If aliens came down to Earth and enslaved humanity, how long would it take to selectively breed the humans to make them more docile and less resistant to their alien captors? For example, if they just bred the most friendly and least aggressive humans, killing off the rebellious ones, how long would it take to make the humans domesticated, much like the way dogs and cats are?

The aliens in this world are extremely long lived; the average lifespan is about 1,000-1,500 human years. The aliens' government is roughly based on imperial Rome. They invade other species' planets and either assimilate or kill and enslave them. Keeping slaves is not necessary to them as they have advanced artificial intelligence; keeping slaves is seen as a symbol of wealth and power, with only the elite owning slaves.

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    $\begingroup$ How long would it take to invent money? $\endgroup$ – Hot Licks Dec 11 '17 at 23:46
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    $\begingroup$ I am curious at to why you ask that ? Am I missing something? $\endgroup$ – Mawg says reinstate Monica Dec 12 '17 at 9:44
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    $\begingroup$ In both asking and answering this question, one might want to contemplate whether (and how much if so) modern human civilization has been already creating selective pressures in favor of more "domesticated" humans for thousands of years. $\endgroup$ – mtraceur Dec 13 '17 at 18:22
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    $\begingroup$ @Mawg At the risk of strawmaning Hot Lick's position due to comment length limit, Hot Lick is probably making the implication that money (or perhaps more specifically capitalism as a society-wide system) turns otherwise normal humans towards behavior that we would consider domesticated. It's a position some people hold and certainly worth seriously contemplating, though I myself consider it to be a flawed/incomplete perspective on how humans work. $\endgroup$ – mtraceur Dec 13 '17 at 18:27
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    $\begingroup$ IC IC. Well, to have any sort of society where people interact with each other, it's going to be very difficult to avoid barter, and that will, almost inevitably, lead to money. I can't see how it can be avoided, although I do understand the point about what it leads to. $\endgroup$ – Mawg says reinstate Monica Dec 14 '17 at 7:14

11 Answers 11


As previously stated humans could be very easily trained if taken from a very young age. On top of that any genetic influences could also probably be bred out within 10-20 generations.

Experiments have been conducted with Silver foxes breeding the most aggressive and the most docile of each generation producing remarkably different temperaments as can be seen here.

Similar experiments have also been conducted with rats with similar results. There is no reason to believe that humans would be any different.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Dec 14 '17 at 3:52
  • $\begingroup$ I haven't read all of the answers here, but I assume that such an advanced alien life form would also be able to directly manipulate genes. They could even selectively breed different looking humans artificially (if they don't cooperate) the way we have such a variety of different looking dogs and cats. $\endgroup$ – Jack R. Woods May 27 '18 at 15:12

One doesn't need to selectively breed humans for selecting character features. Education can go a long way, as it was proven by the Romans: take the children of the aristocracy of a conquered people and raise them as Romans, then send them home. (credits @Will for the italic text)

Just take babies from their parents and grow them up to have good relationships with the alien masters. It will take 10-15 years, and the aliens will have friendly humans available, without the hassle of breeding them.

Once the first generation has been raised, they can very well keep up the job almost on their own.

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    $\begingroup$ This was a favorite maneuver of the Romans: take the children of the aristocracy of a conquered people and raise them as Romans, then send them home. $\endgroup$ – Willk Dec 10 '17 at 15:05
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    $\begingroup$ This answer, even though quickly accepted, is missing the important distinction between domestication and taming. $\endgroup$ – pipe Dec 10 '17 at 18:25
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    $\begingroup$ Yes and no. You can get a sufficient portion of the populace to support you - but it all depends on how well you can support the belief system you instil by your deeds. Some will be fanatic enough to discount any wrongdoing by the glorious aliens but many will secretly resist if the aliens truly treat humans as slaves. It may take a few generations to get to a level of indoctrination that has you been revered as gods. In most Soviet block countries there was a good level of resistance and once the power grip loosened the whole system fell apart. $\endgroup$ – Frank Hopkins Dec 10 '17 at 20:14
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    $\begingroup$ @Will "take the children of the aristocracy of a conquered people and raise them as Romans, then send them home." Which taught the more independent minded former hostages (like Arminius) how to beat the Romans. $\endgroup$ – RonJohn Dec 11 '17 at 1:05
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    $\begingroup$ I can't agree with the initial statement about kids reporting their parents/relatives for anti-revolutionary behavior. As someone who lived through some of that and whose parents/grandparents lived through all of it this just wasn't something that happened normally. You would get the usual familial infighting, but that had nothing to do with education. In other words if someone reported a family member 99 times of a 100 the reason was they wanted them out of the way rather than feeling beholden to the state in any way. $\endgroup$ – DRF Dec 11 '17 at 6:48

Williams syndrome

If they only want a few hundred thousand they might have all they need right away.

