Architects were a rather weird civilization. You see, not only did they create servant races like demi-humans, but had also engineered themselves to be specialized in various areas. Here is the hierarchical order and their roles:

  • White:
    • White Fixer: They're effectively living archives and gods, tasked with ruling over the Architects. Their unique ability allows them to mind control those who are beneath them in the hierarchy. They have white skin with some gene-engineered marks for identification, white hair, light gray eyes, and usually a mesomorph build. They've been gone for quite a while by the time the story starts.
    • Ginger Fixer: High-grade technicians and leaders, only having to answer to their higher-ups and the White Fixers. Hair color is ginger, eye color may vary and skin tone is white.
  • Worker:
    • Yellow Worker: Lesser technicians, skin color is yellowish-white.
    • Brown Worker: Lesser physical workers for various physical tasks that are too varied for robots (gardening, for instance).
  • Black:
    • Black Troubleshooter: The tallest and heaviest sub-species, designed for combat. They're just as mentally capable as workers but have several engineered traits that make them compliant with any order their higher-ups give them, though they can voice their concerns.

If this society seems racist, that's because it is. I never said Architects were the good guys.

So, at one point, fixers had infighting, which became a civil war, which ended up unleashing nightmarish creatures, called abnormalities, on the world. The remaining White Fixers fled to a city in the sky, hidden from everyone else. Later, they disappeared from there as well, only leaving an enslaved dragon behind, who was the core of their security system.

As for the other castes, ginger fixers, and demi-humans, they've forgotten their past and formed their own societies, making use of the remnant tech from the Architects.

Of course, there is still a White Fixer left (amnesiac, of course) who is the protagonist. However, it's been so long that attempting to use his mind-control powers on humans or demi-humans would fail, even if he knew he could to that. I.e: the Architects' genetic safeguards were eroded by nature.

But how? Architects used quantum supercomputers and nanotechnology to effectively erase the boundaries of organic life. The only taboo was the creation of a Singularity, which was only done at the end of the war when there was simply no other way of stopping either the pro-killbot or the anti-killbot camps.

Simply put, Architects' chosen a method of keeping their castes' genetic code pure relied on their society existing and actively maintaining that purity. The moment the fixers were gone, the safeguards also disappeared quietly into the night.

Architect society didn't even like inter-caste relationships. When another White Fixer in the story finds out that the protagonist is dating a demi-human, she gives him the same look you'd give to a zoophile or a furry, even though demi-humans are just as intelligent as Architect Workers by default. So, if this society didn't make the safeguards more "stable" it was because they couldn't without negatively impacting the castes' functions.

They could have made so that different castes were genetically incompatible, or have the baby's caste be either the mother's or the father's with no in-betweens. So, for what "practical" reason did they decide not to do either?

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    $\begingroup$ What happen with the soma? Why throw away the soma? $\endgroup$ Commented Aug 5, 2020 at 2:09
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    $\begingroup$ @RodolfoPenteado I didn't read Brave New World, but still, nice reference. $\endgroup$ Commented Aug 5, 2020 at 2:14
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    $\begingroup$ This hierarchy is kinda racist. $\endgroup$ Commented Aug 5, 2020 at 2:27
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    $\begingroup$ @Renan "If this society seems racist, that's because it is. I never said Architects were the good guys." $\endgroup$ Commented Aug 5, 2020 at 2:30
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    $\begingroup$ Does this siite really need questions about nazi wet dream society questions described neutrally as as "rather weird" as hot network questions? $\endgroup$
    – Yakk
    Commented Aug 5, 2020 at 14:40

7 Answers 7


Because of exactly what happened:

Your society could control reproduction by social means, so making them incompatible was unnecessary. But these folks were REALLY smart, and anticipated the possibility of everything falling apart.

Specialization is great for a rigid, stratified and predictable situation, like civilization. Many species are perfectly adapted to a small, narrow niche they control perfectly. But specialization is a problem when conditions change. Specialists go extinct. Even if your society was obsessed with purity, it recognized the danger to humanity if everything fell apart. They probably even saw it coming.

