Freethought & Rationalism Archive

NZAmoeba · 11-02-2003, 03:35 PM

Its not intentionally selected for or against... it just gets phased out as the population evolves due to statistics.

only 4% are bb, that bb is crutial to blonde existance. the large majority is BB, b genes are rare.

a BB with a bb with make only Bb kids. then when those Bb kids statisticly go with BB's, then the b only has a 1 in 4 chance of survival.

the dominance, and high frequency of the B over the b gene, is why b stands a risk of eventually dissapearing... but not for MANY more generations.

So as i said before, its not intentionally selected for or against, it just happens.

Jesse · 11-02-2003, 03:57 PM

NZamoeba:
Its not intentionally selected for or against... it just gets phased out as the population evolves due to statistics.

No, statistics says that in a large population with random mating and no selective advantage to either gene, the ratio will stabilize at 64% BB, 32% Bb, and 4% bb. Read the explanation in the link on the Hardy-Weinberg equilibrium I gave.

NZamoeba:
only 4% are bb, that bb is crutial to blonde existance. the large majority is BB, b genes are rare.

Yes, it's rare, but that 4% bb is a stable equilibrium. If the population starts out with 10% bb, the percentage of bb will tend to decrease until it reaches 4%, then stop decreasing; if the population starts with 1% bb, the percentage of bb will tend to increase until it reaches 4%, then stop increasing. That's what's predicted by statistics as long as all the necessary conditions (no selective advantage to either gene, random mating, and a statistically large population) hold.

edit: sorry, this only holds for numbers they gave in that article, where 0.8 of the genes were B and 0.2 were b. In general, if p is the proportion of B and q is the proportion of b, then the Hardy-Weinberg equilibrium will be BB = p^2, Bb = 2pq, and bb = q^2. So, for example, if 70% of the genes were B and 30% were b, you'd have a stable equilibrium at BB = 0.7^2 = 0.49, Bb = 2(0.7)(0.3) = 0.42, and bb = 0.3^2 = 0.09

faust · 11-02-2003, 06:50 PM

I've seen this report before somewhere. I was pretty sure it was an urban legend. Either that or a spoof/hoax designed to be picked up.
I'll update if i find out the source.

NZAmoeba · 11-02-2003, 07:08 PM

ah, I didn't read the link, I just assumed the 62/32/4% were current figures... not an equilibrium figure...

faust · 11-02-2003, 07:09 PM

You guys got hoaxed!!

Blondes Don't Face Extinction, Sloppy Journalists Should

Quote:

Not according to the WHO which told the Post that there is no such study and moreover, that most journalists didn't bother to check with them before running with the story.

Quote:

The WHO told the Post they traced the fictitious story to a German wire service, which based it on a two-year-old article in the German women's magazine Allegra. The story cited a WHO anthropologist who, Harding said, she could find no record of any such man having worked for the WHO.

Bam!

Aethari · 11-02-2003, 09:02 PM

It is perfectly possibly for an allele to get 'purged' from a population by random genetic fixation, rather than from any sort of selective force. However, while my knowledge here is limited, I have been told it is notoriously difficult to completely eliminate any allele from a gene pool by fixation alone-- you'll always have a few carriers left over here and there.

~Aethari

Jet Black · 11-03-2003, 11:04 AM

is it intentional irony that as soon as I closed that article I got a popup from that site featuring a bottle blonde?

MBS · 11-03-2003, 08:36 PM

Quote:

Originally posted by NZAmoeba

when you get a BB with a Bb though, thats when the b starts to be phased out. You only have a 1 in 4 chance that the kid will keep the b gene, in the other 3, it'll be lost forever because they'll be BB, and even then, the 1 kid will still have brown hair.

I think it would still be a 2 in 4 (50%) chance of passing the b.

...|.B...B
------------
B.|.BB.BB
...|
b.|.Bb.Bb

There are many genetic disorders which are recessive genes whose occurence remains steady despite a very low percentage in the general population. Anyone who has the gene has at least a 50% chance of passing it on, so it survives.

