3 ms·

Yes, this is the reason people further from the tropics tend to have lighter skin and are more likely to have genetics allowing for lactose tolerance throughout

by Rury 4y ago

Yes, this is the reason people further from the tropics tend to have lighter skin and are more likely to have genetics allowing for lactose tolerance throughout life. They're natural adaptations by the body, in response to being in an environment which sunlight (and therefore vitamin D) is more scarce.

jjeaff 4y ago
The lactose tolerance part doesn't really make sense because dairy products are not naturally high in vitamin D. Companies add the vitamin D to milk. Butter is an exception because it is nearly all fat, so it has a lot more vitamin D. But, because butter is nearly all fat, it also doesn't contain much lactose and is usually well tolerated by people with lactose intolerance. I have read that the correlation of latitude and lactose tolerance has to do with the fact that milk was less prevalent in warmer climates because it did not store or travel well. So unless you grew up right around milk producing cattle, your gene pool had little exposure too it and thus little evolutionary pressure to continue to tolerate milk after infancy. By contrast, Europe has a much colder climate and was well suited to dairy cows and storing and shipping dairy products.
codethief 4y ago
So you're saying darker skin prevents the body from producing vitamin D? (Not saying it doesn't, I just didn't know.) Also, what does lactose (in-)tolerance have to do with… anything? To my knowledge, the fact that lactose tolerance is that common among Europeans is largely a result of thousands of years of domesticating dairy animals. Not all light-skinned people in the world are automatically lactose-tolerant (or "are more likely to have genetics allowing for lactose tolerance throughout life" as you say). Wikipedia agrees: > Lactase persistence evolved in several populations independently, probably as an adaptation to the domestication of dairy animals around 10,000 years ago. Today the prevalence of lactose tolerance varies widely between regions and ethnic groups. The ability to digest lactose is most common in people of European descent, and to a lesser extent in some parts of the Middle East and Africa. https://en.m.wikipedia.org/wiki/Lactose_intolerance https://en.m.wikipedia.org/wiki/Lactose_intolerance Also see the map on https://en.m.wikipedia.org/wiki/Lactase_persistence https://en.m.wikipedia.org/wiki/Lactase_persistence .
- Mountain_Skies 4y ago
  Seems like skin color is a trade off between protection from skin cancer and getting enough vitamin D. People in areas with abundant sunlight can get all the vitamin D they need from the sun with dark skin while being protected from cancer. People in areas with lower levels of sunlight don't need as much protection from skin cancer caused by the sun but their lighter skin does permit more vitamin D collection from that weaker sunlight.

by Rury 4y ago

jjeaff 4y ago

The lactose tolerance part doesn't really make sense because dairy products are not naturally high in vitamin D. Companies add the vitamin D to milk. Butter is an exception because it is nearly all fat, so it has a lot more vitamin D. But, because butter is nearly all fat, it also doesn't contain much lactose and is usually well tolerated by people with lactose intolerance. I have read that the correlation of latitude and lactose tolerance has to do with the fact that milk was less prevalent in warmer climates because it did not store or travel well. So unless you grew up right around milk producing cattle, your gene pool had little exposure too it and thus little evolutionary pressure to continue to tolerate milk after infancy. By contrast, Europe has a much colder climate and was well suited to dairy cows and storing and shipping dairy products.

codethief 4y ago

So you're saying darker skin prevents the body from producing vitamin D? (Not saying it doesn't, I just didn't know.) Also, what does lactose (in-)tolerance have to do with… anything? To my knowledge, the fact that lactose tolerance is that common among Europeans is largely a result of thousands of years of domesticating dairy animals. Not all light-skinned people in the world are automatically lactose-tolerant (or "are more likely to have genetics allowing for lactose tolerance throughout life" as you say). Wikipedia agrees: > Lactase persistence evolved in several populations independently, probably as an adaptation to the domestication of dairy animals around 10,000 years ago. Today the prevalence of lactose tolerance varies widely between regions and ethnic groups. The ability to digest lactose is most common in people of European descent, and to a lesser extent in some parts of the Middle East and Africa. https://en.m.wikipedia.org/wiki/Lactose_intolerance https://en.m.wikipedia.org/wiki/Lactose_intolerance Also see the map on https://en.m.wikipedia.org/wiki/Lactase_persistence https://en.m.wikipedia.org/wiki/Lactase_persistence .

Mountain_Skies 4y ago
Seems like skin color is a trade off between protection from skin cancer and getting enough vitamin D. People in areas with abundant sunlight can get all the vitamin D they need from the sun with dark skin while being protected from cancer. People in areas with lower levels of sunlight don't need as much protection from skin cancer caused by the sun but their lighter skin does permit more vitamin D collection from that weaker sunlight.