With with the advancement of GMOs the idea of giving rise to humans from 2 people is possible making questions like this invalid? How many people are required to maintain genetic diversity?

With constant genome engineering to create genetic diversity on each generation of humans before conception how many generations can come from two people with ideal DNA? It is not inbreeding if the DNA is changed enough?


closed as too broad by Remi.b, canadianer, David, kmm, Muze Mar 29 '18 at 15:47

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  • $\begingroup$ all this is just speculation and I don't think we can provide you an answer on this Stack Exchange website atleast. And I don't even understand what you mean when you say "How many generations of human can come from two people"? We are all descendants of the very first individuals in the homo sapien species. $\endgroup$ – The Last Word Mar 28 '18 at 20:56
  • $\begingroup$ Also, the picture is really really not in anyway helpful for the post. $\endgroup$ – Remi.b Mar 29 '18 at 15:13
  • $\begingroup$ I think the question deserves to be close. Yet, I felt like I would attempt to give you some help. I did not down vote but I don't think this is of any importance in the discussion. I don't really understand why this is unfair. In any case, don't worry too much. I wrote bad questions and bad answers before. Sometimes I did not agree with the bad reception I got. Nobody remember those. It is the same for you, people will associate you with your best posts only. And down votes really won't affect your reputation mutation (1 point loss per down vote and you get 2 points from accepting an answer). $\endgroup$ – Remi.b Mar 29 '18 at 16:05
  • $\begingroup$ @Remi.b how can it be made better? $\endgroup$ – Muze Mar 29 '18 at 16:11
  • $\begingroup$ @Remi.b I didn't down vote either. $\endgroup$ – Muze Mar 29 '18 at 16:13

You do not need any 'editing', in theory it is possible for two people to give rise to 8 billions people. Early generations would suffer from some inbreeding depression but if you somehow get rid of it through 'editing', then you do not even have this trouble for the very first generation but you will have it for the successive generations. It is impossible to tell how important it will be and whether that will prevent this tiny population to survive though. There are ecological and sociological problems that are probably of great importance too. To make it short, it is not easy to survive alone!

For non-recombining DNA, it is necessarily true that we all currently living copies descent from a single individual (see coalescent theory although it will likely be too an advanced topic for you). This is the case of the Y chromosome (excluding the PAR) and of the mtDNA. We refer to these MRCA as Eve-mtDNA (biblical reference) and Y-MRCA, respectively.

Of course, these two individuals did not live alone, did not live together and did not live at the same time or same place. Also, none of these two individual is in anyway a good turning point for considering him/her the first individual of a new species. Y-MRCA is just the MRCA of all modern Y chromosomes and Eve-mtDNA is the MRCA of all modern mtDNA. The reality for the rest of the genome is more complex due to recombination. For your information, Y chromosome and mtDNA put together represent about $\frac{1}{50}$ of the entire genome.

I doubt this answer end up being of much help to you. You should probably just have a look at an intro course to evolutionary biology such as for example evo101.

  • $\begingroup$ No this is great. Sometimes just knowing it could be done by today's technology is great. We in theory could start over with less people then it states here. worldbuilding.stackexchange.com/questions/3/… Thanks $\endgroup$ – Muze Mar 28 '18 at 21:18
  • $\begingroup$ Never have I talked about technology in my answer. I just mean to say that there is not fundamental barrier to it. Also, I highlighted that two individuals might not be enough to ensure their own survival but it is impossible to answer this question more precisely in scientific terms because there is no way to empirically test such questions. I think you have misunderstand my answer. Also, you seem to misunderstand the scope of questions that is open to scientific enquiries. $\endgroup$ – Remi.b Mar 28 '18 at 21:29
  • $\begingroup$ I don't think we should understate the problem of inbreeding depression; sure, once the deleterious genes get selected out it would no longer be a problem, but what are the odds of the population surviving those early generations? If every couple has 20 children it's one thing, if they have two or three it's another. I also don't think we should understate the risks of that level of inbreeding to a population's survival. How many generations would it take to build the genetic diversity back to a point where the whole population doesn't get wiped out by the first epidemic? Thousands, surely? $\endgroup$ – Oosaka Mar 28 '18 at 22:10
  • $\begingroup$ 2 people could give rise to billions? $\endgroup$ – Muze Mar 29 '18 at 16:07
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    $\begingroup$ To be clear the typical pathway for speciation in real biology is not via a 2-member founding group (even if it isn't fully biologically impossible). That's a religious story only. $\endgroup$ – Bryan Krause Mar 29 '18 at 16:38

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