Probably you would never have guessed why you have the pink circle in your eye, and the answer will surprise you! For some this is a defect.
The answer is very easy, and it is hide in the evolution. Pink corner of your eye is caused by point in our evolutionary development when we have inner eyelids like birds and reptiles.
The tiny crescent-shaped area within the pink corner of the eye known as the plica semilunaris has been the subject of much discussion and debate, especially amongst evolutionists and creationists.
Evolutionists say that the presence of this pink crescent in the corner of our eyes is proof that we evolved from creatures that once had a functional nictitating membrane. Their argument is that we have retained this now-pretty-much-useless vestigial organ because it hasn’t yet been selected against by evolution.
Some creationists say that the plica semilunaris is not proof of evolution because it functions to make and collect “sleep” that we get in our eyes in the morning. Sleep is secreted from a combination of sources including the lacrimal gland, conjunctival goblet cells, the meibomian gland, in some cases also from nasal mucous overflow, and perhaps a little from the nearby lacriminal caruncle. The plica semilunaris may contribute to the secretions because it is rich in goblet cells which make mucus.
So why do we have the pink corner of the eye? Well, both the lacrimal caruncle and the plica semilunaris contain cells which allow it to secrete things which may contribute to our tears and their functions in protecting our eyes, keeping them moist and healthy, but could the plica semilunaris be a remnant of a third eyelid? If it is, what a shame that we didn’t retain it!
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