4 ms·

Does anyone know why humans adapted to produce D3 in skin? For mammals, we are one of the most hairless animals. Why is D3 and sun exposure so important for hum

Does anyone know why humans adapted to produce D3 in skin? For mammals, we are one of the most hairless animals. Why is D3 and sun exposure so important for humans? Are there any other animals that have this requirement for health?

cogman10 6y ago
https://www.dsm.com/markets/anh/en_US/Compendium/ruminants/vitamin_D.html https://www.dsm.com/markets/anh/en_US/Compendium/ruminants/v... Looks like other mammals definitely need Vitamin D and produce it in the skin.
- hinkley 6y ago
  So 'we' didn't do it so much as some early mammal started doing it and we all inherited it.
throwaway_pdp09 6y ago
Warning: potential butt-speaking ahead as this is not my subject. I have a suspicion that a lot of these things have a biochemistry that goes back a hell of a long way, and I think there's synthesis of various vitamin D's in fungi. Nearest I can find is https://en.wikipedia.org/wiki/Ergosterol https://en.wikipedia.org/wiki/Ergosterol "Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. Because many fungi and protozoa cannot survive without ergosterol, the enzymes that synthesize it have become important targets for drug discovery. In human nutrition, ergosterol is a provitamin form of vitamin D2; exposure to ultraviolet (UV) light causes a chemical reaction that produces vitamin D2" So nothing to do with humans, and may go back to a common ancestor of fungi and protozoa. Note the particular arrangement of the four carbon rings https://en.wikipedia.org/wiki/File:Ergosterol_structure.svg https://en.wikipedia.org/wiki/File:Ergosterol_structure.svg I believe that's a steroid. You see the same thing in https://en.wikipedia.org/wiki/File:Testosteron.svg https://en.wikipedia.org/wiki/File:Testosteron.svg and much to my surprise the same thing appears in digitalis (the foxglove plant) https://en.wikipedia.org/wiki/File:Digitoxin_structure.svg https://en.wikipedia.org/wiki/File:Digitoxin_structure.svg Which suggests these chemical families go back a very long way indeed and most likely are radiate rather than parallel (edit: I mean convergent) evolution. Anyone who actually knows something about this, please correct or elaborate on anything.
superkuh 6y ago
Birds have a slightly different way of doing it but it still uses sunlight. https://en.wikipedia.org/wiki/Uropygial_gland#Feather_and_body_integrity https://en.wikipedia.org/wiki/Uropygial_gland#Feather_and_bo... > It has also been speculated that in some species, preen oil contains a precursor of vitamin D; this precursor is converted to vitamin D by the action of sunlight and then absorbed through the skin.
amelius 6y ago
Isn't vitamin D a hormone and as such a signaling molecule, which would mean evolution could have picked any other molecule for the signaling?
- mrfusion 6y ago
  That’s always bothered me. Why does our body need a signal to do things it should be doing anyway? And why did it pick something dependent on sunlight to use as a signal?
  - bamboozled 6y ago
    Because we weren’t meant to live in basements, extreme latitudes and dingy old people’s homes so in the face of evolution, it didn’t matter. Why did we decide to leave warmer climates where sun was available ?

cogman10 6y ago

https://www.dsm.com/markets/anh/en_US/Compendium/ruminants/vitamin_D.html https://www.dsm.com/markets/anh/en_US/Compendium/ruminants/v... Looks like other mammals definitely need Vitamin D and produce it in the skin.

hinkley 6y ago
So 'we' didn't do it so much as some early mammal started doing it and we all inherited it.

throwaway_pdp09 6y ago

Warning: potential butt-speaking ahead as this is not my subject. I have a suspicion that a lot of these things have a biochemistry that goes back a hell of a long way, and I think there's synthesis of various vitamin D's in fungi. Nearest I can find is https://en.wikipedia.org/wiki/Ergosterol https://en.wikipedia.org/wiki/Ergosterol "Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. Because many fungi and protozoa cannot survive without ergosterol, the enzymes that synthesize it have become important targets for drug discovery. In human nutrition, ergosterol is a provitamin form of vitamin D2; exposure to ultraviolet (UV) light causes a chemical reaction that produces vitamin D2" So nothing to do with humans, and may go back to a common ancestor of fungi and protozoa. Note the particular arrangement of the four carbon rings https://en.wikipedia.org/wiki/File:Ergosterol_structure.svg https://en.wikipedia.org/wiki/File:Ergosterol_structure.svg I believe that's a steroid. You see the same thing in https://en.wikipedia.org/wiki/File:Testosteron.svg https://en.wikipedia.org/wiki/File:Testosteron.svg and much to my surprise the same thing appears in digitalis (the foxglove plant) https://en.wikipedia.org/wiki/File:Digitoxin_structure.svg https://en.wikipedia.org/wiki/File:Digitoxin_structure.svg Which suggests these chemical families go back a very long way indeed and most likely are radiate rather than parallel (edit: I mean convergent) evolution. Anyone who actually knows something about this, please correct or elaborate on anything.

superkuh 6y ago

Birds have a slightly different way of doing it but it still uses sunlight. https://en.wikipedia.org/wiki/Uropygial_gland#Feather_and_body_integrity https://en.wikipedia.org/wiki/Uropygial_gland#Feather_and_bo... > It has also been speculated that in some species, preen oil contains a precursor of vitamin D; this precursor is converted to vitamin D by the action of sunlight and then absorbed through the skin.

amelius 6y ago

Isn't vitamin D a hormone and as such a signaling molecule, which would mean evolution could have picked any other molecule for the signaling?

mrfusion 6y ago
That’s always bothered me. Why does our body need a signal to do things it should be doing anyway? And why did it pick something dependent on sunlight to use as a signal?
- bamboozled 6y ago
  Because we weren’t meant to live in basements, extreme latitudes and dingy old people’s homes so in the face of evolution, it didn’t matter. Why did we decide to leave warmer climates where sun was available ?