Why are there so many blue eyed people?

[Heraclitus]

No. POLYGENIC TRAITS.

A kid is born with somewhat lighter skin than average. He still has brown eyes. Maybe a bit lighter. He absorbs sunlight better. He has a better chance of avoiding rickets, cognitive disorders etc. Him and others like him reproduce better. As time goes on, more and more of the light-skinned/blue-eyed genes get turned on in more and more of the population through continuing mutations and natural selection. Eventually blue eyed kids start showing up instead of just light brown eyed kids. The process continues. Pretty soon it's hard to find brown eyes anywhere.

Ok, makes sense. Missed when you first mentioned it. Thanks.



But please admit that using the Jews was a bad example.

[KrazyHorse]

cultural identity/language =/= genetic diversity

Who the **** said it was?

Also "whomever he choose"? Are you saying genetic mixing is somehow not happening if I don't marry a well to do instead of a low class woman?

WTF Waltzing? How about living in a city for a decade?

Are you being deliberately dense?

Perhaps this is a cultural thing, NA probably has higher mobility for a longer time than European countries. Maybe that is why an effect that has barley taken off in my country seems to be "the last 50 years" in Canada. And I due to inertia see the change of post WW2 as significant but not so much as to eclipse previous movement in the first half of the 20th century, the 19th century and what came before.

Perhaps you don't realize this, but EVEN IN NA geographic mobility is hugely higher now than it was 50 years ago. And the impairments to marrying outside your own ethnicity or EVEN YOUR OWN HOME TOWN are far lower today than they were previously. A century ago Italians and Irish were barely considered "white". And they hated each other too. 35 years ago my father (English speaker) married my mother (French speaking family, but educated in English). They were both heartily discouraged by their respective families. They grew up 10 km from each other. My mother's mother, who was half-Scottish, half-French told my mother that the Irish "didn't bathe regularly". I don't think you realize how ghettoized society was. The rate of genetic mixing is literally multiple orders of magnitude faster today than it was even 2 centuries ago.

[KrazyHorse]

But please admit that using the Jews was a bad example.

Not at all. You say that there were cultural divides between them and the majority populations where they lived. Of course. Just as there was a cultural divide between a Northern Englishman and a Southerner. They barely spoke the same language, by the way (until a couple of centuries ago, and excepting the upper class). And even more so between an Italian and a German etc

[KrazyHorse]

BTW, I can still trace my ancestry back to "pure" ethnic strains. And I'm a ****ing mutt (even more so than most).

I'm Scottish, French, Irish and Iroquois. And none of those mixings happened more than 4 generations ago. Despite the fact that the French side has been in NA for 400 years and the Scottish and Irish for 125 or so.

[Kuciwalker]

Hera, are you deliberately being obtuse?

A same-color eye preference among males would NOT lead to a spread of a small mutation. It would merely make the mutation self reinforcing among a small population.

However that could easily result in blue eyes becoming highly correlated with genes or quasi-inherited traits that do provide a competitive advantage (e.g. being from Europe).

[Dr Strangelove]

According to the Romans the Germans were primarily a brown haired, brown eyed people. The Scythians however were described as golden haired, so the genes for blond hair and blue eyes may actually come from Russia. When the Huns came storming across the Eurasian land mass they drove native peoples before them, so perhaps the Scythians introduced the genes for blond hair and blue eyes into central and northern europe at that time.

Let's say you're a conquering barbarian from the east. Your troops have already raped and slaughtered the male villagers, the elderly and the children, and now you have to choose some of the women to take with you. Which are you going to take, the plain-jane dime-a-dozen brown haired brown eyed chicks or the boojim with eyes the color of the sky and hair the color of golden booty? Sure you could be practical and take the plain chick. She's sturdy, hard working and will probably give you good mileage, but the snazzy sports model makes your loins quiver. Tell you what, take the blonde as your wife and the brunette as your slave. Make the brunette carry the blonde so she'll be good and rested for the night times.

