Given natural selection is true, why do we still have genetic eye sight issues? Because I would think bad eye sight would get you killed (or at least the inability to eat) in a hunter gatherer society.
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One answer I have not seen yet is that modern life contributes to our poor eyesight. Focus on things close up all of the time and your eyes struggle to focus at a distance (i.e., you become nearsighted). This is a much bigger issue with computer jobs than it was for our ancestors.
Because humans are communal. They formed tribes and communities, and each person had their job, so it wasn’t necessary for survival for everyone to be perfect. Maybe someone near sighted would be a terrible hunter, but they would be excellent at building fires, cutting meat, making weapons , farming, and weaving clothing, etc.
Alone, the pressure would get you killed, but we hunted in packs, so in MMO parlance, those with the best eyesight could carry the hunting party for scouting and spotting, like Legolas.
Those with bad eyesight might have had better hearing, or endurance, or swimming skill, or a stronger throwing arm or back, and even if you had none of that, somebody had to keep the ladies happy while the hunting party was away. We weren’t always monogamous.
Women tend to have better color differentiation, and men tend to have better motion tracking, which makes sense when you think of traditional hunter/gatherer roles of hunting reserved for men, and gathering reserved for women.
Lastly, we’ve only been living past 40 for the last couple hundred years, so the impact of age-related macular degeneration and astigmatism in post-childbearing years had very little, if any impact on a society’s chance for survival.
It turns out that average eyesight (20/20, meaning you can see clearly at 20 feet what the average person can see clearly at 20 feet) just isn’t as critical an ability as our intuition suggests, that’s all. For most survival-related circumstances, fuzzy vision is perfectly adequate. I can’t think of a single scenario (apart from one purposefully contrived to erase the difference between ‘bad eyes’ and ‘no eyes’) where it would cause an “inability to eat” in any social animal, least of all one with consciousness and the related ability to communicate (in contrast to mere ‘signaling’) which humans have.
The prevalence of nearsightedness has increased exponentially since industrialization and formal education. Excessive near point strain from lots of studying and reading during childhood and adolescence worsens the severity of myopia. Additionally, lack of exposure to UV appears to worsen myopia.
100,000 years ago probably made a difference and then with the bad eyesight would have a harder time and so natural selection would start to breed it out or at least reduce it,
As humans develop with compassion and family units people would be taking care of family members with disabilities unless they became too big of a burden.
Now we have glasses and we think girls with glasses are cute and then we make babies that need glasses. So now it’s probably going in the other direction.
Another example is teeth, people whose teeth went bad early, we’re unbelievably crooked, today we have braces and dentist so there’s no breeding bad teeth out.
If we lived in the jungle and your bad eyesight prevented you from seeing the lion coming up then yeah, total natural selection
You actually answered the question yourself: early humans were a hunter gatherer *society*. If you were a solo hunter and you had bad eyesight, you would probably die and the ones with good eyesight will pass on their genes. But human society developed so that individuals with specific weaknesses, eyesight or other, were compensated for by the strengths of others. Thus, humans with weaker genes are not in a position where they are unlikely to reproduce.
In general, age-related diseases (which are fundamentally genetic in origin, but obviously not the only kind of genetic disease) are not important if they appear after you successfully reproduce. Also, if the typical individuals life span is less than when age-related issues appear, then you don’t have a problem at all (and so no evolutionary pressure) until/unless for some reason life span extends rapidly.
Actually there are less eyesight problems when people grow outside, in the fields and in sunlight, not under artificial light and in semi-darkness a lot of the time.
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