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Comment by berntb | Hacker News Reader

Uh, light skin, blue eyes and blonde hair is just 6000 year old?! Sounds really weird to get so common so quickly.

This should already be well known, by the mutation speed of the relevant genes?

What about an alternative hypothesis, like sexual evolution?

Edit: From the wikipedia page, this theory seems to be quite recent. Interesting. (Sigh, I liked the idea of blonde neanderthals. :-) )

http://en.wikipedia.org/wiki/Human_skin_color#Evolution_of_s...

"This theory is supported by a study into the SLC24A5 gene which found that the allelle associated with light skin in Europe may have originated as recently as 6,000–10,000 years ago[23] which is in line with the earliest evidence of farming.[47]"

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Peter Frost has been writing about this for years. He comes down on the side of the sexual selection theory, so if you're interested in that, check him out.

http://evoandproud.blogspot.com/2009/07/why-are-europeans-wh...

http://evoandproud.blogspot.com/2010/04/puzzle-of-european-h...

Then how come not every Scandinavian girl have c-cup tits? I thought sexual selection yields wildly variating features. And Scandinavian skin pigment was some time ago strikingly uniform.

But he even contradicts himself in that post. He has an example of a modern experiment where people select brunettes over blondes because of rarity.

So if european whiteness is a product of sexual selection of rare blondes, why didn't it swing the other way when the majority of the population were blonde? In some parts of Sweden and Finland, 85% of the adults are blonde, how could it ever go way above 50%? If the hypothesis was true, then people in those areas would have strongly selected brunettes and reversed it?

Here's what I understand of Frost's opinions:

> if european whiteness is a product of sexual selection of rare blondes

It isn't. European whiteness (of skin) is a product of women being more heavily selected than men, since paleness of skin is a sex characteristic of females. (For example, african boys are born light, and darken over time. African girls are born light, darken until puberty, and then lighten.)

European variation in hair and eye color (but not skin color) is a color polymorphism typical of sexual selection. On this theory, 85% of adults sharing the identical hair color is unexpected.

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Here are some of my own thoughts on your question (I claim no qualification at all to pontificate here):

- What size are these "some parts of Sweden and Finland"? The smaller they are, the less interesting it is that they might appear uniform.

- Do 85% of adults share the identical hair color, or is variation being binned into the category "blonde"? Compare the internal variation of african or chinese hair color.

Sexual selection theories often try to explain large waist big breast as a good competitive advantage for raising kids, a visible fertility trait, and forget that the most populous country has girls with neither...

Sexual selection has always seemed to me to be an answer that begs the question. If you suppose that there's a preference for a trait, that would explain its evolution, but it wouldn't explain how the preference evolved.

I'd assume that evolution happens quite fast if the trait is already there in the population (people are more or less light-skinned everywhere) and there is such a strong selection pressure (much more food available if you can adapt to the lack vitamin D).

Exactly, it's not evolving lighter skin

It's evolving keeping the light skin by neoteny

The canonical example of fast human evolution is lactase (the enzyme for digesting lactose and so cow's milk), thought to have spread widely in <10000 years. http://en.wikipedia.org/wiki/Lactase_persistence#Evolutionar...

There's a theory that some Neanderthals had red hair, via a genetic mutation. That mutation is different to the one causing red hair in Homo Sapiens.

Wikipedia says that the gene mutation for human red hair could be from 20,000 to 100,000 years old.

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