[KrazyHorse]

However that could easily result in blue eyes becoming highly correlated with genes

a) Blue eyes are already highly correlated with genes, being as they are an inherited trait.
b) If you mean that it would increase the prevalence of the phenotype relative to teh prevalence of the genotype, then yes. That's what I said. But that's not really the "mystery" here.

or quasi-inherited traits that do provide a competitive advantage (e.g. being from Europe).

Don't understand what you mean here.

[Kuciwalker]

However that could easily result in blue eyes becoming highly correlated with genes

a) Blue eyes are already highly correlated with genes, being as they are an inherited trait.

Smartass fail "genes that provide a competitive advantage" i.e. genes contributing to traits other than eye color*.

* this is given the hypothesis (raised earlier) that blue eyes don't provide a competitive advantage, or don't provide enough of one to explain their prevalence.

b) If you mean that it would increase the prevalence of the phenotype relative to teh prevalence of the genotype, then yes. That's what I said. But that's not really the "mystery" here.

or quasi-inherited traits that do provide a competitive advantage (e.g. being from Europe).

Don't understand what you mean here.

I mean that a possible scenario is: small tribe acquires high prevalence of blue eyes genes, then for reasons unrelated to eye color said tribe proceeds to become very successful and large, thus increasing the prevalence of the genotype despite its lack of inherent competitive advantage.

[Riesstiu IV]

Its rarer cuz WWII sent millions of blue eyed people to their grave's. So Hitler is to blame.

[KrazyHorse]

Kuci, that scenario still requires that large numbers of a given tribe get blue eye gene for no particular reason. If we assume blue eyedness is still a simple mutation then there's no reason to assume that large numbers of any given tribe will get it. There will be a constant core of blue eyes in a tribe. We now need them to rise to dominance in their own tribe, then have that tribe take over half the world, and all for no particular reason.

[KrazyHorse]

In other words, that's obviously possible, but not plausible. And is no more plausible than if we didn't pay any attention to sexual self-segregation of blue eyes.

[Kuciwalker]

Kuci, that scenario still requires that large numbers of a given tribe get blue eye gene for no particular reason. If we assume blue eyedness is still a simple mutation then there's no reason to assume that large numbers of any given tribe will get it. There will be a constant core of blue eyes in a tribe. We now need them to rise to dominance in their own tribe, then have that tribe take over half the world, and all for no particular reason.

If the tribe started out small enough it's certainly plausible.

[KrazyHorse]

The smaller the initial size of the tribe the more remote the chances it takes over the world, Kuci.

Breaking the probability up into two pieces (individual to tribe, tribe to region/world) doesn't gain you anything, as far as I can see.

[Kuciwalker]

The smaller the initial size of the tribe the more remote the chances it takes over the world, Kuci.

Breaking the probability up into two pieces (individual to tribe, tribe to region/world) doesn't gain you anything, as far as I can see.

1) I know nothing about the historical population of Europe in the times when this couldn't happened; it's plausible to me that a very small tribe of original Scandinavians got this and proceeded to kill the 5 other original Scandinavian tribes or w/e.

2) In general, it would be a lot more likely for a small tribe to, over thousands of years, expand to a big one than for a noncompetitive genotype to, through pure random mutation, end up in some large % of a large population.

Breaking the probability up into two pieces (individual to tribe, tribe to region/world) doesn't gain you anything, as far as I can see.

Sure. Very early tribes (before they started filling up space) could have been very small but gotten historically a lot larger before they started wiping each other out in earnest.

Also, we're hypothesizing that this particular tribe had quasi-inheritable traits that did provide a significant competititve advantage.

[KrazyHorse]

2) In general, it would be a lot more likely for a small tribe to, over thousands of years, expand to a big one than for a noncompetitive genotype to, through pure random mutation, end up in some large % of a large population.

sqrt(N1*N2) = sqrt(N1)*sqrt(N2)