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.