Thursday, January 31, 2013

Are blonde's dying out?



Permit me a repeat but I thought some of you may find this interesting. The idea that 'recessive' genes will somehow be lost from the population (simply because they are recessive) is quite persistent. They may be lost by genetic drift or by selection but, as you should have seen today, being recessive actually helps you if you are at a selective disadvantage because the heterozygotes are not selected against and they each contain a copy of the recessive allele.

In 2002 there was a series of stories in the press announcing that blondes were dying out. A typical story from the BBC:
Blondes 'to die out in 200 years'.
The proposed mechanism for this loss of blondes was simply that the gene was recessive

..too few people now carry the gene for blondes to last beyond the next two centuries.   The problem is that blonde hair is caused by a recessive gene.


But, as we saw, Hardy and Weinberg cleared that up for us over 100 years ago. An allele will not decline in frequency simply because it is recessive.

The story appeared to originate with the World Health Organization, although suspiciously, no scientists were named. It subsequently turned out the whole story was dubious if not fake. The WHO eventually issued a press release: 

''W.H.O. has no knowledge of how these news reports originated,'' said  the organization, an agency of the United Nations based in Geneva, ''but  would like to stress that we have no opinion of the future existence of  blonds.''

Because news stories tend to have a cyclical life of their own this story has resurfaced a number of times since 2002.

Skip forward a few years  to 2005 and a series of press reports on a similar fate for redheads:
Gingers extinct in 100 years, say scientists    
This time the story can be chased back to a misreporting of a story in National Geographic and the 'Oxford Hair Foundation' - funded by a manufacturer of hair dye.

I used to have blond hair but it died out....

No comments: