I'm posing this question in the terms of inbreeding depression and hybrid vigor. It probably depends on the size of the inbreeding population, and I'm making supersoldiers in a pre-industrial society, so I think I would be satisfied with 100-300 men... er, that would make 200-600 people.

It also seems to me that at a certain point it only makes sense to take in women from the general population, because only men can be soldiers (pre-industrially speaking) and they get so badass that men from the general population couldn't keep up with them in training. Does this make sense?

In other words, would taking in healthy girls for breeding be a thriving industry, or would that be a situation of "the chosen one", or a completely secluded compound, or something else entirely?

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    $\begingroup$ What, exactly, are the characteristics that you wish to breed into the supersoldiers? Bullet-resistant skin? Daggerlike fingernails? Fangs? Thirst for human blood? Conversely, what are typical human characteristics that you are willing to sacrifice? Hair? Spleens? Shoulders? $\endgroup$ – user535733 Mar 25 '17 at 20:04
  • $\begingroup$ @user535733 Um, I'm not sure how it matters for this question. I've been mostly thinking about strength, reflexes, teamwork, the stuff, but in the end I'd like each individual to be able to take down up to 100 enemies with pre-industrial weapons, so bullet-proof (or at least arrow-proof) skin is not entirely off the table. And the sacrifices can't stand out too much, because they'll have to hide among the general population in enemy-held territory. Hair and spleen are probably acceptable. :) $\endgroup$ – khantazm Mar 25 '17 at 20:17
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    $\begingroup$ Has an equivalent of Carl Linnaeus taken steps to figure out basic genetics among these people yet? Or are they kind of guessing? $\endgroup$ – user535733 Mar 25 '17 at 20:38
  • $\begingroup$ Er. Do you mean Mendel? I'm not familiar with Linnaeus' contribution to genetics. $\endgroup$ – khantazm Mar 25 '17 at 20:53
  • $\begingroup$ @user535733 With Mendel, I'm not sure how much knowledge makes sense. I think it would be more rules of thumb, than clearly formulated theory. $\endgroup$ – khantazm Mar 25 '17 at 21:23

Your question states that this eugenics endeavor is one of inbreeding, and that is the fastest way to maximize the prevalence of the traits that you want.

From http://onpasture.com/2014/10/20/breeding-matters-iii-inbreeding-vs-line-breeding/

"Interestingly, before the advent of genetic testing for recessive traits the only way to statistically ensure genetic “purity” of a bull/ram/buck etc. was to breed that bull to 35 of his own daughters concurrently. If no genetic defects show up in any of the offspring, the bull is 99.7% likely to be genetic defect free."

Your project will require a lot of incest and a lot of culling.

I found this interesting; from http://bowlingsite.mcf.com/genetics/inbreeding.html as regards all matings being brother - sister crosses:

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"The figure shows how the inbreeding coefficient chages with generations of brother-sister matings. As a general rule, this type of mating in domestic animals cannot be kept up beyond 8-10 generations, as by that time the rate of breeding success is very low. However, the rare survivors may go on to found genetically uniform populations..."

Thinking strategically you might not want to commit the entirety of your breeding population to the project because your population will crash because of inherited diseases. If there are any survivors after that crash those could be your super soldiers.

I can imagine that these super soldiers are a religious project of the society: breeding brother to sister, culling the unfit etc. The end result of your super soldier project would be that your super soldiers and their sisters / wives will be genetically identical: a stable lineage free of inherited diseases with predictable characteristics generation after generation, just like an inbred strain of lab mice.

This super soldier thing proposed here is grounded in genetics but is appropriate only for a work of fiction. The bowling site article notes that the ultimate phenotype of a stably inbred strain has a lot to do with luck and that it is very difficult to control exactly which genes these stable strains has. So the prospect of actually pulling off a breeding experiment like this in real life (human or otherwise) seems slim. If it could be done it would be a great thing for popular dog and cat breeds; the fact that these breeds still suffer from genetic diseases suggests to me it is not an easy thing.

  • $\begingroup$ Based on this, I now think I misunderstood inbreeding. I thought the concern was just about small populations, but it's more specifically about breeding siblings for a long time, and I think it clearly doesn't make sense to do it for humans, at least this supersoldier idea, because traits you'd select for are complicated and involved with nurture. The Russian tame foxes project seems like a much more reasonable model. $\endgroup$ – khantazm Mar 27 '17 at 11:13
  • $\begingroup$ I should have added to this that to select for a trait you want, you want to have that trait. If you do not have any breeding stock with bulletproof skin then inbreeding will make it less likely to occur spontaneously. $\endgroup$ – Willk Mar 27 '17 at 12:40

If you want a historical answer look to Sparta. At birth, any "imperfect" babies were tossed from a cliff. At age 7 male children were kicked out of the village and lived like animals in the outlying areas, fending for themselves, stealing, and forging bonds with older boys. At 14 they are allowed to return to society by surviving a gauntlet of the whole village beating them while they try to steal cheese, then the real training begins. It's estimated the Spartans weeded out their own men down to only the "top" 30%, or in other words only 3 in 10 boys survived to adulthood.

