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I'd like to know how many people it would take to begin a genetically stable civilization. I don't need/don't care about the infrastructure aspect, only the genetics. Scenario-wise let's assume there are two continents, a large one to the North and a smaller to the South. For a long time (maybe a thousand or so years) there have been many people living on the upper continent, but none on the Southern one. Something happens that causes some people to sail across to the Southern continent (war, cataclysm, prophecy of cataclysm, etc.). They all settle together in their new home. For some reason nobody else from the Northern continent comes at any point in the future. We're also assuming that they're from about five different regions on the Northern continent, and, either because they're opposed to the idea of selection or because they left in some haste, that they're somewhat randomly selected. Considering the fact that some of them would die (let's assume 15%), how many people would it take for them to start (and continue) a civilization with a low rate of genetic disease?

Mocascoolai
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  • Depends on how lucky they are, doesn't it? If they are fantastically extremely lucky, one man and one woman will be enough. If they are just extremely lucky, five men and ten women would be enough. If they are simply very very lucky, twenty men and forty women will be enough. If they are only very lucky etc. etc. When you did your diligent research, what did Google say about a mimimum viable population? – AlexP Oct 05 '23 at 23:21
  • see the 50/500 rule:https://www.britannica.com/science/minimum-viable-population – KEY_ABRADE Oct 05 '23 at 23:35
  • @KerrAvon2055, the question you referenced deals with a sci-fi scenario, which means technology my world wouldn't have. The answers to said question were, however, helpful in finding a rough estimate, which was all I really needed. Thanks! – Mocascoolai Oct 06 '23 at 00:06
  • How many people are required for a healthy re-population of the Earth (Post-Apocalypse)? – Mazura Oct 06 '23 at 00:58
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    I see the point @Mazura is making, but I think what you're asking is, what's the smallest group of people that can procreate without a significant divergence from normal hereditary/genetic problems? The problem with that question is that the consequences of interbreeding aren't as linear as you might think and some consequences are worse than others. If you're willing to put up with it (and assuming sizable families), you could start with 2 people. Or you might need thousands of genetically disparate people. If you can't explain where the line is (how bad is bad?) we can't reasonably answer. – JBH Oct 06 '23 at 02:05
  • 2? No, it's like 5k. "4169 individuals (95% CI = 3577–5129)." https://en.wikipedia.org/wiki/Minimum_viable_population Surely though between those two questions this has been beaten to death enough. Not that it matters : "There is no unique definition of what constitutes a sufficient population for the continuation of a species, because whether a species survives will depend to some extent on random events. Thus, any calculation of a minimum viable population (MVP) will depend on the population projection model used." – Mazura Oct 06 '23 at 02:11
  • @Mazura Worse, we've had plenty of questions about the minimum necessary to ensure the success of a colony, too. Mocascoolai, is there a question beyond genetic minimum and colonial minimum? – JBH Oct 06 '23 at 02:23
  • @Mazura You know, based on the OP's response to Kerr citing that Q as sufficient to answer his/her question, I have to agree to close as a duplicate. – JBH Oct 06 '23 at 02:57
  • It's only my opinion, but I think, mammals at least, can bring the colony from one man and dozens of women quite quickly. The more females the faster growth. At one generation he could have hundreds of offspring. While there'd be another, similar situation on other continent, the next generation can be paired adequately, and go into thousands, tens of thousands in just 2 gens. It's lucky scenario. The farther generations lowers the genetic infringements, but in so many years the geopolitics may change at your world. – Peter.k Oct 20 '23 at 10:36

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