# How to avoid evolution for a language made to be spoken across an entire galaxy?

In the SF book I am trying to write, the galaxy has been seeded with human life by (not so much) benevolent AIs. Despite isolation between the worlds, everyone speak a single universal language made by the AIs themselves. I am trying to figure out how this language could stay the same across an entire galaxy millennia after the seeding. My current explanation is that the AIs made the language an evolutionary dead-end with little to change without the influence of an other language. How could a language be made an evolutionary dead-end or at least very hard to modify?

The AIs disappeared the moment the seeding was complete and except for a relatively small "civilised space" and its peripheries, most human worlds are totally isolated from one and another.

The AIs seeded each worlds with "vat-babies" as there were no original human left. They left "nurse" robots who taught them how to form a rudimentary society and the AI language, making it at one point truly universal. My goal was to make it stay universal at the moment of the setting despite isolation between human societies (~2000 years after the seeding)

• What is an "evolutionary dead end"? Dec 12, 2021 at 14:31
• By evolutionary dead end I meant impossible to change. A language that would always stay the same without the influence of another dialect. Dec 12, 2021 at 16:02
• Only dead languages are unchanging. Anybody who has learned Latin in the last twenty centuries can read the works of Cicero and Caesar and Seneca, because the language is dead and, being dead, cannot change. You cannot have at the same time a language alive (that is, being transmitted from mothers to their children) and unchanging; but you can easily have one or more widely known dead and unchanging languages, such as Greek, Latin or Sanskrit in our world. There are literally millions and millions of people in this world who know one or more dead languages; it's perfectly normal and natural. Dec 12, 2021 at 18:01
• We can't even do that now on one puny little planet. Go back just one millennium, and most people wouldn't understand any language spoken on Earth, even the precursor(s) to whatever language(s) they're currently fluent in, unless they've spent a good deal of time studying ancient languages. Dec 13, 2021 at 17:04
• Even Latin is not "dead enough". There are ~1M people (Catholic priests) using it on a daily basis in their work. Dec 14, 2021 at 7:34

# People continually make up slang and new language.

You can't make a language an evolutionary dead end, people can just make up new words, pronounce stuff differently, and do as they wish.

# The AI left a bunch of toys for everyone which only respond to said language.

The AI didn't want to see their colonies destroyed, so they left a bunch of artifacts which have various useful local properties- weather prediction, battle modelling, production of exceptional tools, stuff like that. They all have language AIs in them which have a very fixed language. Dominant cultures always have a few of these, and will speak the language the AI gave them because they want to use these artifacts.

• Thank you for the reply. I mostly wanted to make two peoples from each side of the galaxy able to understand each other. It is a big part of the plot/lore that most remnants of the AI are located in a library on a single planet whose inhabitant have the role to spread technology among the star (Mostly to encourage the formation of a single great interstellar empire as part of their plan). Another part of the lore is the cult toward those AIs spread during the seeding, I wanted to make this language something holy but I thought it would only make it the sole language of a religious elite. Dec 12, 2021 at 15:29
• If you want the language to stay constant, then there needs to be a constant reminder of the language to keep it pure. If you want the library to have most of the higher tech, and the cult to be fairly constant, you could have most AI remnants just not give people technology. Dec 12, 2021 at 17:42
• Indeed, I think I will scrap the idea of everyone speaking the same language but each world, culture and ethnicity speaking a variation of the language while the closer you are of the library, the "purest" form you speak. Dec 12, 2021 at 18:41
• And the language split into two, ‘High’, the language of the gods, and a multitude of ‘low’ variants. Dec 13, 2021 at 9:32
• @Joe Exactly. The AI language will be what Sanskrit is in India, or Latin was in Europe's Middle Ages. Dec 14, 2021 at 3:11

Kill the AI language.

People learn their local language and the galactic AI language. They don't use the AI language in everyday life, only for formal communications. So, like how scientists use Latin terms to prevent meaning drift, bureaucrats across the galaxy can still communicate in the AI language even if they can't talk to one another in their daily life language.

• Or Standard Arabic? Dec 14, 2021 at 16:30
• There's historical evidence that classical Sumerian was retained for hundreds of years as a prestige, "dead" language of scholarship after the majority of the population had shifted to Semitic languages. Similarly, classical Greek, Biblical Hebrew, Old Church Slavonic, and Elizabethan English (used in the 1611 King James Bible and learned by many modern-day English-speaking Christian Protestants for use in worship) could qualify as "dead" languages still in use. Dec 15, 2021 at 12:23

English is not my first language, so I find easier to talk to other non native speakers because we tend to use a "standard" version with no slang (unless the slang becomes widely known, which only can be because native speakers use it). So my proposal would be:

## The language is for very special ocasions only, no one speaks it natively.

### Because of Religion

It is a second language that everybody must learn because is used by God, so it is perfect as it is and cannot be modified: there is no valid slang when talking to God, a very formal usage is requiered so no evolution is allowed (like Latin was used by the Catholic Church as the only valid Bible's translation).

