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Comment by fragsworth | Hacker News Reader

This seems like a bad idea. Our eyes have adapted to living with sunlight for thousands of years.

I have a feeling it will be discovered that there is something wrong with darkening your vision for long periods of time.

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Prolonged exposure to sunlight damages the eyes. Cataracts or damage to the conjunctiva for example. We get much older than a few thousand years ago, and our bodies aren't well adapted to dealing with cumulative sun damage.

Our skin has adapted to living with lions for thousands of years, which is why modern humans are lion-proof.

When I was wearing transitions glasses I noticed I began to feel SADS-like depression during the spring and the fall. It is hard to explain the feeling that I was just not getting enough light. I began to walk around without the glasses on just so I could get more light, but it wasn't enough. When I started to drive without my glasses I knew it was time to try something else. So I switched to contacts and sunglasses. Will never go back.

You mean like sunglasses?

Our eyes have adapted to pure sunlight. But there are scenarios that are fairly new and where our eyes don't work well. E.g. driving on a sunny day, sunglasses can be helpful to see elements both in the (comparably) dark car and the much brighter environment. Your eyes can only adapt to one of those and usually that's the car, leaving you temporarily "blinded" by the road.

The existence of eyes for thousands of years in conjunction with the sun does not imply they have impenetrable defenses from the sun. It just means that they're good enough to allow the animal to survive long enough to procreate.

Thousands of years ago, people didn't generally live much past 30 years old. UV has been proven to have negative effects that show up later in life than that.

Where on earth are you getting this? It was certainly not rare for paleolithic women to see their second and third children live to adulthood.

A paleolithic woman would have had her 3rd kid at around 20 years old tops. Seeing that kid to adulthood is still less than 40 years old. Age-related eye problems don't usually show up until you're over 40.

Oh I thought the proposed expectancy was 30; 40 is more plausible. Also, a third viable child produced by 20 indicates a fairly rosy local situation. Every viable child would have nursed for at least two years. Infant mortality was much higher. Menarche took place later than in modern humans. Famine was more common.

One might think that would simply mean that fertility was lower than I'm proposing, but if you look at what paleolithic humans did that is simply impossible. On foot, they occupied every part of every continent save Antarctica. That required fertility significantly above replacement.

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