I recently watched the classic film Gattaca, which is about a world in which humans are selected with desirable traits at birth. Ignore all the ethics of abortion and genocide (like those claimed for Iceland). I can not help but notice that human biological variation will take a big toll and the presence of mutations in the population would become virtually non-existent because they almost always are initially a disadvantage (until adverse environments are formed).

Any species will be able to survive for maybe a century or so, but with the course of time there will inevitably be an event in which the current "desirable" traits would not thrive. In fact, this could lead the race to extinction because common mutations that could enable the species to survive may be lost.

These technologies are present in the world right now, and technology to design new genes was neither shown in the movie nor is present in the current world. Superior children are chosen based on the genes of the parents only (in the real world, we also use genes from other sources). Whether or not it is indeed possible to design new genes is out of scope of worldbuilding I think, so I have left that out as a grey area.

My first question is whether I am over-exaggerating the issue? Second, if not, what can the society do to manage the growing trend to survive in such a potential future?

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    $\begingroup$ Dogs seem to be doing pretty well, and we've been choosing their best traits for thousands of years. $\endgroup$
    – Giter
    Jun 18, 2018 at 19:19
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    $\begingroup$ @Giter Sure they're doing well now, but what happens if humanity goes extinct? Without humans, breeds like Sausage Dogs and Pugs can't survive in the wild. Just throw a Pomeranian into the Jungle for proof. $\endgroup$ Jun 19, 2018 at 0:09
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    $\begingroup$ @Sydney Sleeper: Perhaps some breeds can't survive, but that's because the people who breed them select for what wins dog shows. Most working breeds would survive quite well, IMHO. Or for an actual example, consider horses. They were selectively bred by Eurasian humans for thousands of years, then some were imported to America (and Australia), some escaped from domestication, returned to the wild, and have survived quite well. $\endgroup$
    – jamesqf
    Jun 19, 2018 at 6:12
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    $\begingroup$ What's to prevent the people in charge of designing this program from including a carefully considered degree of variety? "Breeding" programs for food crops are designed to give farmers options based on environmental changes. We could do the same with our human breeding program. $\endgroup$
    – dwizum
    Jun 19, 2018 at 12:45
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    $\begingroup$ @SydneySleeper There are a lot of animals that wouldn't survive being thrown into a Jungle. For example, an octopus would have a hard time climbing trees and breathing air for extended periods. Generally dogs don't live in jungles. If you released that pomeranian into fields and woodlands it might fare better. $\endgroup$
    – Pharap
    Jun 20, 2018 at 7:59

7 Answers 7


Yes, species can survive eugenics. Many already have (though admittedly not sapient species). Every single species ever domesticated by humans such as cows, dogs, cats, bees, pigs, chickens, llamas, horses, sheep and innumerate plant species have undergone 'eugenics'. Humans have selectively bred these species for millennia, and they have not died out yet.

It is true that negative health impacts have been seen in some of these species. For instance, the banana is now incredibly vulnerable to pathogens, the pug can't breathe properly, and the chicken has a lot of problems pumping out so many eggs. These creatures have not been driven to extinction, mainly due to the fact that the decrease they experience in biodiversity is made up for by the increase in numbers from being artificiality spread across the world (something that is not a problem for sapient species that are extremely effective at proliferating across the worlds they inhabit).

Is it possible for eugenics to cause irreparable damage to a species genetics? Yes, but only if done ineptly. For example, I point you to sixteenth century European monarchs whose obsession with intermarrying and royal purity caused major inbreeding and ultimately led to the downfall of many royal lines.

That being said a semi-competent but nonetheless evil state wouldn't need to worry. Worst case scenario you just slightly irradiate sperm before use to introduce additional mutations into the gene-pool.

That being said, just because something probably won't wipe out humanity doesn't mean it should be done.

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    $\begingroup$ It's also worth mentioning that some of those domesticated species can survive pretty well in a feral state as well. (e.g. cats, dogs, pigs, horses, to name but a few) So, for some species, not only have they not died out, but they haven't lost the ability to survive in the wild, either. $\endgroup$ Jun 18, 2018 at 23:08
  • $\begingroup$ If anything, I would see that as a counterexample. No, pugs won't survive if humans suddenly disappear. $\endgroup$
    – ndnenkov
    Jun 19, 2018 at 6:10
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    $\begingroup$ Even domesticated chickens can become feral. Just so long as they aren't the truly prolific egg layers or meat producing varieties found on factory farms. $\endgroup$
    – Dan Clarke
    Jun 19, 2018 at 8:12
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    $\begingroup$ Small wording point: in the first paragraph, I guess you mean “sapient”, not “sentient”. (“Sentient” = “capable of consciousness/feeling”, so most animals and certainly all mammals are generally considered sentient; “sapient” = approximately “capable of intelligence/knowledge”, and is typically reserved for just humans or the most intelligent animals, cf. Homo sapiens.) $\endgroup$ Jun 19, 2018 at 12:56
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    $\begingroup$ as far as the inbred royals go, the ability to edit genes to correct for the buildup of such harmful mutations eliminates the risk from inbreeding. You could take one man, use his X doubled to create a woman, and make what is essentially a clone species - no harm for perpetual interbreeding when you can clip out the harmful mutations. Comparatively the aristocracy would have excessive diversity. The only downside is having a similar immune system leaving them more vulnerable to a single contagion, but competent healthcare takes care of that. $\endgroup$ Jun 19, 2018 at 21:10

