Since I was a little kid I was always skeptical of slathering something all over my body just to go outside. Just thought…how did people survive before this stuff if we really need it so bad.

People didn't used to expose themselves to as much direct sun and covered themselves with a lot more clothes. Traditional clothing in arid sunny areas typically covers everything, look at people in the middle east today.

I live in a very sunny desert area and it's kind of funny when people assume people from here would be "more tanned". We stay in the shade, the sun will kill you! Anyone working outside is wearing wide brimmed hats and typically has all of their skin covered with clothing even in the heat, people typically have their faces covered with cloth as well.

Spending time outside with minimal clothing in direct midday sun is a modern weird behavior.

If you ask „how did people survive“ the answer is more often than not: „with great difficulty“. Take for example simple hygiene measures like using soap or brushing your teeth or disinfecting wounds.

Global migration outpaced evolutionary adaption a long time ago. Many peoples have adapted to local UV conditions, but can now jump on an airplane and are instantly in a completely different environment.

Additionally, if you've ever seen a portrait of a human in the UV spectrum, you'll notice how shiny they look. I'm sure modern people have much less protective oils in their skin as a result of increased bathing required by societal and sanitation norms of modern urbanized habitation.

Many didn't. On top of that, evolution optimizes for reproduction, not long life. With few exceptions, cancer is a disease of the post child rearing aged folks.

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.

White people - depending on your definition, I mean pale-skinned Northern Europeans - are adapted to live north of about 45 degrees.

Obviously they live lots of other places now, but evolution is slow to catch up.

If you drive through France for a day, you can literally see the change from north to south, "could be Dutch" in the far north to "could be Spanish" in the south. Of course lots of people move around but I'm talking about averages.

> skeptical of slathering something all over my body just to go outside

Missing nuance: Outside for how long? And how strong is the sun?

Even with my pasty Northern European complexion, I'm skipping the sunscreen for a 20 minute walk to lunch in November. But for a 10 hour hike above treeline in July? I'll be re-applying every two hours.

Slathering oneself in mud if you need to endure harsh sun exposure is the most common answer I’ve seen to this question. Otherwise, I agree with your comment, the “best practice” of avoiding sun exposure is as unintuitive as the grain-heavy food pyramid.

Often living in a different climate zone, US is well south of Europe.

They survived but for a much shorter time?

I live at a much lower latitude (about the same as Morocco) than my Celtic ancestors did.

Long sleeves and wide brim hats.