The ozone layer wasn't as weak as it is now. We receive more radiation from the sun at the surface than we did before CFCs.

In the past, people, in general, remained in the general vicinity of where they were born. Different skin types adapted to different amounts of sunlight.

We also didn't have the knowledge to link death and disease with their actual causes.

That said, in the past, people used variety of materials for sunscreen without the knowledge that "too much radiation bad". Mud/clay/etc seems to be something multiple cultures over time used. In cultures where working in the sun is common, wearing long clothes that blocks the sun is also a thing, and works like sunscreen.

Given that last point, I think baking in the sun while nearly naked to the point of developing disease is a relatively recent cultural thing, but that's just a guess.