You are seeing diversity as a safety net; when the whatever comes that kills 99% for sure we won't be certain what made that 1% special ahead of time or we would have seen to it it wasn't only 1%. But if a great purge never comes it isn't certainly important.

Eugenics looks at genetics like wealth; if we have stockpiled enough advantages when Bad Things happen we will get through it using those advantages. Or like maintaining any other code; finding and removing bugs during good times means bad times are both rarer and less painful.

A eugenics plan thought out well enough to be repeated sober isn't likely to kill a species by itself. Even breeding for hemophilia or cancer vulnerability wouldn't certainly be doom. Because to get to the point of considering eugenics you have to have brain power and strong social cohesion.

Intelligence and social cohesion are very powerful traits that can conceivably cover any biological limitations; a million years ago who would have bet on the apes? The story goes that some of the oldest writing in the world is complaints about people being less tough than they used to be, but quality and quantity of life pretty consistently improves on average by any standard. Modern medicine especially antibiotics, hygiene and vaccinations do not contribute to our genetic fitness, but vastly reduce the threat of Bad Things.

Further homogenization isn't a certain outcome for eugenics. It takes many generations to achieve any breeding results, humans have pretty long generations and there are many different conceivable goals so it could make sense to run multiple lines in parallel. Certainly if it is considered on a species level you have the population to do so.

  • $\begingroup$ I don't see homogenization to even be likely - people have different preferences about what should be emphasized and what trade-offs are worthwhile (and fashion changes too quickly). $\endgroup$ Jun 19, 2018 at 21:14
  • $\begingroup$ @pluckedkiwi I think you are mixing the difficulty with getting people to like eugenics with the ability of a project to proceed. The most famous attempt involved an autocrat who was hoping for a 1000 year continuity. Several other multi-(human)generational science projects have followed pretty closely the original plan. $\endgroup$
    – user25818
    Jun 19, 2018 at 21:41

I'm not a professional geneticist, but what I do know about the topic is that every change isn't a net gain or loss; it's a tradeoff.

Some of us (for example) metabolise excess energy intake from food into fat. This is a great trait for areas where food is scarce and lets us build up reserves when larger food supplies are available. Where it falls down is in areas or times of plenty, where the increased fat reserves actually hinder survival should the Bad Things happen.

Some of us metabolise excess energy as heat; great for cold environments, not so great in the tropics. Yet others metabolise it as muscle. Quite rare, but it allows for increased strength for (say) areas where the principal food source is predation.

The point being; what we consider to be 'good' or 'bad' largely depends on our environment at the time, and it's that change in environment which essentially is the Bad Thing that causes us so many problems.

One of the things that has made humans so successful has been our generalisation; we can eat a much wider range of food than most animals, can use our limbs to do a wider range of things than most animals, and where the environment is still hostile to us, we have learned to adapt the environment and ourselves to suit.

Think fire, clothes, agriculture, etc.

It's that ability to adapt and work from a generalist base that affords us the most protection from the Bad Things in our future and as a general rule, eugenics is often described as a form of specialisation. It'll make us smarter, stronger, etc. Only thing is, there is no such thing as 'stronger', there is only a tradeoff between fast twitch, total muscle strength, stamina, etc. In other words, you can be more agile, have more endurance, but not both (beyond some basic general improvements). Same goes with strength and flexibility; you can't be specialised in both.

You can burn off excess food as heat, OR you can store it as fat. You can't do both. The first means that you can eat (almost) as much as you want and not gain weight. The second means that you can eat far less and still be comfortable. Which is the better trait for survival? But, which is the one everyone wants?

Ultimately, eugenics can tune the human body to be better overall only to a point; after which, specialisation is the only way to improve specific traits, and that always comes with a cost. Eugenics may not destroy a populace, but ultimately it may make it harder for people to survive with specialisations that the Bad Thing makes undesireable for some reason.


I agree with the top answer that dogs are a perfect example of long term eugenically selective breeding, without them dying out (though you could argue that the average small dog is less equipped to survive in the wild now).

