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Comment by zer00eyz | Hacker News Reader

Wow,

I find this funny because through the 50-70's letting kids sleep outside for a nap in the day time was normal in Scandinavian countries.

I remember the 1980's photo of kids getting a solar bath in some Hoth like area of Russia in the winter.

I like this study because it's starting to add "Sensible sun exposure" into the mix. I suspect that we're going to add "physical activity" to that next.

We didn't evolve for 100k years to work at desks for 8 hours a day and hide in houses. Persistance hunting was an outdoor day time activity. Foraging was an out door day time activity. Heading animals was an out door day time activity. Farming was an...

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In college, my Earth science professor claimed that there was no acceptable amount of sun expose since it can give you skin cancer.

I understand the two are correlated, but it made no sense to me. Only in the last few hundred years have humans been able to be indoors nearly 24/7.

Maybe the percentage of skin cancer deaths was acceptable back then? We now try to save every individual no matter what disadvantage they may have been born with thanks to modern medicine and surgery, and that practice has been changing our gene pool.

The genes that predispose you to melanoma are probably the same genes that makes your skin white...

A theory just popped into my head.

For hundreds of thousands of years, we had no soap. We did have water, but swimming and washing in a summer stream isn't hot water, and it's hot water which strips away the oils. And even pre-20th century, people did NOT bath in hot water daily.

Often it was just armpits + groin in a sponge bath.

What if our skin was protected by our own oils? I can imagine that even a small amount of oil, would reduce the amount of UV that gets to the skin.

I know sunblock has minerals(zinc, etc) in it to reflect the sun, but I just googled there are oil based sunscreens too:

"Chemical absorbers: Chemical (or organic, meaning carbon containing) sunscreen ingredients form a thin protective film that absorbs UV radiation before it penetrates the skin."

I can easily imagine that our own oils could provide protection, and block UV but let good frequencies of light through. Yet now we wash a lot of that oil off, with hot showers daily, and shampoo and soap which runs down our body as we shower.

Would be an interesting study.

edit: another thought! The oil on our skin is often policed by bacteria. The bacteria eats that oil, and also any organics (skin flakes, or stuff that sticks to the skin).

That's another level of shield. I imagine that without hot showers, and loads of soap, that layer of oil has bacteria multiple layers deep. And that bacteria moves. A moving, sunshield.. in addition to the oil.

And of course, bacteria exudes waste. That waste is going to have carbon in it, too. So our skin oil would be combination of the oil + living shields + their waste.

I imagine the waste would build up after a while too.

edit2: A harsh response from KennyBlanken, who seems to disagree.

However, this poster quite literally ignores things I stipulated, or gets things mixed up. He then ends with harsh criticism, which seems very un-HN like (eg, personal attacks).

That said:

* Skin oil contains a myriad of ingredients, fatty acids, salt, complex acids, bacteria, their leavings, and more.

All of this is simply ignored by Blanken, who just says "skin oil doesn't block UV, because it doesn't have the same precise ingredients as over-the-shelf sunblock". Further statements about "Google this" are provided, yet clearly I did a bit of quick research, as I provided a quote about sunblock. Again, very un-HN like.

* Weird statements about how long soap has been around for, when all I indicated is that for "hundreds of thousands of years" we had no soap, which is entirely true, and obviously stated in terms of how we evolved. This fact seems to have been missed in the reply, however.

* Discussions about how soap has been around for a while, meanwhile missing the entire point that most humans pre-20th (as I stated) typically just did the sponge bath thing. People didn't shower, and most of humanity did not have running water until the 20th, regardless of rare rich Romans.

None of these rebuttals seem to even consider that the scientific process starts with random thought, eg as I said "A theory just popped into my head.", then consideration, then debunking via actual, real research.

As opposed to some 19th century British-Science-Guild like huffing, including personal attacks and so forth.

KennyBlanken, perhaps you could debate more politely? And follow the guidelines a bit more closely?

https://news.ycombinator.com/newsguidelines.html

Imagine all these small qualities of life that are destroying us without us knowing.

Skin oil does not provide any UV blocking.

