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In article <1992Dec5.002034.1 at nickel.laurentian.ca> s1400070 at nickel.laurentian.ca writes:
> Hi. I'm looking for some information into the validity of the theory that
>sexual reproduction has evolved as a defence against the actions of parasites.
>Since most parasitic invaders reproduce assexually and may have many generations
>in the course of the host organisms's life, one would expect that natural
>selection would play a more important role in the parasite population.
>Therefore, evolution would proceed more quickly in parasite populations. Hence,
>the development of sexual reproduction as a means evening the odds.
>Its a tempting theory. Does it make sense to anyone else?
Makes perfect sense to me. Then again, that's what I study. The
theory is called the Red Queen hypothesis (name stolen from Leigh Van
Valen's macroevolutionary hypothesis, which was stolen from _Through
the Looking Glass_). RQ doesn't explain the _development_ (i.e.
origin) of sex so much as the _maintenance_ of sex in the face of the
twofold cost of anisogamy. Basically, the advantage of sex comes from
the coevolution of parasites and their hosts: since parasites can
evolve faster than their hosts, the parasites have the upper hand in
getting around the host's self-nonself recognition system. So, the
best the host can do is to mix up "self" as much as possible from
generation to generation, through sex. Since the parasite population
tracks the most common host genotype, it is advantageous at the
individual level to produce rare offspring.
I don't have my bibliography with me right now; I'll post some
complete references later, but for now, you may want to look up papers
by John Jaenike, W. D. Hamilton, and Curt Lively.
> John Antonioni
> Sudbury, Canada
--
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