Evolution of sex revisited
Tim Tyler
"Has the mystery of sex been explained at last?"
Pretty severe Red Queen criticisms!
I accessed Sally Otto's referenced paper - to see if it was correct.
It's a computer-model paper, and doesn't describe its algorithm or
provide source code :-(
The paper doesn't say its model is spatialised. Failure to use
a spatialised model is a key mistake in Red Queen models. It is
important for pathogens to be able to track their hosts down the
generations. Spatialisation is one simple way of doing that.
The paper concludes:
``These results show that, when a species must constantly evolve
to stay abreast of surrounding species, the Red Queen does not
maintain high amounts of sex and recombination unless species
interactions induce strong selection per locus.''
ISTM that the whole point of parasites in the model is that they
provide gigantic selection pressures - enough to counter-balance
the cost of sex.
This all seems rather weak to me. Is there any better evidence
against Hamilton's model that I am missing?
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John Edser
Tim Tyler <seem...@googlemail.com> wrote:-
> I accessed Sally Otto's referenced paper - to see if it was correct.
>
> It's a computer-model paper, and doesn't describe its algorithm or
> provide source code :-(
>
> The paper doesn't say its model is spatialised. Failure to use
> a spatialised model is a key mistake in Red Queen models. It is
> important for pathogens to be able to track their hosts down the
> generations. Spatialisation is one simple way of doing that.
>
> The paper concludes:
>
> ``These results show that, when a species must constantly evolve
> to stay abreast of surrounding species, the Red Queen does not
> maintain high amounts of sex and recombination unless species
> interactions induce strong selection per locus.''
>
> ISTM that the whole point of parasites in the model is that they
> provide gigantic selection pressures - enough to counter-balance
> the cost of sex.
>
> This all seems rather weak to me. Is there any better evidence
> against Hamilton's model that I am missing?
JE:-
1) Simplified/oversimplified modeling simulations cannot validly
_replace_ bona fide theories based on empirical observation.
2) Hamilton's inclusive fitness was and remains just an oversimplified
model of Darwinism that has been consistently misused, i.e. it is not a
bona fide theory of anything. The proof: Hamilton's rule does not refer
to a single constant, even implicitly. Mathematics is not and will never
be, a science.
Regards,
John Edser
Independent Researcher
William Morse
There was a brief review in the 5 June Science (p. 1254) of this
question. That article indicated that the explanation for sex includes
the Red Queen but also includes a number of other factors, such as the
improved fitness from recombination and a model that shows that "genes
for sex spread thanks to their own selfish drive to generate ever more
copies of themselves".
Yours,
Bill Morse
Tim Tyler
> Tim Tyler wrote:
>> This all seems rather weak to me. Is there any better evidence
>> against Hamilton's model that I am missing?
>
> There was a brief review in the 5 June Science (p. 1254) of this
> question. That article indicated that the explanation for sex includes
> the Red Queen but also includes a number of other factors, such as the
> improved fitness from recombination [...]
That is not really much of a different theory. The Red Queen is
a theory of "improved fitness from recombination". However the
"improved fitness" has to be improved by a factor of more than two.
Only parasites can provide such an enormous selective pressure.
DNA repair is the other theory that is powerful enough alone to
account for the costs of sex. However, an ecological examination
of the cases where each theory applies seems quite favourable to
Hamilton. Hamilton is bullish about the issue:
"So for the present I just bow to Rick's truths of DNA repair as
undoubtedly part of what will be our full story. But let us wait
and see whose "truths", in the end are more primary and have the
better survival."
- W.D.Hamilton, N.R.O.G v2 - Evoultion of Sex, page 104-105.
> and a model that shows that "genes for sex spread thanks to
> their own selfish drive to generate ever more copies of themselves".
That sounds as though it is either trivially true or wrong. *All*
genes in a sense spread "thanks to their own selfish drive to
generate ever more copies of themselves". However, if that is a
claim that sex is not adaptive w.r.t. to the other nuclear genes,
then that seems to be just a confusion about what the term "sex"
means - or at least *should* mean.
Sex is not a disease:
http://alife.co.uk/essays/sex_is_not_a_disease/
Sex has got to be an adaptation - it can't be neutral, its effects
on fitness are too big - and there are things like facultative
sexual reproduction to explain.