Many of those smoke or used to smoke, a lot (continues). I live in a country village in south EU and you can see immediately which of the farmers smoke and which don't. Most of them do, but the ones that don't have smooth skin and look younger than they are, the others look like leather bags indeed and older than they are. I guess you can get the same skin without smoking, I just don't see those here.

It's instructive to look at people who drive for a living. One arm will have significantly more sun exposure than the other and it's trivial to spot the difference as the sun does have a very noticeable aging effect.

I wonder, though, if they got full body sun exposure on a regular basis, if that would change things. It seems unlikely that we would have evolved to have a single part of our body exposed to the sun while the rest wasn’t.

> I wonder, though, if they got full body sun exposure on a regular basis, if that would change things

Yes - their whole body would be subject to the ageing effects of the sun.

> It seems unlikely that we would have evolved to have a single part of our body exposed to the sun while the rest wasn’t

And yet it's common for dark skinned people to have significantly lighter palms and soles of feet as they have less exposure to the sun.

What's interesting is that sun exposure through a car window removes almost all UVB rays and most UVA rays. So it's closer to comparing lower sun exposure vs sun exposure with sunscreen.

Dangerously incorrect, side car windows do not remove most UVA rays.

If I recall correctly, the side windows on cars let through more UVA, while the front windows block both efficiently.

My sister moved to a southern latitude and pretty much immediately aged 20 years. Never smoked.

Smoking or not smoking, things don't go 'immediately', so probably something else going on there.

After a few years she stated looking like a old shriveled hot dog. There's no "something else," it's sun damage, and it looks awful.

Some pictures of truck drivers are also good counter examples. The side with more exposure tend to look older.