### Because of Technology

"Nurse robots" are still present to take care of the humans and they only speak this language. You must learn it to communicate with them as they are the source of upper knowledge. You need their approval to be considered an adult citizen and this includes a test using the formal language. Machines do no evolve so you only can use their language exactly as they do.

• Exactly this was what I wanted to answer. A living, spoken language evolves. But a somewhat foreign, always formally taught language that nobody but ambassadors, teachers and foreign communicators actually use, that is overwhelmingly taught from books (or pre-recorded / AI genereated media), won't evolve (much). And even if it does in a few circles of hobbyists, it won't affect the broader population Dec 13, 2021 at 12:53
• Ditto. Look at how Latin has clung to life due to early Bibles being written in it. Actually, in the old world, latin was the "galactic" (well linga franca of Europe) language. Maybe that's why Latin is so complicated - AI's could easily handle six cases. Hang on... how did the pyramids get built? Dec 14, 2021 at 5:44
• @Bohemian Point of order: six cases isn't a very large number. Finnish has fifteen! Dec 14, 2021 at 16:53
• @Bohemian - The Vulgate Bible is but one book written in Latin, and is probably not the reason Latin "hung around". As you said, it was the lingua franca of educated and less educated peoples; thousands of books (e.g. books of prayer, herbal medicine books, poety, literature, etc.) were written in Latin. Homer's Odyssey was translated into in Latin >200 years BC. I'm pretty sure Latin would still be studied today even if there was no Bible. Isaac Newton and Descartes wrote in Latin. The Vatican helped, sure, but it's not the major reason. Dec 15, 2021 at 8:44

Absolute Control Over Education

The only way to prevent a new language from spawning would be to actively prevent anyone from creating a new one. The AI must have absolute control over all education systems and learning tools in these worlds.

Rather than having schools that are run by biological teachers, it would make sense for the AI to have schools that are run completely by the robots that it makes. These teacher robots would be made to only operate with the language the AI programmed them to work with and thus only teach the one.

Every species in every world would be taught the same set of letters and the same set of pronunciations, and they would constantly be tested on it to make sure that they adhere to a certain set of parameters. The AI would program the machines to prevent branching dialects to the best of their ability, so it would chastise the students if they ever attempted to write a different set of symbols, or pronounced the words any differently than how they were intended to be spoken.

To ensure that this remains the dominant language, the robots would constantly test people on their proficiency with the language. Anyone who excels at the language and these tests will be granted a high place in society. Anyone who does not excel at the language will be pushed lower. While there are many other things they could be tested on, proper language usage is imperative to getting a good score. Because the people in power speak the universal dialect and only that, they will actively prevent other languages from developing. After all, a new language might undermine their power.

It would also be important to have a precise dictionary with clear and unquestioning pronunciations. There is only one right way to say everything, so even the slightest deviation from the spoken or written form will be noted by the robots and deemed unacceptable.

This does not really fit too well with what I would call a "benevolent" AI, but it would be the strongest way to prevent branches in the language. If this is the only way anyone has ever known for countless years, and any deviation is met with intense scorn both by society and the robots that help govern the world, no one would dare to set up a new language. The younger you mold the future generations, the less likely they will be to turn against the old ways. Once they have accepted that this is just "the way things are done" it will be very hard to turn them away from the language.

Imagine how much more vindicated they would feel about their language being the only right one when they go to other planets and find that even alien species speak it too.

Mechanical Attachments

If you want to take it even further, make the robots even harsher about how they run the education system.

Perhaps everyone has a computer chip installed in their brain along with other mechanical attachments. If you get the spelling of a word wrong or the pronunciation wrong, it will autocorrect it until the person finally gets it exactly how the computer wants it. Failure to do so will result in a serious headache. Repeated failure will increase the pain until they are finally willing to do it the "right" way.

There might be another attachment around the mouth or throat to prevent accents from forming. If it was a collar, for example, words only come out of the device when a person speaks rather than their mouth. It would ensure that the dialogue that reaches other people's ears is always the exact same every single time. There are never any fluctuations in tone, even between people.

Whether its intentions are good or not, the only way to allow a forever unchanging language would be for the AI to systematically prevent new ones from ever forming.

To Summarize

All species have to communicate using special collars, even among themselves to prevent new accents from forming. Writing would be replaced with typing to prevent deviations in how the letters are made. Education would start from an early age to press that this is the only way the world works. People who excel at the language get high places in society, and those who do not get low places.

