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".