There's a rare human disorder, Williams syndrome.

Williams Syndrome is a rare condition (1/10,000 births) caused by the deletion of some genes on chromosome 7.

When somebody checked which gene was most different in dogs versus wolves, and they found it was WBSCR17. The WBS in the name stands for “Williams-Beuren Syndrome” because the human version of the gene has been linked to the disorder.

People with Williams Syndromes have short noses (compare to the short snout on domesticated foxes), smaller teeth (compare to smaller teeth in dogs vs. wolves), smaller brains etc

People with Williams Syndrome are friendly, chatty and pathologically trusting. Many have learning difficulties but some have a fairly normal IQ, it doesn't help. They're still pathologically trusting, as in they can barely conceive of someone not having the best possible intentions for them. There's been some reports that williams syndrome children are basically incapable of racism among other things. They tend to get abused/molested at a much higher rate than the general population.

Williams syndrome phenotype

If aliens arrived on earth and wanted to domesticate humans they could find an estimated 20,000 to 30,000 people in the United States alone already with williams syndrome. Probably a few hundred thousand from all around the world.

There's various other health problems associated with the syndrome but selecting the healthiest individuals with near-normal IQ they could probably simply start a breeding program including a large fraction of Williams syndrome individuals and quickly (decades) have plenty of humans almost entirely incapable of believing that their alien masters have anything but the best intentions for them.

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    $\begingroup$ +1 because, although all the answers are fairly good, this one focuses mainly in selecting genes which make the domesticated species, well, domesticated. Brilliant answer. $\endgroup$ – tfrascaroli Dec 12 '17 at 10:29
  • $\begingroup$ The problem with picking such extreme mutations is viability of the population. $\endgroup$ – Konrad Rudolph Dec 12 '17 at 10:58
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    $\begingroup$ @T.Sar Many modern dog breeds are of extremely poor health due to excessive breeding. ;-) Propagating a single, neurodegenerative trait through the whole population has a good chance of destroying it. And, again (see other comments): humans are not dogs. Extrapolating these things without explanatory model is hard. $\endgroup$ – Konrad Rudolph Dec 12 '17 at 12:26
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    $\begingroup$ @KonradRudolph That is true, but that works for the intended purpose (pets/human companions). Pugs obviously can't survive on the wild for long, but they have a bigger population than several animals, like tigers, for the sole reason that we take care of them. That is my point about caretakers - the population isn't left by itself, it is actively maintened by an external force. $\endgroup$ – T. Sar Dec 12 '17 at 13:48
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    $\begingroup$ @Xen2050 to be fair, the question was about domesticating humans which is smack bang in the middle of the definition of eugenics, and not even the ok eugenics like people choosing tall athletic partners to have kids with or the grey-area eugenics like people choosing traits for their own children. This is pure darkside litterally-treating-humans-like-dogs eugenics. $\endgroup$ – Murphy Dec 13 '17 at 10:57

Biologically, humans are already domesticated. The theory is that we actually domesticated ourselves when we developed agriculture. The concept still has some controversy, but most of the arguments for human self-domestication stem from osteological analogies between the bones of ancient vs. modern humans, compared to those of other domesticated animals. For example, a serious injury in a modern human would not have been as serious for an ancient human, due to their bones actually being thicker.

So an extraterrestrial species would not need to "domesticate" humans, unless they have their own definitions of what an intelligent domesticated species should be like (which is likely, if they are practicing slavery). Either way, I do not think any amount of genetic engineering will completely eliminate slave revolts. Most likely some kind of drugs or hormonal control would be needed, but the best option I think is simply through cultural change, like others have suggested here: kill all the parents and then create a new culture with the children.

