harrydre wrote:Alba wrote:Two reasons why melanin is lost:
1. Creating melanin requires a lot of energy. So if it is no longer needed, the body simply stops producing melanin
2. Too much melanin hinders a person from converting sunlight into Vitamin D. So if you live in a cold area and have too much melanin, you will soon fall sick and die unless you have other sources of Vitamin D. Those with lighter skin tones are better able to process vitamin D from sunlight. So naturally when human beings started to move further north into Europe, those with lighter skin tones were better able to survive. Those with darker skin tones did not survive (natural selection at work). Remember that natural sources of vitamin D like citrus fruits are not native to Europe.
Thats also why Africans who live in Scandinavia are advised by doctors to take Vitamin D supplements.
Explains why people near the tropics are generally more dark skinned.
But you need to remember that you are a product of 2 things
1) Genes
2) Environment
The is why australians (the white kind) are still living in the tropics - they do get a bit darker (Environment) but their shade is still light. there are Africans who have been in the US for years and will never be white.
On genes and "natural selection" - There is also the bit about skin cancers. melanin reduced the chances of skin cancers in the tropics due to over exposure to ultra violet sunlight. The people who migrated up north were from our stock but those who mutated a lighter skin tone survived more because of vitamin D absorption in the high latitude areas of the planet and if someone here mutated and got light skin similar to what the northerners had - chances are they either died off. Again it could have happened and some were seen to be undesirable and females/males refused to have babies with them and progress their gene mutation forward. If it happened that they were alphas as Alba put it - they would force this gene down the line.
Enviromental changes drop off when you die since you don't pass them on. plus the tiny matter of whether they are recessive or dominant for them to "show"
All Mushrooms are edible! Some Mushroom are only edible ONCE!