Curious Kids: why are our top eyelashes longer than our bottom eyelashes?

Research output: Contribution to journalOnline ResourceEducation

Abstract

[Extract]
The upper eyelid is larger, longer and has deeper roots so it can support more luscious lashes.
All mammals have this feature, but why have the eyes developed this way?

The most significant reason is to protect our eyeballs. But having longer top eyelashes can also help us express our feelings and communicate with others.

They protect you
We have between 90 and 160 eyelashes in each upper lid, each of which grow between 8mm and 12mm long. In each lower lid, we have around 75 lashes which grow 6–9mm long.

Together, your long top and shorter bottom lashes provide a curtain of protection that covers the whole eye socket. This stops dust, insects or sweat getting into your eye and hurting it.

Without eyelashes, your eye would also dry out much quicker, and would be more likely to catch nasty germs. This is why people without eyelashes have to blink much more often.
There is actually an “ideal length” for upper eyelashes.

Using eyelash lengths from humans, as well as across a range of animal species, this is one-third the width of the eye. Any shorter and wind gets through too easily. Any longer and the wind starts to become caught under the lashes, with both scenarios causing the eyes to dry out more.
Original languageEnglish
JournalThe Conversation
Publication statusPublished - 25 Jun 2020

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