I don't buy that as an argument. It's the same argument used to push all kind of hoaxes or fad stuff. We live longer than what we used to do, so not everything we did in the stone ages can have been beneficial.

Average lifespan has increased, meaning more people survive early deaths due to disease and injury that we can now prevent, but as individuals we haven't broken through any maximum age barriers.

That said, sun bathing is a modern phenomenon. Our ancestors knew enough to assess that painful sunburns were bad and mitigated their exposure by wearing large hats and clothing with long sleeves. I'm sure even primitive peoples would cover themselves when necessary. If you spend a lot of time working outside you also develop a very dark tan which helps quite a bit. Modern people seem to suffer mostly from spending so much time indoors that even moderate sun exposure on the weekend produces a damaging sunburn.

People are generally taught things like this through mildly hysterical news broadcasts from moralizing non-specialists. This is why it's surprising for people. They've been taught the sun is scary.

If you don't put sunscreen on your kids, it's tantamount to abuse. (I recently experienced this walking through the woods at 10 AM with a family member, no I don't need any sunscreen for a short hike through the trees)

Men are known to be callous dare-devils sometimes, but Women also exhibit a curious lack of good risk assessment that fits this pattern.

They either over-cautiously drink 8 bottles of water a day for dubious health benefits, or they uncaringly approach some wild animal that they cannot imagine goring to death them a few seconds later.

People evolved to live in a fairly small area of the world rather than flying to distant places with different amounts of sunshine than our ancestors likely dealt with in the areas where they spent generations.