The ironic part is that Spartan women, while not given the same harsh treatment, do not cower from these "supermen" but instead all turned out to be ballbusters who filled in the various vacant roles in their society. Although not treated as equals, the women exercised along with the men, and ate the same meat as the men, and at least in some cases owned property, horses, businesses – this was unheard of in the rest of Greece. Although not allowed to directly compete a Spartan woman sponsored horses in the olympics. And the most flagrant display of female independence in history was by a Spartan Queen named Helen of Troy.

Any breeding program to create superior men would eventually consider the superior women that birth them (and they might actually take pride in it). Grabbing random women off the street seems to be at complete odds with eugenics, not to mention a traumatized unwilling virgin mother doesn't sound like a healthy baby factory.

I suggest more women than men in your program (at least double), with possibly a lot of brainwashing over how healthy and fit they must be to provide babies for the cause. They would be kept separate from the men, or rather the men would be kept separate from the women for reasons any farmer knows.

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    $\begingroup$ Her Spartan heritage is likely the reason of her beauty, fit people tend to be attractive. Coupled with a well fed royal diet... $\endgroup$ – Mormacil Mar 25 '17 at 20:54
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    $\begingroup$ So I assume somewhere there the hazards of inbreeding become mitigated. At which point? A population size? Or simply managing different lines? I also think I have to mention that I don't have an isolated (isolationist) city-state, but a "facility" working for the potential defense of a whole nation. I think at least there would be political pressure to introduce nobles' sons into this prestigious "caste." $\endgroup$ – khantazm Mar 25 '17 at 21:04
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    $\begingroup$ @khantazm Unless your population is completely closed off, or you are aggressively mating 1st cousins, you may not need to worry about inbreeding. In fact you will be creating "bad" breeds along with the good all the time, you will just be removing them actively along the way. Questions here about inbreeding are often about a space colony where outside genes cannot be introduced and the entire population must be preserved. Your breeding program is more like the Russian tame fox experiment where you breed for positive traits and negatives are culled from breeding: bbc.in/2cTCuks $\endgroup$ – wetcircuit Mar 25 '17 at 22:52
  • $\begingroup$ The OP asked about inbreeding depression and hybrid vigor. You answered with unsubstantiated information about ancient Sparta, which appears to be gleaned mostly from 300 via Plutarch and Herodotus (i.e. not much better than a comic book). The question was about biology, and this answer is about dubious history/sociology. I don't think it answers the question. -1 $\endgroup$ – kingledion Mar 27 '17 at 2:03
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    $\begingroup$ @wetcircuit Snark doesn't make for good or constructive replies, and we try to avoid it at Worldbuilding. If you think that there is valid biological information in a link provided in a comment, you should edit that information into your original post, so it can be judged by people who read the answers. Not everyone likes to click on links on work computers. Comments can also get deleted over time, and links can be broken, so by putting the information into the answer you can ensure that your answer stands on its own a year from now. $\endgroup$ – kingledion Mar 27 '17 at 13:21

Women determine the genetics and prenatal environment for the children--that's actually a BIGGER contribution than what the males can do. They only give 1/2 the genetics.

So, what do you do with the girl babies produced? Keep track of them. Maybe even let them back into the general population to interbreed. And then their children might have a chance to be part of the breeding program.

You can have specific requirements for the women who are allowed in--especially first generation ones.

Because it's pre-industrial, genetics won't be known. But breeding will be...so it's likely that they will track relations, and track those who score the highest on whatever scale you're rating them on. Anyone talking about genes, shouldn't be, because these folk won't have any idea what genes are--they'll just be tracking characteristics. Even Mendel, who began to understand, is actually at the dawn of the Industrial age...

The Industrial Age is a period of history that encompasses the changes in economic and social organization that began around 1760 in Great Britain and later in other countries... SOURCE

So, depending on the country, we are looking at early 1700s. By this time, we had been breeding farm stock, dogs and other domesticated animals selectively. The same can be done with humans but it take longer because we reproduce not so quickly compared to, say horses, which can be bred in three years...


What wetcircuit says. Sparta is a good example. Adding to that. You want your women to be fit. Childbirth at that technological level is dangerous. You want them to survive.

Add to that the slow reproductive speed of humans, about a year per child. You can easily have more women then men. A single one could impregnate multiple women.

It's gonna be slow though, well over a decade between birth and reproduction. I assume this will be coupled with a heavy training regime much like the Spartans?

Grabbing women from the Streets would be counter productive. You would pollute your genepool with random genes. They're untrained and you'd lose many during childbirth. Very inefficient.


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