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I'm designing a system (a computer system actually) and (a whole while ago) I spoke with a friend about it and he had this opinion:

If you combine DNA of more parents (than 2) it's better for the offspring.

It's a bit of a theoretical question but is this true?

I'm using genetic algorithms where you can choose the number of parents, if this were to be true I'd take 4 parents, if not I'd stick to 2.

I saw here a question about the occurrence in nature but it remains unanswered.

(2 parents are easier - in this system - so maybe that's the reason it is not observed in nature)

About the system: it needs to produce 'fit' offspring (as fit as possible and as fast as possible), where fitness is measurable (this part is already covered...) and the most fit individuals in the population are selected to pair.

The only limitation set on this kind of systems is that the offspring has to have a chance to be fitter than the parents (so children are allowed to be less fit than parents (being it 4 or 2).

(Of course this lowers the importance of the question but still: does offspring of more than 2 parents have a higher chance to be fit? (my friend mentioned: the more diversity in the DNA the better...))

If you need more information about this bit I'll try to answer comments (if I do know the answer or can give more information about it).

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    $\begingroup$ Ignoring the complications that S Pr mentions in their answer below, this would totally depend on the individuals involved. If you could include the DNA from a distant relative (or no relative at all) to the DNA of two siblings, you could easily eliminate the risk of inbred deleterious homozygous recessive traits. However, if just two parents are distantly related and/or would not develop an embryo with deleterious traits, then it shouldn't matter a whole lot. $\endgroup$ – theforestecologist♦ Apr 26 '19 at 2:36
  • $\begingroup$ Can you create an answer with this? (I'd upvote it), also - if you'd like - we could use you in the chat room: chat.stackexchange.com/rooms/93100/… $\endgroup$ – Bamboomy May 1 '19 at 14:08
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There are very many details to address in this question. I will try to keep it brief and keep the scope of your question in mind, which is rather narrow. I also think your friend is over-simplifying and misleading you, assuming he is honest about the explanation he gave you.

We are talking about sexual reproduction, correct? Firstly, with 3+ parents:

  • it's not obvious that you will have "more diversity" in the DNA, nor that
  • "more diverse" DNA will be a cause for increased fitness.
  • Additionally, it would take a whole lot of machinery and evolutionary happenstance at the cellular and molecular levels to recombine DNA from 3 or more parents to make a stable, recombined genome, and this itself may introduce more problems than solutions.
  • More so, you're implying that a sexual organism that requires mating between 3 or more individuals will be fitter than an organism born of fewer parents. This is subject to whether the gain in fitness of having more genetic parents will outweight the cost of maintaining such a system. This would certainly be dependent on the environment, the population, and all the nasty little details of life, such as how mate choice would work, whether a backup for 2-individual mating would exist, etc.

Remember that fitness is a probability of obtaining a number of offspring rather than the number of offspring. I think it is self-evident that the requirement for more parents, rather than less, lowers the probability (i.e. fitness).

This is quite a hypothetical discussion. In nature, for all its ever-experimenting and ever-diverging forms of life in the last 4 billion years, we find no organisms with more than 2 sexual parents. Take this as a sign that the natural occurrence of this kind of system is probably not favorable to survival and reproduction.

And I realize we could discuss this topic on many fronts (I have a few more ideas that I omit here), it's a rich question to digest.

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  • $\begingroup$ excellent answer, would you like to digest this here or do you have a place that's better suited for this kind of discussions (I have quite some remarks as well and we seem to diverge on the meaning of 'fitness', so - from my part - further digestion would be most welcome :-D $\endgroup$ – Bamboomy Apr 25 '19 at 15:30
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    $\begingroup$ If it's brief, ask here in the comments, otherwise you could make a chat room for it. I recommend making it public! $\endgroup$ – S Pr Apr 29 '19 at 10:47
  • $\begingroup$ I created a room: chat.stackexchange.com/rooms/93100/… let's digest :-D $\endgroup$ – Bamboomy May 1 '19 at 14:03

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