Your masterminds predicted their own apocalypse and made sure that the genes could mix and de-specialize humanity when it was needed. It's exactly the intellectual preparedness you would expect from a bunch of eugenic geniuses. After all, generalists would be the optimally adapted species.


Those artificial alterations were result of evolutionary pressure regardless of being intentional - being part of a certain caste favored having a corresponding gene since all soldiers were guaranteed to have the black gene as opposed to the white gene. Once the said civilization dissolved, the evolutionary pressure maintained by the elite disappeared. Color genes had no pressure that favored them anymore, and over time those genes were lost due to mutations, interbreeding without any pales shaming people for it, other forms of genetic drift etc.

As for why the architects decided not to make the castes unable to interbreed, it was too costly for no benefit. Giving everyone one gene or two is hard enough not causing a whole cascade of genome failures. Eliminating genetic compatibility would require either way more dramatic genetic alterations for something they could accomplish through guaranteed and much cheaper social means


Aftermarket mods.

Sex is sloppy! Heritable traits are a nightmare from a stability perspective. You need serious inbreeding and regular culls, and your precious trait could vanish without warning from the regular process just from the mechanics of meiosis.

Better to engineer the normal base organism after conception. Huxley's Brave New World accomplished this by manipulation the circumstances of artificial gestation.
Current CAR-T tech offers a platform to jump off.

This is awesome stuff. Genetically engineered supersoldier T cells, taken from the organism, genetically modified to fight cancer, then put back in. CAR-T are warrior cells but you could do this with a whole range of different cells, differentiated and not. The dream of CAR-T cells is to have an off-the-shelf cell type suitable for lots of different people, sidestepping the time and expense of custom CAR-T for each patient. That is what your society had - standardize post-conception organismal mods. This also allows flexibility - instead of breeding a new line, just tweak your mods. Adult organisms could also get these mods as is done with the CAR-T cells.

Once the tech to introduce these genetic mods are gone, organisms who are conceived just remain the basal type.

  • $\begingroup$ So, combining this with Chebi's answer, if the creation of new White Fixers is heavily regulated by their own caste, the moment they disappear, so does the possibility of new White Fixers as the procedure that creates them can only be carried out after the approval of the others. Lesser castes, on the other hand, are required in larger numbers, and classical reproduction can still keep useful traits while being cheaper and the safeguards are regularly administered anyway. $\endgroup$ Commented Aug 5, 2020 at 18:17

To find the system violators

No system is perfect, obviously, so when you make a caste system and strictly forbid any romantic liaisons between the various castes, it doesn't take a genius to figure out what's going to happen. Sure, using safeguards (such as say, secret police) you can have a 99% success rate keeping them apart, but tragic and forbidden romance seems to be an unfortunate subset of the human condition. In other words, the Architects knew that people would violate the rules.

The Architects response was to make the offspring of such a match a very clear hybrid - deliberately - so that it was as obvious as possible that the child was from a mixed-caste couple, thus implicating the child's parents, or mother at the very least, though the father shouldn't be that difficult to find in most cases. A term for these mixed-castes might be something along the lines of 'the Architects judgement' or something of that nature.


It was simply too much work, and it would interfere with engineering potential new castes in the future, or at least make it more difficult.

After all, their society was perfect. It would never fall. Why go to the bother to make life more difficult for yourself?


You may not have large enough populations at the top to maintain enough genetic diversity only among the ruler classes.

White fixers: They're effectively living archives and gods

I don't think you'll have many of these running around. Make it so they can only reproduce among themselves and you have a tiny gene pool at your disposal. Also, do these walking gods even care about reproduction enough? I'd guess there would be a lot of test tube babies around. That way taking genetic material from other castes isn't as big of a issue as if it required direct contact. Then you jsut need to nanobot that embrio in the direction you want it to develop, maybe making it's white inherited genes more active or maybe not even that.

Maybe all the white only traits are close to 100% nanobot induced. So you don't even care about the genetic expression of the baby or if it takes more to the white parent or to the other caste one. You jsut input the baby's dna into the computer and call it a 'white baby' from now on the nanobots will recognize it as such, make it's hair white (even more so than it would have been) and give it all the features a prper White Fixer should have.

