No more blondes? No!

[eric_lippert]

Snopes today has an interesting article about a persistent urban myth that human blondes are gradually going extinct. However they do not actually go into any of the scientific and mathematical arguments that show why this is extremely unlikely. Two mechanisms are proposed in the myths - that blondes are going extinct because blondeness is

Comments

[adventure_girl]

You're mostly right...

Here's the thing. Any time you are uncertain of the genotype of an organism, you must allow the possibility of heterozygocity as well as homozygocity, therefore, basing your conclusions on the F1 generation is basing your conclusions on half of the experiment. You can't have a good idea of the genotype of the P generation until you reach the F2.

Punnet squares 101:
http://anthro.palomar.edu/mendel/mendel_2.htm

Eye color and hair color (as well as skin color) are weird ones, however. First of all, there is the issue of codominance. (You may be familiar with the principle: http://www.borg.com/~lubehawk/inccodom.htm) Additionally, pigmentations are a result of levels and types of amino acids produced by the codons of the helices of the alleles in reference. Basically, the genes you get code for codon patterns, and what we see as "blonde" or "green" really translates to a certain number, percentage, and location of various amino acids in combination with each other. (Yay, codons! http://waynesword.palomar.edu/codons.htm) So you don't really get a single gene which says "green", etc.

But then, there is another element to consider... phenotype = genotype + environmental influence. In short, pale skin is maladaptive in subsaharan Africa or Central America. And, I don't know, maybe blonde hair is maladaptive somewhere... So, if you're blonde in subsaharan Africa, you'll get eaten by lions (or something), and therefore not allowed the opportunity to reproduce. In actuality, all light pigmentation was originally a maladaptive quality in most of the world (Why, I don't remember now. Maybe because white people die of skin cancer and blondes are dumb.)

Okay, enough ranting... Point being that while you're not incorrect, you are addressing half of the heritability equation, and your explanation of genomics is a little simplified. Of course, the article you sited has the same flaw. You're not incorrect, but the logic is incomplete.

(P.S. Sorry... I realize this is a totally unnecessary rant... but then, that's what I do. My students were subjected to this very thing today -- with more to come, those poor unlucky bastards.)