Monolids Might Have a Purpose

It just hasn't been proved (or disproved) yet

Hiya!

Partly thanks to my relationship with my sister, human eye shape and color have been a point of peripheral intrigue for most of my life. Our eyes are one of those topics that kinda float in my subconscious accumulating random bits of information it deems as important to remember…. even if I don’t know why.

I’m more interested in eye shape and color than the ocular system. Then again, the more I learn about that, the more fascinated I’m becoming. But, for this newsletter I’m going to talk about eye shape, then I’ll talk about our eye colors in Curious Life on Monday.

A bit of back story

I’m not sure if I’ve mentioned this before, but my sister is Chinese. She came home to our family two days before my ninth birthday, when she was four and a half years old. Thankfully, we’ve had an unbreakable bond ever since even though we’re incredibly different—and I’m not just talking about our looks.

Though, of course, appearance comes up too—especially during our teen years when self-comparison is an obsessive compulsion. My sister was not only a minority in school but also in her own family. She often confided her insecurities about the shape of her eyes. We spent hours talking about beauty standards and reminding her that she’s drop-dead gorgeous exactly as she is.

We laughed together at how she thought I was prettier than her, but I thought she was prettier than me. I have blonde hair, green eyes, an average build, and pale skin. She’s blessed with long silky black hair, almond eyes as dark as an abyss, sun-kissed skin, and a petite frame that’s strong as stone. We’re like the sunrise and Christmas lights, both beautiful in their own way.

Anyway, the point is, the differences in our eye shape intrigued me. Then several years ago I watched a documentary that mentioned an evolutionary reason for the almond shape of some Asian people’s eyes. Today, I decided to see if what I remember is true.

Is There an Evolutionary Purpose for Monolids?

My sister has what’s known as monolids, which basically means she doesn’t have a crease in her upper eyelid. This trait appears in about half of the Asian population, mostly those of East and Southeast Asian, Polynesian, or Native American descent.

But what I want to know is, is there an evolutionary purpose for monolids?

I can’t remember the name of the documentary I watched, but it had something to do with tracking prehistoric human migration. Over a thousand volunteers submitted their DNA for the study, and researchers used it to track the path each person’s ancestors likely took out of Africa. They had everyone who participated gather in a park and grouped people together based on migration routes. It was a whole thing.

At one point, they mentioned that some of the differences in our appearance can be traced back to our ancestors’ migration patterns. Those who traveled toward or through regions like the Himalayas evolved monolids to see better in snowy and windy conditions. But is it true? Maybe.

It’s Still A Theory

As far as I can tell, no one has either proved or disproved the theory that monolids formed as an evolutionary advantage. Though, it seems to make sense given a couple of factors.

I mean, when anyone is in snowy and/or windy conditions, the first thing we instinctually do is squint. We do this to protect our eyes from debris flying in the wind, but squinting also helps us see better and reduces glare which can be blinding with snow.

Image source: Canada’s History

This basic human instinct is reflected in the design of ancient snow goggles to protect the human eye from snow-blindness— a type of sunburn for the eyes that can take a couple of days to heal. The snow goggles have a thin narrow slit that looks almost too thin to see out of, yet they’ve protected eyes dating back to the prehistoric Inuits.

Perspective Shift

It’s a solid theory that monolids evolved to protect the eyes during snow and wind, but we may never know for sure. Still, it’s amazing the different traits we develop throughout time. Every single one of us is a homo sapiens, and yet our appearances vary. We have different skin colors, hair colors, and eye colors. We come in all shapes and sizes. Yet each one is beautiful.

Our diversity is more than that though, our traits were and still are needed to survive. Every attribute of us has been finely tuned to serve us in the best way possible. We rarely think about the hundreds of thousands of years it took to mold and shape us with all kinds of features and benefits which allow us to thrive during life. In a way, our bodies tell the story of our ancestors.

Photo by isco on Unsplash