively diverted dust and other particles.

So if you’re a false lash wearer and have been wondering why your eyes have been a little dry, there you go. Also, sorry about your dry eyes.