The oil in sunscreen is to make it spreadable and dilute the UV-absorbing ingredients, which are things like avobenzone, oxybenzone, and so on.

No offense, but you could have googled "active ingredients in sunscreen."

Further: just because something is called an "oil" doesn't mean it has any similar physical properties compared to another oil.

Recipes for soap date back something like 5,000 years, by the way - and probably were passed down by oral history or demonstration even earlier.

You don't seem qualified to be making (or evaluating) the theories you are coming up with. Not in terms of basic scientific knowledge, critical thinking skills, or research skills.

Your "people didn't wash back then so they had natural sunscreen" is about as well-reasoned as the people who think keto is the best diet because "it's what cavemen ate" (hint: people ate whatever was available to them in their area.)

I mean, anecdotal, but... unhoused people, soldiers, campers, etc sure seem to get plenty tan when outdoors even when not taking regular hot showers.

Anyway, it's good to think outside the box, even if this theory is probably a miss.

True, but white people historically lived in colder climates with (naturally) less sun exposure , which has changed in the last couple centuries.

You have it reversed. The color of your skin determines how much UV protection you get. Skin color is 1-1 correlation to the average hours of daylight a population experiences. High melanin skin is required to live in the equatorial regions to prevent over exposure to UV rays. Low melanin skin is required in the northern regions to prevent under exposure to UV rays.

We saw a mass migration of eastern Europeans to the middle east mid 20th century and the result was the catastrophic increase in skin cancer rates.

We saw a mass migration of middle Easterners to great lakes region in the same period and we saw a catastrophic increase in depression rates.

There are several kinds of skin cancer: carcinomas (which don't usually kill you) and melanona (which does). Carcinomas are indeed positively correlated to sun exposure, but oddly enough melanoma is negatively correlated: sun exposure protects you from melanoma.

Do you have sources I can read on this? I wife has had a couple bouts of melanoma in her mid 20s and her dermatologist tells her to stay of of the sun.

Her dermatologist is right. Take medical advice from MDs, not HN.

My wife is also a melanoma survivor (Stage III) and yeah, the notion that sunlight is negatively correlated with melanoma is utter nonsense.

> but oddly enough melanoma is negatively correlated: sun exposure protects you from melanoma.

I hate to be that guy, but: citation needed.

I did a quick search and the best I could find was speculation that sun might be protective, but the majority of what I found said sun exposure increased your risk of melanoma.

(citation needed) on the melanoma. UV is basically identified as the main cause of melanoma. Unless you meant exposure in low-UV situations. But that's a massive caveat that really needs to be added to that message.

Everything about https://en.wikipedia.org/wiki/Melanoma basically disagrees.

That does not sound correct. Sun exposure is still linked to melanoma risks. Regular sun exposure does increase protection (due to melanin in skin?) but doesn't remove the risks.

Being active in the sun for long period in New Zealand or Australia for example would put you at higher risk for melanoma due to higher UV exposure

Exposure to UV increases your risk of getting cancer, statistically.

Not getting sufficient sunlight - not just for vitamin D production but other things - increases the risk of other health impacts, statistically.

For decades people freaked out about the former, without considering the latter.

I think the research supports what you're saying.

My professor though was essentially saying "stay out of the sun". It was a bit of a charged lecture since his daughter developed skin cancer.

But, my take is sun exposure is perfectly worth the risk. A life without being outside/being in the sun doesn't sound very enjoyable, though of course moderation is important.

Also from Scandinavian countries:

The babies who nap in sub-zero temperatures (https://www.bbc.com/news/magazine-21537988)

"In some studies they found pre-schoolers who spent many hours outside generally - not just for naps - took fewer days off than those who spent most of their time indoors," she says.

Yeah, this is a thing. My wife is Finnish and our first was born in Rovaniemi in early winter. Wasn't terribly cold but we had her on the parvike bundled in a stroller and she slept great.

I'm in Canada and have seen this first hand. snug as a bug in a rug even though it was -10C.

admittedly she was bundled up pretty good in the stroller, and it was near her usual naptime, but was totally asleep by the time we got home from the walk.

