N-body reproduction

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N-body reproduction

Postby Robert'); DROP TABLE *; » Thu Nov 04, 2010 9:37 pm UTC

Would there by any advantage to reproductive biology that works in a way that 3+ members can reproduce at once? Or is there a good reason that nature stuck to 1 and 2?
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Re: N-body reproduction

Postby Sir_Elderberry » Thu Nov 04, 2010 9:55 pm UTC

(Not a biologist. What follows is speculation.) Possibly a matter of balance. I know there's a sort of balance in evolution--too much genetic mixing and you don't get a stable gene pool, mutations, etc. Too little and, well, you can't adapt. So maybe two is just the right number as far as being able to keep up some rate of mixing but not too much.

EDIT: Also, remember that biology doesn't have a guiding hand. It's possible that N-body reproduction is perfectly viable, but it never happened.
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Re: N-body reproduction

Postby Izawwlgood » Thu Nov 04, 2010 10:04 pm UTC

My first thought is the depth and breadth of diversity of reproductive strategies developed with a two sex reproductive system, centered around finding, courting, maintaining, and protecting mates and offspring, and my god man, you want to make that MORE complex?

One possible benefit of such a system, however, would be a triallelic genome; recessive mutations would be that much less likely (uh... no, i'm not even going to start the punnet cube on that, someone else can do it). This would immediately result in a more energetically demanding system of cell division, as approximately 50% more genetic material would need be duplicated from what we currently have.

EDIT: Oh... Punnet Cube... Yeah, so it'd be a 1/9 chance for 3x Mmm parents to produce recessive mutations, right? As opposed to a the 1/4th chance.

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Re: N-body reproduction

Postby nehpest » Thu Nov 04, 2010 10:12 pm UTC

Izawwlgood wrote:My first thought is the depth and breadth of diversity of reproductive strategies developed with a two sex reproductive system, centered around finding, courting, maintaining, and protecting mates and offspring, and my god man, you want to make that MORE complex?

One possible benefit of such a system, however, would be a triallelic genome; recessive mutations would be that much less likely (uh... no, i'm not even going to start the punnet cube on that, someone else can do it). This would immediately result in a more energetically demanding system of cell division, as approximately 50% more genetic material would need be duplicated from what we currently have.


I think we have a winner here. Some cursory Googling brings me the term "index of reproductive effort" and the data that a) asexual reproduction (1-body) has a much lower IRE than 2-body sexual reproduction, and that b) as an example IRE, the IRE for the symbiotic sea anemone Aiptasia pulchella ranges from 0.004 to 0.044 (The energetics of asexual reproduction: Pedal laceration in the symbiotic sea anemone Aiptasia pulchella, Hunter 1984).

It seems a reasonable hypothesis that triallelic genomes, and the increased reproductive effort, would bring less survival benefit than our current double helix arrangement, but someone more biologically informed will have to verify this.
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Re: N-body reproduction

Postby Izawwlgood » Thu Nov 04, 2010 10:25 pm UTC

I just want to point out that triallelic genomes has nothing to do with the double helix. I think you meant 'chromosome PAIRS'.
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Re: N-body reproduction

Postby GeorgeH » Thu Nov 04, 2010 10:33 pm UTC

Also not a biologist, but more breeders would reduce the chance of a beneficial mutation being passed on (for an equivalent number of breeding events) so an orgynism would probably go extinct relatively quickly.

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Re: N-body reproduction

Postby BlackSails » Thu Nov 04, 2010 10:41 pm UTC

Same reason that termolecular reactions are so rare. Its hard to get 3 things together at the same time. Right now, two animals need to find each other compatible. With 3-mating, 3 animals each need to find two others compatible. With 4-mating, 4 animals need to find 3 others compatible. It increases quite fast. 2-mating isnt even always better than asexual reproduction, so its hard to imagine that 3-mating would ever be worth it.

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Re: N-body reproduction

Postby Zamfir » Fri Nov 05, 2010 4:32 pm UTC

"Player of Games" by Iain Banks had a trisexual hominid alien race. The mechanism was that one sex impregnated the middle sex, who then in turn put the embryo in a third sex, where some retrovirus or so made the last changes to the hereditary material.

That at least solves the "trimolecular reaction problem": those might be rare, but a chain of two bimolecular reactions is easy.

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Re: N-body reproduction

Postby Izawwlgood » Fri Nov 05, 2010 7:35 pm UTC

It's not entirely unreasonable to imagine a spawning system, wherein the gametes of three individuals are required. Such a system would probably be, actually, more favorable in terms of avoiding recessive mutations.

My guess is evolution of such a system would occur much more slowly; while there's still room for reshuffling, the chance of any given trait being passed on is reduced.
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Re: N-body reproduction

Postby Coffee » Fri Nov 05, 2010 9:48 pm UTC

And if you thought genomic conflict was a complicated aspect of evolutionary biology on a two-sex system...
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Re: N-body reproduction

Postby sikyon » Sat Nov 06, 2010 3:04 am UTC

If I understand it correctly, 2 sex systems allow creatures to share DNA more eaisly which increases mutation rate and natural selection rate, as well as helping ot correct for recessive genes. The tradeoff is that it costs more energy and you can't reproduce as fast. I cannot see any advantage that a 3 sex system, which is more complicated, would give you that 2 sex systems do not.

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Re: N-body reproduction

Postby Robert'); DROP TABLE *; » Sat Nov 06, 2010 10:46 pm UTC

Would 3-mating necessarily imply 3 sexes, or would it work with 3 androgynous individuals?

Izawwlgood wrote:My first thought is the depth and breadth of diversity of reproductive strategies developed with a two sex reproductive system, centered around finding, courting, maintaining, and protecting mates and offspring, and my god man, you want to make that MORE complex?

Yes, because I am a mad physicist-turned-sci-fi writer. :P
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Re: N-body reproduction

Postby Izawwlgood » Sat Nov 06, 2010 11:33 pm UTC

I think in the terms that we've been sort of discussing, it would imply 3 different sexes. If you're suggesting something more along the lines of sex switching, or say, a female, and two possible males, you're delving into something that is still ostensibly a 2-sex system, and is in fact, practiced on Earth already (not the three parent part of course...)

AFAIK, there's nothing on the planet that utilizes an actual factual, 3-sex system. If you're writing stuff, and want some lose details as to how it could happen, I could offer some notions that may be... feasible?

I've read a handful of stories that have 3-sex aliens. There are some neat things it creates in terms of gender roles.
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Re: N-body reproduction

Postby Soralin » Sun Nov 07, 2010 3:32 am UTC

What about single celled organisms that can transfer genetic material between themselves? If that happens multiple times for a specific organism before it produces a copy of itself, that could sort of technically fit.

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Re: N-body reproduction

Postby Izawwlgood » Sun Nov 07, 2010 3:55 am UTC

It would, but typically this is a unidirectional process, or, involves a binary mating type.
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