Why Sex? To Keep Parasites at Bay, of Course

http://online.wsj.com/article/SB10001424052970203633104576625152239037650.html

by jkuria • 15 years ago

45 21 15 years ago

online.wsj.com

> (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.

Wuzzy• 15 years ago

Most organisms play multiple roles, too.

sliverstorm2• 15 years ago

The worm adjusts its genes to target the prevailing clone

(via sex). This is why.

sliverstorm2• 15 years ago

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.

praptak2• 15 years ago

> 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.

m-photonic• 15 years ago

Perhaps the worms themselves are vulnerable to smaller parasites.

GavinB• 15 years ago

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.

baddox• 15 years ago

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

phogster• 15 years ago

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

StavrosK• 15 years ago

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

jkuria• 15 years ago

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.

k33n• 15 years ago

Exactly! Seems like politics are at play here, which is a shame really.

iwwr• 15 years ago

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.

nivertech• 15 years ago

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.

praptak2• 15 years ago

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.

nitrogen• 15 years ago

Yeast could sort of be described as having 3 genders: https://secure.wikimedia.org/wikipedia/en/wiki/Mating_of_yea...

praptak's second paragraph seems like a decent explanation why 2 seems to be the typical number.

VladRussian• 15 years ago

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.

taken11• 15 years ago

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

mv• 15 years ago

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.

shard• 15 years ago

If I recall correctly, it was in his book The Red Queen where he mentions that some mushrooms have 17 sexes.

akkartik• 15 years ago

"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.

Why Sex? To Keep Parasites at Bay, of Course

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