I found out the doctors are recommending vitamin D drops for infants. Yet they're loaded with all sorts of junk, like caramel color, polysorbate, etc. Sunlight produces vitamin D, helps break down bilirubin, and produces other beneficial substances. I know which one I'd choose.

Not all of them contain those additives [1] (I believe coconut oil is needed because cholecalciferol is not water soluble), but yes, I agree that they should not be pushed as a substitute for sunlight if you have the choice:

> Each concentrated drop delivers 400IU of vitamin D3, the form naturally found in the body, blended with premium quality fractionated coconut oil. The sugarless formula has no artificial colours, flavours, or preservatives, so it won't interfere with feeding.

[1] https://www.ostelin.com.au/products/infant-vitamin-d3-drops/

Nice! The ones at my pharmacies were filled with junk. This looks great.

There's a big difference between sunbathing in Scandanavia and sunbathing in Florida, though.

+1.

Also a few animals sweat like us. We are indeed not built to sit in one place.

Sweating:depression::sunlight:infection.

I agree.

But you left out one small piece of information:

If you didn't go outside for food you died. If you didn't go outside to till your field you died. If you didn't travel with your animal herd you died.

Then you have Australia here where there's no way sleeping outside during the day would be beneficial due to how harsh our UV rays are, unique to the rest of the world.

I agree, we didn't evolve for 100k years to work at desks for 8 hours and I think so much of that is a bigger problem in of itself, combined with lack of sunlight as just one piece

And the native Australians have the skin pigmentation to deal with it.

I definitely don't (not native, very pale)

I think the parent may be referring to the indigenous Australian (i.e. Aboriginal people) - who are basically black-skinned, and have been here for a lot longer than other races.

(Even they came to Australia from South East Asia originally - tens of thousands of years ago - back when there was a land-bridge).

I know, they were referring to them, I live in Australia.

I was just saying I’m not native and I have pale skin which is worse for sun damage, unlike our indigenous counterparts

Extreme equatorial sunlight still causes skin cancer even in full pigmentation islanders of northern Australia, PNG, Torres Strait, etc.

https://sundoctors.com.au/blog/how-aboriginal-peoples-master...

https://www.ourmobandcancer.gov.au/ways-to-help-protect-agai...

There's some additional protection, even so most people with long Australasian family histories hang out under trees at midday.

  Mad dogs and Englishmen
  go out in the midday sun

EDIT: come to think of it, this may explain the popularity of pith helmets in the chap hop scene: https://www.youtube.com/watch?v=eELH0ivexKA

Hard to believe but I remember australian grandparents claiming you would be a "good mum" if you left infants in the sun. But I also remember being told dark tans were healthy, and people without then looked sick.

In the case of infants, sometimes their ability to break down bilirubin is reduced. small amounts of sun exposure could be recommended

My understanding is when children are born they may get put under a uv light for this. Your grandparents knowledge may be prior to modern treatment

Australia's UV rays are not unique to the rest of the world. There are lots of places in the world where the UV rays are much stronger than in Australia.

"So where on Earth’s surface would we expect the highest UV? Peak UV should occur within the tropics (high sun, low ozone), at a high altitude site, in the Southern Hemisphere. Near the Tropic of Capricorn, overhead Sun occurs during the period when the Earth- Sun separation is a minimum"

Satellite data clearly shows that UV is approximately 1.5x stronger in Peru than Australia, for instance.

> Satellite data clearly shows that UV is approximately 1.5x stronger in Peru than Australia, for instance.

Does this account for the diminished ozone-based UV filtering Australia is subject to?

Yes. Other places, like Peru, also have diminished ozone.

I should have said unlike many places around the world.

My point being in relation to the parent comment was that here you can’t just sleep outside all day. And being outside for extended hours here does irreversible damage without sunscreen very quickly

the first studies that determined the connection between sunlight and skin cancer were based on Australia cabbies.

US cabbies got skin cancer on the left side, because their left arms or sides hung out the window / got more sun. Meanwhile the Aussie cabbies got it on their right side, and at high rates (because anglo-irish in a desert).

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