From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Fri Nov 29 2002 - 07:13:54 MST
On Fri, 29 Nov 2002, Anders Sandberg wrote:
> i.e. Gilbert's syndrome provides a tiny disadvantage. There might
> be some anti-ageing component, but I doubt it - that would likely
> in historic times have made the gene have positive fitness and it
> would have become even more common.
Anders, I think you have to think this through very carefully
in terms of antagonistic pliotropy and mate selection.
Gilbert's syndrome might provide a quite strong anti-ageing
component -- but might provide a quite negative mate selection
component. Human (and perhaps all animal) mate selection criteria
are biased towards those who appear "healthy" (stronger, etc.).
An anti-ageing gene that turns you yellow may have strong self
benefits but decrease your probability of being desirable as
a mate! Around Greenlake in Seattle, there is a population of
Red-winged blackbirds. I'm not an expert in this but it
appears that every spring the males develop striking red
feather patches on their wings. But later (presumably
after mating season) these patches seem to fade. One
would suspect that female Red-winged blackbirds are strongly
attracted to the most brightly colored males. It seems
likely that the development of an anti-ageing gene that
produced blue feather patches would have a difficult time
penetrating into the population.
There must be a very strong fitness advantage for a trait to
overcome a mate selection bias disadvantage for it to become
common in a population. For example why do we not have
more red-haired people in populations around the world?
Or why aren't there as many blonds in Nigeria as there
are in Sweeden? (I doubt skin melanin production is
tightly linked to hair color -- skin melanin has an
anti-cancer selection effect while hair color seems likely
to only have a mating effect).
This is a very complex topic with respect to population
genetics and I suspect there are lots of traits with
positive anti-ageing components that would have negative
mate selection components.
Robert
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