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    $\begingroup$ Welcome to WorldBuilding Nicole! I see that you are a new user. On this site we prefer more elaborate answers. That might be the reason for the downvote you received. Could you please edit this answer and expand it a bit? For example: is there a source you could cite that would underline your statement? If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! $\endgroup$ – Sec SE - clear Monica's name Dec 10 '17 at 22:08
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    $\begingroup$ In fact there's a great article about how humans were domesticated by wheat, and not the other way around.. $\endgroup$ – JeffUK Dec 10 '17 at 22:11
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    $\begingroup$ Admittedly, the idea that humans domesticated themselves is still controversial. Most of the arguments stem from osteological analogies between the bones of ancient vs. modern humans, compared to those of other domesticated animals. For example, a serious injury in a modern human would not have been as serious for an ancient human, due to their bones actually being thicker. I did do a quick Google Search, but couldn't find any reliable academic citations. I read about the theory a long time ago, and would have to do some research or go to the library to provide any reliable sources. $\endgroup$ – Nicole Sharp Dec 10 '17 at 22:15
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    $\begingroup$ We have a tag that would require citation from books and academic articles. That would be the hard-science tag. This question does not have that tag, so you don't have to go to such lengths for an answer. Is there maybe a Wikipedia article that would outline that discussion? Otherwise it would already improve your post if you could edit the discussion points from the comments into your post and just explain why you would assume that we domesticated ourselves. $\endgroup$ – Sec SE - clear Monica's name Dec 10 '17 at 22:24

The question really comes down to what the slaves would be doing.

Bear in mind that many people already do fairly tedious jobs in return for a reasonable standard of living for themselves and their family. Historically (and still in many parts of the world) those jobs have often been dangerous. Even so, people have done those jobs because they didn't have a good alternative choice. Unless slavery is more dangerous than, say, mining in the 1700s, I don't see a massive drive to rebel. If slaves do not have particularly harsh duties and are basically just set tasks to keep their owners amused - playing music, sports, or whatever - then it's almost impossible to see them rebelling, and hence "domestication" is unnecessary. Hell, anyone who tries opposing the aliens is likely to be lynched by their fellow humans who quite enjoy their comfortable lives.

This also makes me question why the aliens would bother to kill humans. They have AI, so robots can simply move troublemakers to internment camps.

If the aliens are not kind masters though, some type of domestication will be necessary. It does not necessarily need to be bred in, of course. The aliens in The Tripods used brain implants to keep their human slaves under control.

I'm afraid this is a bit of a standard B-movie trope. See Slave Race, or Turned Against Their Masters when some humans fight back later (as in The Tripods). You're going to have to do something rather special with this concept if you want to keep suspension of disbelief, otherwise you're likely to end up with just another 30s/40s pulp sci-fi pastiche.

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    $\begingroup$ Please, always post a warning when posting links to tv tropes. $\endgroup$ – Anketam Dec 11 '17 at 20:41
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    $\begingroup$ @Anketam Any particular reason? The ads can be annoying, sure, but it's not NSFW. And some pages may be unsuitable for young children, but we don't need every answer on SE to be kid-friendly. And you're perfectly free to hover over the link to find where it's going, and if you don't like TVTropes then you don't have to click on the link. Unless you can bring up a specific requirement on SE for the TVTropes site to specifically have a warning attached, then basically, nope. $\endgroup$ – Graham Dec 12 '17 at 11:55
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    $\begingroup$ I apologize if it came of as being serious. There are people who when click on tv tropes links end up losing hours of their time. As such it is considered nice to warn people, so that those who have not built up a tolerance to tv tropes do not end up getting lost on a wiki walk. $\endgroup$ – Anketam Dec 12 '17 at 15:36
  • $\begingroup$ @Anketam No worries. Irony is the reason smilies were invented. ;) $\endgroup$ – Graham Dec 12 '17 at 15:53

I'll take a contrarian approach. It will take less than 30 years to domesticate humans.

The invading aliens are technologically superior to such an extent that their technology is like magic to us.

If they can travel interstellar distances, they have us beat in that same way that dogs cannot understand how our household technology works. The dry food arrives in either a paper or plastic bag. The wet food arrives in tin cans (not that they understand paper, plastic or tin). Humans cause the food to come out of the containers like magic. Water is always in the toilet, ready to drink.

So the alien overlords have AI, unknowable materials science, near instantaneous surveillance and superior weaponry. Resistance is futile.

Human science, engineering, and most learning will collapse because there is no point studying Einstein if he's just been proven wrong and we don't have the intermediate steps to get to whatever the aliens understand of physics. Again dogs can't understand refrigerators let along jet aircraft.

