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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 co

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.

selcuka 3y ago
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.
- klipt 3y ago
  The genes that predispose you to melanoma are probably the same genes that makes your skin white...
  - b112 3y ago
    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 https://news.ycombinator.com/newsguidelines.html
    - seoulmetro 3y ago
      Imagine all these small qualities of life that are destroying us without us knowing.
    - KennyBlanken 3y ago
      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.)
    - JohnBooty 3y ago
      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.
  - selcuka 3y ago
    True, but white people historically lived in colder climates with (naturally) less sun exposure , which has changed in the last couple centuries.
  - quandrum 3y ago
    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.
alejohausner 3y ago
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.
- chasebank 3y ago
  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.
  - borski 3y ago
    Her dermatologist is right. Take medical advice from MDs, not HN.
  - karmajunkie 3y ago
    My wife is also a melanoma survivor (Stage III) and yeah, the notion that sunlight is negatively correlated with melanoma is utter nonsense.
- bsuvc 3y ago
  > 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.
- viraptor 3y ago
  (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 https://en.wikipedia.org/wiki/Melanoma basically disagrees.
- thevagrant 3y ago
  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
KennyBlanken 3y ago
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.
- shepherdjerred 3y ago
  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.

selcuka 3y ago

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.

klipt 3y ago
The genes that predispose you to melanoma are probably the same genes that makes your skin white...
- b112 3y ago
  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 https://news.ycombinator.com/newsguidelines.html
  - seoulmetro 3y ago
    Imagine all these small qualities of life that are destroying us without us knowing.
  - KennyBlanken 3y ago
    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.)
  - JohnBooty 3y ago
    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.
- selcuka 3y ago
  True, but white people historically lived in colder climates with (naturally) less sun exposure , which has changed in the last couple centuries.
- quandrum 3y ago
  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.

alejohausner 3y ago

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.

chasebank 3y ago
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.
- borski 3y ago
  Her dermatologist is right. Take medical advice from MDs, not HN.
- karmajunkie 3y ago
  My wife is also a melanoma survivor (Stage III) and yeah, the notion that sunlight is negatively correlated with melanoma is utter nonsense.
bsuvc 3y ago
> 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.
viraptor 3y ago
(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 https://en.wikipedia.org/wiki/Melanoma basically disagrees.
thevagrant 3y ago
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

KennyBlanken 3y ago

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.

shepherdjerred 3y ago
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.