However, it seems you're conflating a few things.

mutations in the population would become virtually non-existent

Mutations are an exception to genetics. In most cases, picking a certain set of genes from either parent will give you a guaranteed outcome. Dominant and recessive genes are a basic example here.
Mutations, however, change the expeted outcome. They are unforeseen and happen randomly. Mutations will occur regardless of whether you handpicked the genes (eugenics) or shufffled them randomly (biological reproduction).

The only way to prevent mutations from occurring would be to alter the biology of actual "baby generation" (I can't find a better name for it). Most eugenics I've heard of (including fictional) generally revolves around picking the desired genes but still letting nature take care of the actual "baby generation" process.

because they almost always are initially a disadvantage (until adverse environments are formed)

Adverse environments are not formed because of existing mutations. Mutations do not occur because of adverse environments. These two things are separate and coincidental.

A mutation which coincidentally happens to solve a problem, will enable the mutated animal to have a better chance at surviving an adverse environment, thus allowing the animal to reproduce more and generally spread its mutated genes around.

Disclaimer: My answer focuses on practicality, not ethics. I'm not personally advocating eugenics.

My first question is whether I am over-exaggerating the issue?

Referring back to what I said before; I think so. Mutations will still occur. There are three possible outcomes:

  • Positive mutations have a habit of sticking around. This applies to nature (more reproduction, either through increased survivability or mate selection) and eugenics (more people choosing the mutated gene)
  • Neutral mutations will generally mean that there's no discernible drawback or benefit, which means it slips by unnoticed (e.g. the color of your stomach lining - no one cares). The odds of the mutation persisting is effectively random chance.
  • Negative mutations have a habit of being weeded out. This applies to nature (less reproduction, either through decreased survivability or mate selection) and eugenics (choosing to avoid the mutated gene).

Putting ethical issues aside, eugenics are really just speeding up natural selection. Arguably, being free to choose your mate is selective eugenics. Which means that pretty much every animal engages in eugenics. By selecting the right mate, they are somehow able to maximize the (still somewhat randomized) genetic outcome of their offspring.

Natural selection is a slow, brute-forced process, but it usually ends up consistently improving a species.

Eugenic selection can be incredibly fast and can bypass the brute-forcing stage because intelligent decisions can be made. However, this does open the door to making intellectual mistakes that negatively impact a species.

Two examples of this, one fictional and one real:

  • Jurassic World. An dinosaur is eugenically bred to be the most amazing killer, to amaze visitors. And then it outwits the zoo keepers and escapes.
  • Killer bees. Created during research. Not intended to be let out of the lab. Then they escaped.

Second, if not, what can the society do to manage the growing trend to survive in such a potential future?

I'm not sure what you're asking here. Regardless of whether a baby's genes are hand-picked (artificial) or randomly shuffled (biological), the baby counts as one life.

Are you assuming that eugenics will increase the amount of babies that everyone has? That eugenics will nefariously implement a "planned obsolescence" in cheap eugenic options?

These are interesting things to explore, but your question as asked doesn't really explore this. What do you mean by the growing trend to survive in such a potential future?
If anything, you'd expect gene choices (for eugenics) to be made specifically to improve on the otherwise randomized gene selection. If eugenically created babies were somehow more defective than their biological counterparts, there'd be no reason to chose eugenics over the natural way.

  • $\begingroup$ just one tiny note, right before your disclaimer you can generalize "animal" to "organism" because it applies to all life, not just animals $\endgroup$
    – V. Sim
    Jun 20, 2018 at 2:07

My first question is whether I am over-exaggerating the issue?


First, unless there was widespread genocide, different societies and different families are going to have different opinions on optimal genetics. No one wants Down syndrome &c. or poor cholesterol handling &c. but (a) those mistakes don't make up the majority of the genetic code and (b) it boggles the mind to think of any change to our natural environment that would make them adaptive. If your society is expecting parents to have any bond or connection that prompts them to love and raise children (rather than handling them all through central caretaking, which current human development wouldn't handle well at all), then it's going to have to leave most of mom and dad's DNA and simply remove problems; it won't be able to give people clones of the ruling class and expect them to be at all cared for.

Second, mutations occur as a natural part of cellular reproduction. We'd presumably keep track of the code at birth, but living beneath the sun produces its own edits, as do a host of other human behaviors. If anything, being able to restore genetic code (i.e., cure cancer) would permit people to indulge in more risky behavior than at present.

Third, if a massive environmental change (e.g. nuclear winter) occurred that made most humans' genetic code maladaptive (e.g. too little vitamin D and too poor endurance in low-temperature environments), the level of tech that you're describing would presumably allow CRISPR and other tech to 'patch' not only fetuses but many or most of the existing population.

Second, if not, what can the society do to manage the growing trend to survive in such a potential future?