Even if the blond gene became as rare an albino gene, it still wouldn't dissappear completely, short of a mass extinction of the human race.

ComestibleVenom · 11-05-2003, 10:19 AM

Quote:

Originally posted by elwoodblues

The trend is fucking until everyone looks the same. But that's a far off thing, and will only be approached asymptotically, not totally.

I don't see this trend elwood, nor do I see it as a safe bet for the future.

NZAmoeba · 11-05-2003, 12:51 PM

Quote:

I think it would still be a 2 in 4 (50%) chance of passing the b.

oops, you're right, that'll teach to me work things out in my head...

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11-02-2003, 03:35 PM	#11
NZAmoeba Regular Member Join Date: Apr 2003 Location: New Zealand Posts: 478	Its not intentionally selected for or against... it just gets phased out as the population evolves due to statistics. only 4% are bb, that bb is crutial to blonde existance. the large majority is BB, b genes are rare. a BB with a bb with make only Bb kids. then when those Bb kids statisticly go with BB's, then the b only has a 1 in 4 chance of survival. the dominance, and high frequency of the B over the b gene, is why b stands a risk of eventually dissapearing... but not for MANY more generations. So as i said before, its not intentionally selected for or against, it just happens.

11-02-2003, 03:57 PM	#12
Jesse Moderator - Science Discussions Join Date: Feb 2001 Location: Providence, RI, USA Posts: 9,908	NZamoeba: Its not intentionally selected for or against... it just gets phased out as the population evolves due to statistics. No, statistics says that in a large population with random mating and no selective advantage to either gene, the ratio will stabilize at 64% BB, 32% Bb, and 4% bb. Read the explanation in the link on the Hardy-Weinberg equilibrium I gave. NZamoeba: only 4% are bb, that bb is crutial to blonde existance. the large majority is BB, b genes are rare. Yes, it's rare, but that 4% bb is a stable equilibrium. If the population starts out with 10% bb, the percentage of bb will tend to decrease until it reaches 4%, then stop decreasing; if the population starts with 1% bb, the percentage of bb will tend to increase until it reaches 4%, then stop increasing. That's what's predicted by statistics as long as all the necessary conditions (no selective advantage to either gene, random mating, and a statistically large population) hold. edit: sorry, this only holds for numbers they gave in that article, where 0.8 of the genes were B and 0.2 were b. In general, if p is the proportion of B and q is the proportion of b, then the Hardy-Weinberg equilibrium will be BB = p^2, Bb = 2pq, and bb = q^2. So, for example, if 70% of the genes were B and 30% were b, you'd have a stable equilibrium at BB = 0.7^2 = 0.49, Bb = 2(0.7)(0.3) = 0.42, and bb = 0.3^2 = 0.09

11-02-2003, 06:50 PM	#13
faust Senior Member Join Date: Apr 2003 Location: baton rouge, la Posts: 539	I've seen this report before somewhere. I was pretty sure it was an urban legend. Either that or a spoof/hoax designed to be picked up. I'll update if i find out the source.

11-02-2003, 07:08 PM	#14
NZAmoeba Regular Member Join Date: Apr 2003 Location: New Zealand Posts: 478	ah, I didn't read the link, I just assumed the 62/32/4% were current figures... not an equilibrium figure...

11-02-2003, 09:02 PM	#16
Aethari Veteran Join Date: Aug 2002 Location: Maryland, USA Posts: 1,635	It is perfectly possibly for an allele to get 'purged' from a population by random genetic fixation, rather than from any sort of selective force. However, while my knowledge here is limited, I have been told it is notoriously difficult to completely eliminate any allele from a gene pool by fixation alone-- you'll always have a few carriers left over here and there. ~Aethari

11-03-2003, 11:04 AM	#17
Jet Black Contributor Join Date: Aug 2003 Location: (GSV) Lasting Damage Posts: 10,734	is it intentional irony that as soon as I closed that article I got a popup from that site featuring a bottle blonde?

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