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How Europeans evolved white skin (2015)

sciencemag.org

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Re: How Europeans evolved white skin (2015)

#51

Post by maxerickson »

forapurpose wrote: post #47
irrational wrote: post #20

Earlier quoted context omitted.

You might want to read some introductory anthropology textbooks. For as long as there have been humans it has been us against them. Them/the others/the strangers/the not us are dangerous and cannot be trusted. There are specific rituals that an other must go through to become a part of the community - the means by which one of the others can become one of us. What separates us from them? It might be skin color, it mi…

> For as long as there have been humans it has been us against them. Them/the others/the strangers/the not us are dangerous and cannot be trusted. It's important to add that the definition of 'other' changes. In the U.S., Protestants and Catholics, Italians and Irish used to riot against each other. 'No Irish Need Apply' was appended to job postings. Jews faced significant discrimination. Sometime around the 1930s, i…

The protestant Anglo-Saxons were the original "white" group. Irish Catholics and such were additions.

(I'm responding to it shifted so that all Protestants became 'white'. which could just be an accidental misphrasing)

Re: How Europeans evolved white skin (2015)

#53

Post by cjensen »

amelius wrote: post #49

Why did we evolve to rely on vitamin D in the first place? It's a hormonal substance, and doesn't carry any energy by itself, so why do we need it so badly?

Short answer it is needed for a few things in all animals, so a source is needed. Most animals can synthesize it.

In evolution, sometimes a mutation will take away the ability to synthesize a vitamin. If the organism gets enough of it from diet, this is not disadvantageous and won't be selected out.

Vitamin D deficiency is present in all primates. So that give you some notion of how long ago the synthesis was lost.

Vitamin C is similar since it is readily available in fresh meat and many plants. It is absent in Haplorhini (the dry-nosed primates).

Re: How Europeans evolved white skin (2015)

#54

Post by telotortium »

quotemstr wrote: post #36
drb91 wrote: post #27

Earlier quoted context omitted.

Just to be clear, the Indo European migration is presumed to be a trade/culture migration—there’s not a lot (any?) evidence that this resulted in much increased genetic transfer. Furthermore, I was under the impression milk consumption generally spread from the middle east with rudimentary cheese production with rennet, reducing the lactase to an easier to digest level. This might have been after the europeans starte…

> Just to be clear, the Indo European migration is presumed to be a trade/culture migration Not the case. You're making the "pots, not people" case, which ancient DNA evidence has thoroughly debunked. Changes in material culture usually do indicate large-scale population movements. Yamnaya remains from the Caucuses, for example, are genetically almost identical to the ones buried in the Corded Ware culture that sprea…

An interview of Ward-Perkins, to get a flavor of his critique: http://www.bu.edu/historic/hs/perkins.pdf

Re: How Europeans evolved white skin (2015)

#55

Post by pessimizer »

zeotroph wrote: post #30
scythe wrote: post #12

Earlier quoted context omitted.

It's not dairy alone that causes height gain. High dietary protein correlates with production of IGF-1 which correlates with bone growth. Casein stimulates IGF-1 production somewhat more than other proteins, but not by much. Indians eat a relatively low-protein diet due to the prevalence of vegetarianism and not actually that much dairy; most of it is fermented, which, IIRC, deactivates casein.

And, as a side note, height correlates with cancer risk "Its results found that for every extra 10cm (4in) of height, when fully grown, the risk of developing cancer increased by 18% in women and 11% in men.": https://www.bbc.com/news/health-34414446 Mechanism unknown, but the mentioned growth factors might be the cause, similar to the increased insulin presence wrt. obesity.

The most convincing explanation for me is that larger people simply have more volume for cancer to start in. If you assume an equal chance for a cancer to start in any cubic centimeter of human body, you'd expect men to be more vulnerable than women to cancer, which is true. You'd also expect height differences to raise the likelihood of cancer with more height and lower it with less, and specifically you'd expect that effect to be stronger (when measured absolutely - "10cm (4in) of height", rather than proportionally to mean volume or mean height) in women, because on average, women are shorter.

You'd also expect fat people to get more cancer, and native American Hispanic or East Asian descended populations in the US to get less than the US average. This is what happens.

Of course there are a million other factors and all cancers are different, but in the general case you can guess the relative cancer occurrence between populations with a guess at the difference in their mean volumes.

This won't keep people from trying to sell you a diet, though. Cancer is terrifying, and the idea that we can control it makes us relax. If you eat very little food, especially in childhood when you need calories to grow, you will get less cancer.

Re: How Europeans evolved white skin (2015)

#56

Post by lordnacho »

defen wrote: post #21

Milk does not naturally contain very much vitamin D, so that's a silly reason to expect lactase persistence to have evolved. A much simpler explanation is that it massively increases the calories available to pastoralist populations. SLC24A5 is an interesting gene - I don't think Vitamin D is the full story. It's an SNP that is alone responsible for 25-40% of skin tone difference between Europeans and West Africans,…

What's the story with East Asians? They have light skin as well, right? Is it the same mutation?

Re: How Europeans evolved white skin (2015)

#57

Post by Gibbon1 »

amelius wrote: post #49

Why did we evolve to rely on vitamin D in the first place? It's a hormonal substance, and doesn't carry any energy by itself, so why do we need it so badly?

I think it's a genetic defect that effects 100% of the population. Inability to synthesize vitamin C is another.

Re: How Europeans evolved white skin (2015)

#59

Post by defen »

lordnacho wrote: post #56
defen wrote: post #21

Milk does not naturally contain very much vitamin D, so that's a silly reason to expect lactase persistence to have evolved. A much simpler explanation is that it massively increases the calories available to pastoralist populations. SLC24A5 is an interesting gene - I don't think Vitamin D is the full story. It's an SNP that is alone responsible for 25-40% of skin tone difference between Europeans and West Africans,…

What's the story with East Asians? They have light skin as well, right? Is it the same mutation?

Completely different set of mutations. So whatever advantage is conferred by SLC24A5 mutation is probably matched by something else in East Asians (possibly EDAR)

Re: How Europeans evolved white skin (2015)

#60

Post by deviationblue »

alejohausner wrote: post #3

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 you can't drink milk, you can't get it from diet. Either way, ancient Northern Europeans had to mutate into pale-skinned milk drinkers, because their land is not very sunny. Cool.

> 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.

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