The only maladaptive changes are likely to be

  • Cosmetic. With complete control of the genetic code you'll have many people—in East and South Asia if not Europe and the Americas—wanting lighter skin that provides less protection against solar radiation. It's not really an issue since there's sunblock and, as mentioned, the potential ability to 'reset' cancer produced by this vector.

  • Gendered. Some traditional societies prefer male children to female, which can skew the population in unpleasant ways. It usually works itself out—societies advanced enough to deploy this tech en masse typically value women—but places where it doesn't may require government intervention. That happens, as do societal changes like Chinese weddings now being paid by grooms, who are expected to provide gifts, a house, and a car, which makes having girls more advantageous for a family.

  • Metabolic. On a personal level, it may seem fun to eat without gaining weight while increasing everyone's height and lean muscle mass. On a societal level, it's obviously problematic if everyone's caloric intake bumped up by a factor of two or even to Ryan Phelps levels. Even with present-day tech, though, that's not insoluble. It just means we'd need to spend a lot more of our income on food, esp. proteins, until lab-made meat caught on. Esoteric foodyism would have to go by the wayside except for the overclasses. So, unpleasant tradeoffs, but survivable and probably worth it.

The only real epidemic risk of genetic modification is new tailor-made diseases; their threat would be real, since they could target some of the universally employed adaptive changes, but they'd be just as simple to fix via CRISPR &c. once scientists could identify the genes or proteins being targeted. It'd just be much more essential to avoid total wars or permit access to the offensive/defensive part of the tech by private individuals, similar to how nuclear power is treated now.


There are in general three condition that can make a species die out.

  1. Competition. A more fit species crowds them out.
  2. Their only food source dies out.
  3. A new predator or disease arrives from somewhere else. They/It cannot be a locally evolved since the prey would then have evolved right along with it.

In some cases local diseases can push a species over the edge, but only if they are already threatened by one of the big three. Otherwise there will always be some survivors that can bounce back and repopulate.

Now look at humanity:

  1. Humanity has no competition. Not even close.
  2. We make our own food. We eat many different foods. If another Potato Plague arrives, we might run low on food, but we will never run out.
  3. There is no "somewhere else" anymore. Unless you add aliens.

So, mankind is basically in a very good shape to handle crises of almost any sort.

We are also pretty smart, which gives us a huge toolbox to handle otherwise serious problems. Medical science is utterly amazing already and will only get better in the future.

Gattaca style genetic selection will narrow our gene pool. This will make us more susceptible to diseases and parasites. BUT: Our other advantages means we can shrug off the consequences.

Or so I believe.

One problem I see with Gattaca as a future is that they are selecting against mental illness, which probably means they are also selecting against creativity. Expect stagnation.


On Earth, from the perspective of climate change, if eugenics resulted in a net reduction of the population, then it could actually improve our long term survival. I say this on the basis that if eugenics significantly narrows the range of people who were permitted to breed, that might diminish the size of our population, which would then diminish deforestation and consumption of fossil fuels, which would slow down the speed that animal species go extinct, which could lead to the food web staying intact instead of collapsing.

I should point out that, on a related note, the human species is one of the species most resilient to extinction on the entire planet. The only real threat to our survival is to destroy our habitat and the food web. For instance, it's been claimed that if bees went extinct, the human species would go extinct as well within four years (because pollination is vital to our food supply, breathable air, mitigating the greenhouse effect, mitigation of soil erosion, and the way in which plants provided food supply for all other animals). We could very well be one of the last macroscopic species that is still standing, but if everything below us goes, so too will we go. If other animal species can be preserved, we will be preserved. I know this sounds unrelated, but loss of a livable habitat is one of the only near-term extinction threats that our extraordinarily adaptable species can't overcome. Our population has been continuously burgeoning, and disease has failed to slow it down. In fact, the global population is currently about 16.5 times as high as it was just before the black plague. The original question assumes that conventional evolutionary pressures could wipe us out, and they could, but on the whole, we are much more resilient than that.

But anyways, off the tangent and back to the main discussion. Provided that eugenics is informed by health science and not racism or vanity; we should be selecting to weed out genetic diseases, weak immune systems, autoimmune disorders, etc. If that were the case, we would already have a substantially improved mortality rate and greater survival in the face of a potential extinction event (presumably a pandemic plague). Remember: some diseases like influenza have higher kill rates among the already unhealthy and immune compromised; so as you select for stronger immune systems, less autoimmune disease, less asthma, etc., you have fewer people dying from these potential contagions. But as you see with the Cavendish banana, all members of this cultivar are essentially clones, and thus they are very vulnerable to global extinction (which the previously popular Gros Michel cultivar already experienced). Any sort of eugenics program should ensure a degree of genetic diversity and immune system diversity. Instead of totally removing a lot of the population from the breeding pool, you should be screening their individual reproductive cells for cells which don't contain deleterious traits, and allowing conception with their healthy reproductive cells, if possible.


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