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I am attempting to devise a mechanism whereby a species may reproduce in a communal manner. A number of individuals, ranging from two to arbitrarily high, may contribute gametes to a mass spawning and the resulting offspring will be genetically related to all of the parents who contributed. This would potentially allow for predominantly collectivist social structures as with social insects without limiting the population of reproductive individuals or resorting to an r-selection strategy where paternal relations are unknown and family groups could not develop. The intent is for any given community to function as one gigantic biological family.

As far as I am aware, no such reproductive cycle exists on Earth. Earthly life only ever has one or two parents contributing nuclear DNA.

EDIT: The problem I run into is with the cellular machinery. I assume the process would be similar to alternation of generations where the dominant generation has X-ploidy and the subsidiary generation of syncytia divides into X-ploid zygotes. How would the gametes would merge? How would the syncytia sort the chromosomes into viable zygotes? What would be an ideal ploidy under this system?

EDIT: One of the few examples in fiction I can think of are the Than-Thre-Kull from Gene Roddenberry's Andromeda. Even if it is unlikely to evolve, there must be some logical explanation? I read the paper "Genetic algorithms with multi-parent recombination" which convinced me it's possible, but it was concerned with computer science and not biology.

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    $\begingroup$ I'm not sure that this will work since it's so unspecific. When you're talking about biological systems, at a low level, they're very specific, and such flexibility would be difficult to evolve, especially considering that the maximum benefit/cost from sexual reproduction with n partners occurs at n = 2. $\endgroup$ – Monty Wild May 20 '16 at 1:39
  • $\begingroup$ The Drummers from Neil Stephenson's Diamond Age may be a good source for you. In that case, the information carrying material was a bunch of nanomachines, rather than organic gametes, but the drummer's ritual near the end of the book would qualify. $\endgroup$ – Cort Ammon - Reinstate Monica May 20 '16 at 6:07
  • $\begingroup$ @CortAmmon, nanomachines are designed, as are genetic algorithms. This probably couldn't happen as an evolved mechanism. $\endgroup$ – Monty Wild May 20 '16 at 6:49
  • $\begingroup$ This maybe will be good for situations where species should almost extinct in short time, with longer relaxation time and gain population number again. And repeating that process on regular basis. Simple evolution works on big numbers. $\endgroup$ – MolbOrg May 21 '16 at 2:12
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Instead of actually mixing an arbitrary number of gametes, give the organism a microscopic caste or morph capable of reproduction among themselves.

Consider this: The adult organisms all drop their gametes together in a spawning pool, where they combine at random in the normal sexual manner. However, instead of developing into the large, terrestrial adults, the zygotes become microscopic animals that mature very quickly and proceed to breed among themselves, producing more microscopic offspring. This continues for several generations, before an internal or external trigger causes the microscopic morph to instead produce tadpoles that develop into the large, (presumably intelligent?) adults.

By this point, the creatures who crawl out of the spawning pool will technically be several generations removed from their 'parents' and will therefore have an effectively random mix of genes from all the parents who contributed to the original pool.

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    $\begingroup$ My thought exactly: the OP is describing the longer-scale view of a population. Make it happen quickly with the same effect. Advantages: finding an optimal combination before investing very much in growth, and preventing non-optimals from entering the main population. $\endgroup$ – JDługosz May 22 '16 at 20:06
  • $\begingroup$ This form of heterogamy seems the most efficient mechanism for multi-parent genetic mixing in the absence of a mechanism to combine multiple gametes directly. Even better, it sounds like something that could conceivably develop among zooids in our own oceans. $\endgroup$ – Anonymous May 23 '16 at 13:14
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The main issue with evolution is that it's all about concurrency in reproduction. So it would go in directions that an individual would aim for maximum of offspring and also might care for his offspring to improve their chances. A simple solution would be to construct a society which postulates rules where this is not possible - say to reduce conflicts.

In natural evolution i could imagine some species that only has a single male or female and the rest of the population is the opposite gender. Like the queen in an ants colony. Also naked mole-rats evolved something similar. The reason could be that the individuals barely produce enough sperm or eggs for the "queen" so every single one needs to contribute. As you want communists you could consider the "queen" without brain just like a reproductive tank.

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  • $\begingroup$ Thank you but unfortunately this results in a hive-based society with a limited number of reproductive individuals, which I am trying to avoid. The spawning should be structured in such a way that all the contributors are the biological parents of all the offspring spawned. That is, a given individual could have X mothers and Y fathers (or the equivalent if the species is hermaphroditic or isogamous). $\endgroup$ – Anonymous May 20 '16 at 12:42
  • $\begingroup$ suppose one could handwave that while the sperm is mixed there's some gene transfer going on. Also have everybody being fertile. My train of thought was to see the queen and drones as intermediaries for the whole colony and come up with a way that would not need such intermediaries. $\endgroup$ – bdecaf May 22 '16 at 11:38
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Since DNA is basically genes put together, you might want that every single individual which contributs has a part of this DNA in the "pool". Splitting and recombining this DNA might be the answer of your problem. Then your child will have an entire new DNA, which includes 10% parent 1 DNA, 20% parent 2, etc...

Important thing

Using DNA, as someone said before, is bound to a very specific mechanism in the reproduction cycle. It's fragile, and has a tendency to mutate easily. More parents = more mutation.

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  • $\begingroup$ This doesn't specify a mechanism. How do you match similar genetic units (i.e. chromosomes) How do you handle mismatched sequence lengths? How do you select a 'winner' from the pool of candidates? If the mechanism is too complicated, then it won't evolve, it would have to be engineered. $\endgroup$ – Monty Wild May 20 '16 at 6:53
  • $\begingroup$ @MontyWild Actually, the DNA should be a bit different in structures than our. Even if our genes are specific, the main problem is to concatenate the cut part of the DNA. The structure of the DNA would be known by the pool, which will create a structure with specifics markers and genes would "stick" to it. The faster to the spot, the winner. When the DNA is fully form, the pool would activate the reproduction cycle by secreting hormones. Note that I agree, the mechanism of multi-gametes reproduction is way too complicated to be plausible in reality. $\endgroup$ – Gautier C May 20 '16 at 7:06
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I don't remember the exact volume it was mentioned, but the Yeerks in Animorphs were a species of slugs that reproduced by having around three of their kind "combine", and then replicate into many offspring. This ultimately meant that to reproduce, three Yeerks died in the process, but it still resulted in quite a few offspring.

How this works on a cellular level isn't really clear though, and it's possible that the Yeerks are just splitting their cells up into multiple organisms, seeing as they can already do something similar with brains.

Ultimately, whatever system you use will need to produce multiple offspring with each copulation.

One idea would be that the species could lay slimy eggs all in one place. The slime around the eggs could also contain gametes that invade other eggs; however each gamete would not require a full set of chromosomes. Each eggs can decide on specific chromosomal variants to accept depending on the environmental conditions, and would ultimately end up adopting multiple gametes, picking and choosing chromosomes from each. Alternatively, there might actually be 3-5 different types of gametes that the eggs accept, which ultimately limits the offspring to just 1 "mother" and 5~ "fathers" each. (Not that the fathers would really be identifiable outside of genetic testing)

It's a complicated system, and it might actually result in a few malformed offspring every few batches, but it would achieve the desired result in the end,

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  • $\begingroup$ How about including links? $\endgroup$ – JDługosz May 22 '16 at 20:07
  • $\begingroup$ Multiple types of gametes? That might actually work. How do you suppose it would interact with the alternating generations suggestion? $\endgroup$ – Anonymous May 23 '16 at 13:18

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