Religious conservatives, the military, nationalists, the wealthy, elites and politicians will be killed during the invasion. Any survivors will commit suicide unable to understand the world they find themselves in.

The human population will probably shrink by a least a billion, probably by 90%, possibly by 99%. That leaves 70 Million humans. Still probably too many if the Alien elite need only trophy humans for the status symbol. They probably only need a breeding population of 50,000 to 100,000 humans. The aliens could take the long view and allow humans to continue living in cities without culling the population.

If the aliens allow human culture to continue, are generous with food, medical attention and shelter, there should be a flowering of human creative endeavours as humans have nothing else to do but create art, books, music, movies, theatre and entertainment. Bread and circuses.

Humans will be left with art and sex as their only pastimes. By the time the children born on invasion day reach puberty (say 12-15) any "old-timers" notions of human resistance will have vanished. By the time those children's children hit puberty they'll be like the Eloi in HG Well's Time Machine. Life will be idyllic, simple and totally dependant on the mercy and good treatment of the alien overlords

As a result of comments I note that "Einstein being proven wrong" is inaccurate in the same way that Einstein did not prove Newton wrong. However, Einstein did state that nothing can travel faster than the speed of light. So the aliens are either:

  1. Interstellar travellers with warp/hyperspace/whatever FTL ships
  2. Generation or Suspended animation ships travelling interstellar distances at slower than lightspeed
  3. Interplanetary aliens that we cannot detect either from the outer solar system or cloaked in the inner solar system.

All 3 scenarios significantly exceed our technology. And the most likely scenario is they've cracked FTL travel.

They've also invaded and enslaved humanity. So the starting assumption is they kicked our asses.

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    $\begingroup$ You're taking a lot of creative liberties, the question doesn't say anything about technological superiority, no "magic" or materials or surveillance, or disproving Einstein... maybe they just have impenetrable suits of armor & hit people with sticks. Maybe the just stay in orbit & throw down the occasional rock to destroy a few blocks when things get out of line... $\endgroup$ – Xen2050 Dec 12 '17 at 17:20
  • $\begingroup$ Actually the question does make all of those creative liberties logical. Alien invasion of Earth means they are not from earth. So by definition technologically superior and sufficiently so that we don't win. All my "creative liberties" are merely the most obvious disadvantages. We have a shot at being superior in human medicine and that's about it. It's worse than Europeans invading the Americans. We lose if they want to colonise rather than assist us. Actually "disprove Einstein" is inaccurate in that Einstein didn't "disprove Newton" $\endgroup$ – paulzag Dec 14 '17 at 1:39
  • $\begingroup$ Not necessarily, there's a really fun story about 1500's tech level "space pirates" that somehow found out a really simple way to travel through space, but they fight with muskets & cutlasses... you can guess what happens to them & their "empires" when they try attacking machine gun wielding, fighter jet equipped, nuclear capable Earth. (And you said "no point in studying Einstein if he's just been proven wrong"...? Edit required?) $\endgroup$ – Xen2050 Dec 14 '17 at 18:14
  • $\begingroup$ Centuries after countries have been annexed, the inhabitants will often attempt to gain independence, even if there's no reason to think that life would be better if they got it. 12 or 15 years is not going to make people forget about the time before the aliens arrived and there are plenty of people who will resent them and their presence, simply because the aliens can't trace their ancestry to some minor torp in south western wales in the 13th century. Einstein may be wrong, but that doesn't mean he's irrelevant. People will still study his works. $\endgroup$ – Clearer Jan 2 '18 at 21:06

I think the official dictionary definition is a good answer on it's own.

"to tame (an animal), especially by generations of breeding, to live in close association with human beings as a pet or work animal and usually creating a dependency so that the animal loses its ability to live in the wild."

Especially the latter part about creating a dependency. This could be done in different ways. One way would be as the series "V" did. Come to earth and "give" technology away. In the long term people will become depended of the technology.

You could also tie it in with out current climate problems. These problems are created by the aliens. Slowly destroying our atmosphere, only to swoop in and save earth. Off course making us completely depended to them. After a 1000 years (Not really that long for the aliens) it will be the status quo for us humans, maybe we will even see them as our gods we need to obey.

In short you first need to create obedience and after a lot of (human) generations make this the normal state of affairs. This however does not mean some humans will not bite if cornered. The time span will obviously depend heavily on the how you do it. It could take generations for the aliens or be instantly if you use some sort of brainwashing (As in the latest UFO computer game). Also the line between the humans being forced slaves and being domesticated is pretty gray for a while.


