I don't have a horse in the race either way but

> it is good intuition that we survived for thousands of years stark naked without sunscreen and vitamin suplements

That, as an argument, is completely worthless. You don't know how those people lived, how they died, what diseases they had, all you can deduce is that some of them managed to reproduce before keeling over.

And white people that live in California or Florida should note that our complexion evolved in latitudes similar to Canada.

And if you are in the equivalent Southern latitude to Canada (e.g. New Zealand), you still sometimes need sunscreen to avoid the extra UV due to the ozone hole. Perhaps not as bad as it was, but cannot be ignored, although it is variable: https://www.rnz.co.nz/national/programmes/ourchangingworld/a...

The NZ sun is terrible. You feel the sun burning you as soon as you get outside. Burn time can be about 10 minutes on a sunny day, and maybe 20 on a cloudy day in summer.

In NZ we get about 4000 in-situ melanoma diagnosis a year. I was one of them a couple of years ago (at 37).

Wear sunscreen!

Perhaps if we are talking about the South Island of New Zealand and the southern tip of Canada (Toronto). Most of Canada would be closer to the pole.

Yeah, good point. NZ has similar latitudes down here as the USA has up there. Weather is very different since we don’t get continental effects.

Also NZ wasn’t really affected by ozone depletion, but the effects are definitely in our neighbourhood and we were worried. “While the ozone hole does not directly affect ozone concentrations over New Zealand, when it breaks up in spring it can send ‘plumes’ of ozone-depleted air towards us. This briefly decreases column ozone levels by around 5 percent, about the same amount as normal daily variation.”. Also see graph at https://niwa.co.nz/our-services/online-services/uv-ozone and notice ozone is lowest in NZ summer. Also measuring a column of ozone is most relevant in the tropics when the sun can be directly above one at noon, and less relevant when the sun doesn’t get so high above the horizon (location further towards poles, and winter versus summer). https://pubmed.ncbi.nlm.nih.gov/9671831/

For that matter, that complexion also likely evolved with clothes, and people in a sufficiently distant past may have looked quite different. The idea of people looking just like us living without clothes or shelter, presumably like some depiction of Eden, is fanciful.

I am reminded that, in addition to not going about stark naked, mesolithic humans in the British isles were dark skinned.

Also cancer takes a fair while to develop and kill you - well after age of reproduction, at which point evolutions opinion on guiding behaviour becomes much weaker.

> You don't know how those people lived

... without sunscreen.

How do you know they went out during the day and weren't completely or mostly nocturnal?

Within living memory, Americans wore hats pretty much whenever they were outside. If we decide to give up sunblock, we might want to reconsider the change in fashions that got rid of them.

That's a relatively recent phenomenon in human history as well. What about the middle ages? What about the bronze age?

Yeah... let's live like we did in the middle age. Lifetime expectancy was HUGE.

“There is a basic distinction between life expectancy and life span,” says Stanford University historian Walter Scheidel, a leading scholar of ancient Roman demography. “The life span of humans – opposed to life expectancy, which is a statistical construct – hasn’t really changed much at all, as far as I can tell.

Life expectancy is an average. If you have two children, and one dies before their first birthday but the other lives to the age of 70, their average life expectancy is 35.

That’s mathematically correct – and it certainly tells us something about the circumstances in which the children were raised. But it doesn’t give us the full picture. It also becomes especially problematic when looking at eras, or in regions, where there are high levels of infant mortality. Most of human history has been blighted by poor survival rates among children, and that continues in various countries today.”

https://www.bbc.com/future/article/20181002-how-long-did-anc...

Adjust for infant mortality, war, etc., humans are still humans.

You realize hunter-gatherers exist today, right? They go out during the day and are not mostly nocturnal. They're found all over the world.

Because it's obvious to anybody. It's also obvious that modern humans are far less exposed to UV than our ancestors, who pretty much lived like current days hobos spending most of their time on fresh air.

Our human ancestors were not nocturnal. Sleep patterns were probably different, sure, but they went out during the day to gather and hunt for food.

Sunscreen, as we know it, is barely 100 years old (see https://pubmed.ncbi.nlm.nih.gov/33583116/) and we have a lot of information up to that point.

We can also deduce from many sources that humanity did not just "managed to reproduce before keeling over".

I am actually a fan of the sun myself. I feel way better, physically and mentally, when getting decent amounts of sunlight. I would accept some risk in exchange for the benefits. But...

    it is good intuition that we survived for thousands of years 

Humans survived to the age of reproductive viability for many thousands of years.

If your goal is merely to survive until the age at which you can make a baby and rear it there are a lot of risks that can be disregarded. Skin cancer is one. So are all other cancers. No need to worry about long-term dental health either. So many fears and worries melt away. Embrace that hunter-gatherer lifestyle.

Alternatively, if you are hoping to live past your 30s (most of us would like to live at least 2.5x longer!) the lifestyles of ancient civilizations and our hunter-gatherer ancestors may not be your ticket to success.

    stark naked

This is not how people lived.

I don't buy this. Having surviving parents and grandparents confers evolutionary advantage to offspring.

    Having surviving parents and grandparents confers 
    evolutionary advantage to offspring

True but irrelevant. The reality is that lifespans were far shorter back then.

According to this page we had skin cancer for thousands of years: https://www.jaad.org/article/S0190-9622(15)00240-6/fulltext

We also completely changed our way of life. We don't live outside anymore so we have less pigment that protects us from UV.

I don’t know about stark naked - in the northern climes where the fairer complexioned folk roam(ed), furs and wool were a matter of survival.

Anyway, UV sucks, nobody is hurt by minimizing it and supplementing via diet. Hell, in the north the sun doesn’t even rise high enough to be a source of vit D for months on end. You have to get it from diet or not at all.

https://smarttan.com/news/index.php/how-to-safely-effectivel...

Look at pretty much any elder in today's tribal societies, they look like raisins at age 50. Most people would rather maintain some youthful looks which means protecting yourself from the sun.

"we survived for thousands of years stark naked without sunscreen and vitamin suplements"

We also ate differently in the Stone Age, so our vitamin intake might have been different.

Finally, life expectancy in the Stone Age was much shorter. Even excluding infant deaths, few people lived long enough to get cancer. Cancer is a typical disease of old age.

> it is good intuition that we survived for thousands of years

Well, all those people in the past are dead, so no, they did not survive.