Re: What is the purpose of pheomelanin in skin?

blackhead wrote:
On 24 Nov, 21:21, Tim Tyler <seemy...@xxxxxxxxxxxxxx> wrote:
blackhead wrote:

Does Pheomelanin have some sort of influence in the production of
Vitamin D, for example?
Girls have more pheomelanin than boys. Pheomelanin makes you pink.

Girls use red pigments (e.g. in cheeks and lips) for sexual signalling
purposes - so pheomelanin is probably associated with sexual selection.
This idea is consistent with its presence in red hair.

Is this your theory, or is there some academic credibility to it?

Girls /do/ have more pheomelanin than boys. And pheomelanin /does/ make
you pink. I do not know if the elevations in girls are caused by sexual
selection - but IMO, that's the reason for most such sex differences.

However it is possible that the pheomelanin gene(s) have pleiotropic
effects - and something other than the cosmetic effect is what is
being selected for.

The most obvious pleiotropic effect of pheomelanin seems to be a
greater chance of getting skin cancer, though.

The story of red hair - and its pheomelanin:

``Rees (2004) suggested that the vividness and rarity of red hair
may lead to it becoming desirable in a partner and therefore it
could become more common through sexual selection.

Harding et al (2000) proposed that red hair was not the result
of positive selection but rather occurs due to a lack of negative
selection. In Africa, for example, red hair is selected against
because high levels of sun would be harmful towards fair skin.
However, in Northern Europe this does not happen and so redheads
come about through genetic drift.''

- http://en.wikipedia.org/wiki/Red_hair

Pheomelanin is present in other mammals - and in birds - where
my impression is that it is also used for red colouration,
which is often sex-related.
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