The idea that blonds are dumb comes from a warning that bleach reduces intelligence. It was never meant that natural blonds were dumb it was suppose to be women that dyed their hair blond were dumb. It just evolved into people generalizing all blonds.

My MOTHER first poured peroxide on my head at 12 in the bathtub (issues?;). I otherwise was born with med brown hair and green eyes (Russian, German, Slovakian, English, Irish, and French). I continued dying my hair through high school by spraying Sun-in on it or box-dying it and then through college going to the salon and was a blonde who had a lot of fun ;)for 15 years. I'm 27 and last year stopped with the blonding when I finally got a "chemical cut" that took out 1/4 of my hair a few inches from the scalp (luckily in the back). I've been for the most part happy with being a brunette for the past 9 mos with recently chopped (to even it all out:) shoulder length hair. But after a recent break-up I am like a predictable robot! having my hair dyed blonde again.

I wonder which is more attractive: long, healthy brown hair or shoulder length but really blonde hair? I can't really do long and blonde forever, apparently :(

Blonde would probably be better either way from my experience ;)

I'm a big advocate for evolutionary psychology and the way it can be applied to many aspects of our modern attitudes and behaviours, but I think a relevant question is why did blonde hair only develop in Northern Europe when there would have been other parts of the ancestral world that were also frigidly cold for most of the year, requiring women to rug and not show their "firm breasts".
Why do Northern Chinese, Japanese, native Siberians and native North Americans all have black hair when these places were equally as cold as Scandanavia.

If being blonde was such a strong indicator for reproductive success, why do 90% of the modern human population have jet black hair and why do even most younger Europeans have hair in varying shades of brown, not blonde?

You seem to have misunderstood evolution. Traits don't appear with the goal to maximize fitness. Traits appear by variation and mutation, and some survive, if they, by chance, increase fitness in some way.

If blond hair did evolve in a cold environment, it was not a reaction to this environment: "I can no longer show my fitness (fertility), I need to show my fitness somehow, blond hair will work well". It was a random variation/mutation which created blond hair which had by chance the effect of increasing attraction of the opposite sex.

The gene for Blond hair is thought to have appeared about 11,000 years ago, probably as a random mutation through genetic drift (same goes for red hair, though it appears to date back farther). That's 9000 BCE, definitely not enough time to have any sort of evolutionary impact on humans. There can be no instinct developed within 9000 years of sexual selection. Men chose blond hair back then because it was distinctive and made the woman stand out from the crowd. We were definitely cognizant enough at that time to know if a certain person had been around the block a few times. And if we were not, where is the fine line between being aware enough to track a women's hair color for signs of age (as opposed to say skin, teeth, and other physical factors that have been around longer and definitely have a natural evolutionary preference/youth factor) and being able to keep track of how long the woman herself has been around.

Also, red hair has just as much of an age factor as does blond hair. It changes color with age, but do we see red hair as the perfect ideal? No. Because blond hair doesn't have some of the health issues associated with it that red hair does and because we've been socialized since the dawn of western civilization to like blond hair. Just because the Romans were doing it without peroxide (seriously how is that an argument for the evolutionariness of it? the Ancient civilizations were VERY good at herbal stuff, alarmingly so) doesn't mean women weren't being socialized into wanting to look like Aphrodite and men weren't being socializid to want Aphrodite look-a-likes.

For both men & women, black haired people have the lowest average IQ.

They also have a narrower distribution with far less genius level IQs.

Toby Keith, yes the country singer, has said it best: "Why do blonds seam to have more fun? Because they are easiest to spot in the dark." (Which is when mating generally happens). End of story- if you are big strong soldier, who are you going to rape while pillaging a village at night... some easy to spot blond. Which is probably why the Scandinavians (formerly the Vikings who were terrific pillagers) have soooooo many blonds, or why there are so many blonds in the Northern parts of the former Roman empire--- blonds were easiest to catch in the Germanic states. And now that pillaging and raping has lost its faddishness- most blonds don't reproduce as much, and statistically most blonds are FAKE! Don't reflect modern values on a world that wasn't anything like its today- there just weren't that many love matches. Marriages and mating was a ritual of force, conquered people didn't get to chose their mates, the big tough guys got to chose their mates, or the kings, tribal leader. Blonds were trophy wives in the earliest sense of the word- WAR TROPHIES. And as trophies they had to mate. Thus the spreading of the genetic malfunction we know as being blond comes from the progeny of blond trophy wives later being in the position to also rape and pillage.

How can black African men and East Asian men be genetically predisposed to prefer blondes, if there were no blonde women in their original populations? Non-Caucasian females don't have light-coloured hair when they are babies, so how could (late) Scandinavian selection transfer over to black and Asian men's genes?

Wouldn't blonde hair signal albinism instead within the original black and Asian populations?

Sexual selection for blondes? I think you're right, but there is more to European hair than blondes.
Diversity more than blondism in European hair colours is the anomaly
Here's the 2006 paper that gives an explaination.

I find that studies like this show an extremely narrow-minded viewpoint. The blonde-hair, big-bust beauty ideal cannot logically be chalked up to evolutionary psychology alone for two main reasons:

1) Calling blonde hair the evolutionary ideal is extreme ethnocentricism. Most of the world's population cannot even produce blonde hair, and this includes people in cold places other than Northern Europe - what about naturally dark-haired groups living in Siberia?

2) This ideal has NOT been the ideal forever, not even in Western culture. For example, if you look at classical Greek or Roman statues, and the nude paintings from the Middle Ages, Renaissance and later, you'll see that most of the women have a smaller chest. Even in Rubens paintings that show 'voluptuous' women most of them have a relatively small bust for their size. If big boobs are the ultimate ideal, how do you explain that?

And it's interesting that you mention the extreme aversion to redheads, because red hair was often held as the ideal instead of blonde - look at Titian, Botticelli, or the pre-Raphaelite painters.

I can't believe this sort of thing gets published and declared as the scientific truth, when historical knowledge of beauty ideals would disprove it. The beauty ideals of recent Western culture are not the beauty ideals of the entire world, or even the entire history of Western culture, so it seems ridiculous at best to try and justify them on an evolutionary basis.