5 ms·

Why Sex? To Keep Parasites at Bay, of Course

45 points by jkuria 15y ago

deleted 15y ago
[deleted]
ScottBurson 15y ago
> (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 15y ago
  Most organisms play multiple roles, too.
- sliverstorm 15y ago
  The worm adjusts its genes to target the prevailing clone (via sex). This is why.
- sliverstorm 15y 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.
  - praptak 15y 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 15y ago
  Perhaps the worms themselves are vulnerable to smaller parasites.
GavinB 15y 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 15y ago
  Yes, it's okay, but you still have some explaining to do. Science is explaining.
  - phogster 15y ago
    Yes, but that happens when the theory is proposed, not when it's disproved.
StavrosK 15y ago
Did anyone else notice that the two theories aren't mutually exclusive? Renders the article sort of moot...
- jkuria 15y 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 15y ago
  Exactly! Seems like politics are at play here, which is a shame really.
iwwr 15y 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 15y 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.
- praptak 15y 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 15y ago
  Yeast could sort of be described as having 3 genders: https://secure.wikimedia.org/wikipedia/en/wiki/Mating_of_yeast 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 15y 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 15y ago
  with the dual helix 2 sexes seam a good match for matching dna.
  - mv 15y 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 15y ago
  If I recall correctly, it was in his book The Red Queen where he mentions that some mushrooms have 17 sexes.
akkartik 15y 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.

45 points by jkuria 15y ago

deleted 15y ago

[deleted]

> (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 15y ago
Most organisms play multiple roles, too.
sliverstorm 15y ago
The worm adjusts its genes to target the prevailing clone (via sex). This is why.
sliverstorm 15y 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.
- praptak 15y 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 15y ago
Perhaps the worms themselves are vulnerable to smaller parasites.

GavinB 15y 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 15y ago
Yes, it's okay, but you still have some explaining to do. Science is explaining.
- phogster 15y ago
  Yes, but that happens when the theory is proposed, not when it's disproved.

StavrosK 15y ago

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

jkuria 15y 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 15y ago
Exactly! Seems like politics are at play here, which is a shame really.

iwwr 15y 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 15y 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.

praptak 15y 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 15y ago
Yeast could sort of be described as having 3 genders: https://secure.wikimedia.org/wikipedia/en/wiki/Mating_of_yeast 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 15y 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 15y ago
with the dual helix 2 sexes seam a good match for matching dna.
- mv 15y 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 15y ago
If I recall correctly, it was in his book The Red Queen where he mentions that some mushrooms have 17 sexes.

akkartik 15y 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.