As intelligent and inquisitive creatures are conceived as a threat, the aliens might be unwilling to reveal to humans anything about their past. They might separate the adults from their children (as said earlier) and raise the children in a new society, letting them meet only with like-members.

Part of the "domestication" process is controllig such information and creating the impression that humans and the aliens always lived side by side while humans lacked any notion of culture and technology. They might do that for every few genarations, if they realize humans became too inquisitive and are suspecting that there is more than meets the eye. For instance: humans would inquire where the aliens bring the food from, and why can't they get it by themselves? Why humans are confined to particular places unlike the free-roaing aliens? Why that human was reprimended for somethig he has done, and what wron did he do? There are numerous events in which humans would communicate and attempt at starting a rebel, and the aliens must keep an eye on.


I'd say if you want adult specimens asap with an explosive collar you would have enough to make them obey ofc you would have to blow 1 or 2 just to make an example.

If you want fresh from baby stages it would take 1-2 generations remember our education is what makes most of our personalities if you teach them from little that defiance = pain they will obey willingly.

To truly domesticate like you would do with an cow ... i believe it would be nearly impossible but this depends mostly how the aliens are (as a race) be it the most advanced goat in the universe ... if power runs out in the super goat-battle suit tonight we are going to eat goat soup (an example of an animal race going full alien).

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    $\begingroup$ Seeing others punished isn't the best deterrent of behaviour. If it were, no one would commit crimes today, but they still do. A dog's shock collar would probably be much more effective than just blowing up a few people's heads. $\endgroup$ – Xen2050 Dec 12 '17 at 17:25
  • $\begingroup$ I'm pretty sure that education has very little influence on our personalities; despite having very different lives, my grandfather (whom I only met three times in my life), a carpenter and fireman and I, a computer scientist, have very similar personalities. My daughter (5 years old) is a virtual copy of my mother (no formal education to speak of) in terms of personality. My wife (about to complete her masters in African studies) reminds me of her father (only had 7 years of basic school) way too much. Please provide a source on that claim. $\endgroup$ – Clearer Jan 2 '18 at 21:15

As with any sort of livestock the results are not so much based on how they bred so much as which offspring are culled and which are chosen to breed new.

Another aspect that is important is how they are trained and educated. The more they are taught to think creatively, and act independently the more likely they are to rebel. Think of the dog that acts out when it doesn't get its way. The difference here is that humans have far more developed brains than dogs or other livestock. They can learn new things, and be creative. These are traits that complicate domestication.

If humans are treated as Equals or even just given free access to information and communication with others, some will eventually develop a desire to rebel, and fight back. However if information and learning is limited and controlled, normal brain development can be retarded and the ability to effectively coordinate can be diminished. Humans are not the most dangerous and top predator in the world because we are strong, but rather because we are smart and have access to tools that we can leverage to make us stronger. If you eliminate that ability to learn to work together effectively, you remove a big portion of the human race's strength.

That said, how effective of a slave or pet would you have if you retard development of the ability to think, reason, and coordinate? Imagine if humans were reduced back to the basic abilities of the severely mentally challenged. Any race of alien that has the ability to do this, would likely be able to produce robotic type constructs that could handle any task far more effectively and with less error than a mentally hobbled human could.

More likely the race is advanced enough to modify the human genome to reduce the incidence of independence, violence, and any other traits that the master race finds troublesome. But still I would expect that there would be some serious need to cull the herd pretty regularly to keep a properly restrained herd.


One look at slavery in the past will tell you humans have an inbred desire for freedom and thus will never be domesticated which is another word for slavery.

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    $\begingroup$ While your intent is clear, your premise is unfortunately provably wrong. If your claim was true, then there never would have been slavery, or generational slavery - and there would be no slavery today. 10 seconds on google tells me that there's between 21 and 30 million people living in slavery today. $\endgroup$ – pbeentje Dec 11 '17 at 7:56
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    $\begingroup$ One could argue that as of today, some 80-90% of the population of western countries are slaves to capitalims. They could stop cooperating, but unless they resort to stealing or begging they had next to no chance of survival. $\endgroup$ – Burki Dec 11 '17 at 9:06
  • $\begingroup$ I think the word "inbred" is the wrong choice of wording. Perhaps Inherent or instinctive or Intrinsic $\endgroup$ – Chad Dec 12 '17 at 20:11

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