There's probably some protection to prevent babies without a white parent to being allowed in the system so white fixers are always needed.

Now, these explains why not go with the genetic incompatibility route. So, why not make the babies one caste or the other, with no inbetweens?

First, I'm not a genetic expert, but I'm not sure how you could do this without the nanobots assistance. But for the sake of the argument let's assume it's possible. Well, the issue here is, it makes it too easy for rogue caste members to get more high caste members on their side.

What I mean is, say you have a white fixer who wants to gain power but doesn't have the support of other white fixers. He can easily get more white fixers to support him by mating with other castes and waiting for the offspring to be white. Remember, having a small population of white fixers ensures you need some chance that interbreeding produces white fixers. This expliot is averted if all new white fixers need to be explicitly allowed and accepted into the system.

This makes a lot of sense if you ask me, since if you think about a white fixer, all their power means you can't just have them poping up without control. It'd be as letting a general have as large of an army as he wants or a politicial as much votes in the senates as he chooses.

Now, a counter argument to that would be to not let all white fixers have the same ammount of power. Meaining to have a hierarchy within them. So many white fixers wouldn't give you more control of the army, since they aren't General White Fixers, same for since you'd need Politician White Fixers. But the think is, there still needs to be power in the general white fixer population, maybe to elect the Politicians or somthing else. Otherwise, the core societal value that one's caste give you power and makes you fit to rule comes crashing down.


You don't need to worry about anything, the genetic separations between castes are going to naturally vanish anyway when the civilization collapses without any special explanation

This is something you see in feral animals all the time. Humans have bred domestic animals for centuries for very specific characteristics. Then these animals accidentally get released into the wild, and within a few generations they end up reverting to the wild type as the carefully maintained separation between bloodlines break down and genes that code for traits that work well in captivity but are terrible outside of a system where every animal is bred for a certain job are selected against and die off. Some examples include...

  • Razorbacks are feral pigs in the United States descended from what anyone would consider normal pigs: pink, sparse hair, no tusks, etc. Razorbacks now are almost indistinguishable from Eurasian wild boar, and reverted to that form within a few generations.
  • Dogs, when released into the wild, will rapidly return to a wolf-like state as the scattered "wolfy" alleles in the gene pool get selected for. Dingos are a good example of this. The only evidence that domestication ever took place is that feral dogs tend to be a bit friendlier and more tolerant of human handling than true wild wolves and can more easily be redomesticated.
  • Goldfish are released into the wild all the time by ignorant fish-owners. What happens is after a few generations all the weird breeds like bubble-eyes and butterfly tails die off and the goldfish rapidly revert to a form that's pretty hard to tell apart from a plain old carp.
  • Similar things have been documented in horses, goats, sheep, cattle, chickens, and numerous other domestic animals. And some plants too, believe it or not.

What's going to happen in your situation is that people are going to start interbreeding between castes due to lack of suitable mating partners due to whatever apocalypse causes your civilization and its social structure to collapse, and the averaging is going to produce something pretty similar to the humans your civilization's eugenicists started with. Extreme alleles that worked well in the caste system won't work well in a hunter-gatherer survival situation and will get selected out of the gene pool over generations.

Now, as to why the genetic engineers didn't just make all the castes sterile if they intermarry, that's a plot problem, not necessarily a worldbuilding one. There's really no reason for the fixers not to do it if they are as bigoted as you describe, and ideologues of that magnitude don't really care if humanity would be wiped out if their ideology gets proven wrong. These people are crazy racist ideologues with a quantum supercomputer that can manipulate genetics like a god, they don't seem the type to be very practical or reasonable. However, even if the fixers did genetically engineer all of the castes to be unable to interbreed, you are going to get a few mutant individuals for whom the genetic blocking mechanisms are defunct, and it is going to be these individuals in a post-apocalyptic scenario who are going to be the ancestors of most of future humanity due to same-caste mates being at a premium and these mutant individuals being the only ones who can reliably breed.


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