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So vitamin D is the driving factor: either you lose melanin, or become lactose tolerant, or you die. With dark skin, you can't make enough D from sunlight. If

• trhway 9y ago
  Milk is calcium. Colder climate - bigger body. That needs calcium. Thus milk and vitamin D, both are necessary. Thus pale skin and lactose. Either alone isn't enough.
• TrisMcC 9y ago
  Naturally, milk only contains trace amounts of vitamin D. I don't think ancient humans were fortifying their milk.
  • op00to 9y ago
    Wouldn’t cheese be concentrating the vitamins in milk, sort of fortifying it in as much as it’s making it easier to consume the amounts of milk you need for vitamin d?
• scythe 9y ago
  Milk does not naturally contain vitamin D; fish, mushrooms, and egg yolks are the only natural sources, but the mushrooms have to be exposed to sunlight (which is unlikely; they grow in the shade) and nobody eats that many eggs, so only pescetarian cultures retain darker skin at northern latitudes.
• badosu 9y ago
  The study also points out that there's evidence for sexual selection as well.
• masklinn 9y ago
  > So vitamin D is the driving factor: either you lose melanin, or become lactose tolerant That doesn't make any sense, unless it's reinforced milk contains almost no vitamin D (2 IU per 100g, recommendations are 2500 IU/day for children aged 1~3 to 4000 IU/day for adults). Plus there are lactase persistence clusters outside Europe which make even less sense given the Vitamin D hypothesis (e.g. arabian peninsula, Western Africa). Lactase persistence overlaps much better with historical pastoralism, which makes a lot more sense: milk is high in calories[0], being able to use these calories when they're available is advantageous. Plus it also provides some fat, proteins and B2, B12 and Calcium micro-nutrients in appreciable quantities (15, 20 and 10% DRI respectively for un-fortified whole milk). edit: even more so local, small-scale pastoralism: before refrigeration you'd have had to consume the milk within hours so either a few familial animals or a small herd at the tribal/village level. That could also explain why some cultures have a history of dairy products but not of consuming milk directly (and thus low lactase persistence). [0] cow milk is ~250kJ/100g, and much of that is locked in the ~5g of lactose
• gumby 9y ago
  If you click on the study you'll see that this point is really an artifact of the summary article, not the actual study.
• deviationblue 9y ago
  > Either way, ancient Northern Europeans had to mutate into pale-skinned milk drinkers, because their land is not very sunny. A (perhaps pedantic) correction: it's more accurate to say that mutants who were pale-skinned milk drinkers were more successful at surviving and proliferating in Northern Europe, and so the population gained this mutation. Natural selection is not a driven process, it doesn't have an objective; it is, however, a driving process, where it favors one aspect of a population over another. I think the correct wording is always important when talking about natural selection because these processes are more stochastic then we tend to believe.
  • baddox 9y ago
    This seems like an over-application of the (valid) claim that evolution doesn’t have any specific objective. The sentence you quote doesn’t describe an objective. It only describes a necessity.
• taysic 9y ago
  It is worth noting that some of the people migrating into Europe introducing some of the white skin genes were not from northern regions.