

Why Sex? To Keep Parasites at Bay, of Course - jkuria
http://online.wsj.com/article/SB10001424052970203633104576625152239037650.html

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GavinB
_If you champion a theory and it gets disproved, you have some explaining to
do._

Actually, it's okay to have a theory that gets disproved. That's how the
process is supposed to work.

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baddox
Yes, it's okay, but you still have some explaining to do. Science _is_
explaining.

~~~
phogster
Yes, but that happens when the theory is proposed, not when it's disproved.

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ScottBurson
> (the worm has sex inside the duck)

So this theory explains why the snails have sex, but it doesn't so clearly
explain why the worms have sex -- since they _are_ the parasites in question.

I don't know why there has to be just one reason that organisms have sex. If
there's anything we know about biological systems, it's that most structures
serve multiple functions.

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sliverstorm
_I don't know why there has to be just one reason that organisms have sex_

I'm inclined to agree. I'm not sure why the author limits themselves to
parasites. Parasites are not the only selective pressure that can be addressed
via genetic recombination.

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praptak
> I'm not sure why the author limits themselves to parasites.

Parasites are distinct from most other selective pressures: they constantly
adjust to whatever adaptations the host has come up with. Other pressures do
not have this property - the desert doesn't get much drier because some plants
adapted to the lack of water.

This also explains why worms have sex - even if they don't have parasites of
their own (they most probably do), they need to adapt to their hosts'
countermeasures.

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StavrosK
Did anyone else notice that the two theories aren't mutually exclusive?
Renders the article sort of moot...

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jkuria
thank you for saying this! I re-read the second theory a couple of times and I
wasn't sure I quite got it. It seemed like the difference was a minor
technicality, which made the article much less compelling. Flushing out bad
genes (vulnerable genes) out of the genome so that the next generation is
stronger isn't all that different from changing locks on the cells to protect
against parasites attacking the offspring.

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iwwr
Sexual reproduction allows more than gene shuffling, it permits traits from
multiple lineages to come together in a single individual. Adaptations only
need to be developed in one individual of the gene pool for the descendants of
that population to have a chance to pass it along.

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VladRussian
any theory of sex is incomplete until it addresses why there are 2 sexes (even
if one organizm can carry both sexual organs it is still 2 distinct sexes). It
may seems obvious, yet a science theory must address it scientifically. All
the shuffling, flushing, etc.. of genes would also work in 3, 4, ... sexes
schemas. It will have different statistical distributions and the theory must
prove that whatever goal of sex existence, it is somehow optimal with 2.

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taken11
with the dual helix 2 sexes seam a good match for matching dna.

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mv
no that doesn't at all. Why not have any two humans mate to have offspring?
there are 23 pairs of chromosomes and only 1 pair is sex determining. doesn't
really make sense to have male/female especially since the 'male' physical
characteristics are small enough to be present in a female also.

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nivertech
The real question is, why nobody found yet species with 3 genders? I.e. 1
gender (cloning), 2 genders (sexual), ... 3 genders (hyper-sexual)?

3 genders will allow even more gene shuffling and multiple lineages to come
together in a single individual.

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praptak
You think that finding _one_ suitable partner isn't hard enough already?
Joking aside - the complexity of getting 3 specimens of suitable sexes to
produce offspring is probably what kills this possibility.

And the most benefit in terms of shuffling is between having recombination
(sex) and not having it at all (cloning.) It is not evident to me that there's
significant additional benefit from introducing the hypothetical 3rd sex.

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akkartik
"Red Queen" is one of my all-time favorite books, up there with "The Fates of
Nations" by Paul Colinvaux. Both instantly and completely changed how I saw
the world around me.

