You detect light to know when to wake up or something is happening. Totally blind people also have the mechanism and why they know when it is morning (unless they are missing the organ). I am sure there are other reasons.
In 2017, over 7 million Americans had vision loss or blindness based on best corrected visual acuity in their better-seeing eye (using autorefraction).
Vision Loss: best corrected visual acuity 20/40 or worse.
Blindness: best corrected visual acuity 20/200 or worse.
Total blindness is the complete lack of light perception and form perception, and is recorded as “NLP,” an abbreviation for “no light perception.”
Few people today are totally without sight. In fact, 85% of all individuals with eye disorders have some remaining sight; approximately 15% are totally blind.
My guess, we evolved in hot areas so would often rest during the hottest part of the day. When you’re napping your brain can probably notice if a shadow blocks the light alerting you to a potential threat.
That’s an interesting thought, but I would suggest it’s the simple answer: the skin around your eyes is already fairly thin compared to areas that experience frictional forces more often such as the soles of your feet or palms of your hands, so your eyelid would also be a similar thickness to your face skin.
I don’t think having thicker eyelids would be much of a disadvantage considering it’s not readily visible so predators wouldn’t know who’s vulnerable like they do when hunting the young or injured, and since humans are social creatures any attack on one would alert the others via sound. Furthermore, how often would a threat cast a shadow over your face before it made itself known in other ways? Probably not enough to give an advantage to one-ply eyelid people to pass on thin genes over thick genes in enough of a way to cause human evolution to run that course.
It’s possible, I just don’t see it being likely. Like most traits, I think it’s just random and has negligible impact on survival/reproduction meaning it doesn’t change.
Eyelids are there to protect and assist with moisture. We have never had a need for eyelids that block out light since we’ve never been active in dark and asleep in light. It’s only very recently have we had artificial lighting that allows breaking/shifting circadian rhythm.
So, if someone wants lots of artificial lighting or decides to be more active at night now instead of daylight, they need to be aware that their eyelids aren’t for blocking out light or the sun and need to ensure their sleeping area accommodates this.
I know this is a joke, but there might be an evolutionary advantage to being able to detect some light and movement when your eyes are closed.
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Chicks blink more than dudes and their eyelids aren’t swoll, so I think I disagree with your premise.
Women’s eyelids are the same as men’s. If anything that just tells you that if you want to become swole you should add more weight, not more reps.
Wait, women also add weight to their eyelids in the form of fake eyelashes and they don’t gain any bulk either. This might be a flawed premise.
They’re clearly not adding enough weight.
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You detect light to know when to wake up or something is happening. Totally blind people also have the mechanism and why they know when it is morning (unless they are missing the organ). I am sure there are other reasons.
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Most blind people have some vision
Complete blindness is pretty rare I think
https://www.cdc.gov/visionhealth/vehss/estimates/vision-loss-prevalence.html
https://www.afb.org/blindness-and-low-vision/eye-conditions/low-vision-and-legal-blindness-terms-and-descriptions
Probably so you wake up when it’s light out
I’m now imagining falling asleep around a campfire, and there’s… a shadow
My guess, we evolved in hot areas so would often rest during the hottest part of the day. When you’re napping your brain can probably notice if a shadow blocks the light alerting you to a potential threat.
That’s totally an uneducated guess though.
That’s an interesting thought, but I would suggest it’s the simple answer: the skin around your eyes is already fairly thin compared to areas that experience frictional forces more often such as the soles of your feet or palms of your hands, so your eyelid would also be a similar thickness to your face skin.
I don’t think having thicker eyelids would be much of a disadvantage considering it’s not readily visible so predators wouldn’t know who’s vulnerable like they do when hunting the young or injured, and since humans are social creatures any attack on one would alert the others via sound. Furthermore, how often would a threat cast a shadow over your face before it made itself known in other ways? Probably not enough to give an advantage to one-ply eyelid people to pass on thin genes over thick genes in enough of a way to cause human evolution to run that course.
It’s possible, I just don’t see it being likely. Like most traits, I think it’s just random and has negligible impact on survival/reproduction meaning it doesn’t change.
I could be wrong though
Eyelids are there to protect and assist with moisture. We have never had a need for eyelids that block out light since we’ve never been active in dark and asleep in light. It’s only very recently have we had artificial lighting that allows breaking/shifting circadian rhythm.
So, if someone wants lots of artificial lighting or decides to be more active at night now instead of daylight, they need to be aware that their eyelids aren’t for blocking out light or the sun and need to ensure their sleeping area accommodates this.
Maybe day/night cycle? I doubt that you will be distinguish anything else from a cloud temporarily blocking the sun.