Finally, there would be a reward and punishment system. Conformity to the standards set by the AI equals no pain and high reward. Deviation from the AI's will equals pain or the revocation of privileges. The harshness of the system depends on your decisions as an author, of course, but even the nicest AI would need to act like a strict parent for this system to work.

It would teach them that its way of communicating is the only way to communicate.

Edit: If the robots have all vanished by the time that the main story starts, then that makes my answer a little more complicated. I still think an advanced AI would be able to leave enough technology behind to have most of these amenities intact. If not, then I still think installing computer chips and handing out language-controlling collars are still solid ideas.

Indoctrination and education are still the way to go, but they would have to be deeply ingrained in the people. Before they eventually give out, the machines would tirelessly make sure to teach the species that this is how things are done and to never stray from the path.

It would be like the establishment of a pseudo-religion. The robots indoctrinate people to conform, and the biological teachers do so. Parents teach children, children teach the grandchildren, and so on to infinity.

Indoctrination would need to be significantly harsher to work without any robots enforcing it. The people would need to be incredibly fervent in their conviction to never change it, to the point of obsession. Dictionaries would essentially become religious texts to them.

• Thank you for the reply. Don't worry, the AI (in fact there is a few of them) are not benevolent, just doing there job and they don't really like it. The problem is that, at the moment of the setting, they are gone. In fact, they mysteriously disappeared after the seeding, only leaving warden to ensure mankind build primitive civilisation before they also shut down. I should have specified that in my question but I love your idea Dec 12, 2021 at 15:59
• This is the only correct answer. You can't stop drift but if AI runs the education systems, the drift can be continually pruned out. New words and meaning will happen but won't be taught to the next generation so die out. If the AI no longer exists, the language drift will continue. Dec 13, 2021 at 4:49
• I don't think that's enough, think dialects - everyone can speak the official language and it is the tested one and whatnot, yet it takes less than 50 km in any direction to find dialects I struggle to understand (when spoken fast among each other) even though they use most of the same words. Dec 13, 2021 at 10:18
• Note that this only works with an absolute control over the people, and doesn't require absolute control over education. Language is learned through living and listening, not through studying in a classroom. In fact, one needs exactly 0 schooling to become fully fluent in a language. What's more important (and the only necessary step) for our AI is outlawing words and dialect variations, similar to George Orwell's 1984. Dec 13, 2021 at 16:06

You could have it encoded in a religion which the AI creates for the people. Islam has successfully kept Arabic very close to the same for many centuries now. This creates a cultural reason for education to be founded in that religion, and also creates a later factor for if you want the people to revolt against the AI.

• This is the way to go. You will have evolution in language, but as long as the religious language is preserved and unchanged, it will remain known. There was vulgar Latin spoken by the people, and classical Latin used in religious context. Same for Arabic, the spoken versions vary a lot but the version in the Quran is intact and still understandable. Also, everyone can learn the classical version of the AI language as part of their study. And how cool would it be to meet another civilization and to be able to speak with them in your Sacred Language? Dec 13, 2021 at 9:18
• Islam has kept Arabic unchanged exactly as the Catholic Church has kept Latin unchanged; that is, both languages are dead and unchangeable. Of course, only those Frenchmen or Italians who put in the effort to learn Latin actually understand it, and only those Algerians or Moroccans or Iraqis who put in the effort to learn Quranic Arabic understand it. (What is true is that Arab countries use a semi-artificial language called Modern Standard Arabic as their official language; but then a sort-of Latin was used as the official language in various European countries for quite a long time.) Dec 13, 2021 at 13:35
• Same with Hebrew and Latin. Dec 14, 2021 at 3:14
• @AlexP : "a sort-of Latin was used as the official language in various European countries" so much so that for example in Hungary Latin remained the official language well into the 19th century, despite not being the native language of anyone in the country! (I only included this because most might think that Latin was used for diplomacy only in the Middle Ages)
– vsz
Dec 14, 2021 at 21:06
• Elizabethan English (the language of the 1611 King James translation of the Bible as well as Shakespeare) is very much alive among English-speaking Protestant Christians and is even used for composing new materials. This is arguably an especially interesting case as it is not a fully "dead" language yet due to remaining mutual intelligibility with 21st century English. I have witnessed diglossic shifting myself - people will go from speaking ordinary 21st century English and then suddenly start praying "We pray unto thee, O God, who art the mighty God, that thou wouldst grant unto us...." Dec 15, 2021 at 12:30

Today, we are witnessing a standardization of language around the globe. The way this is happening is through rapid communication between everybody. Slangs and dialects arise because of communication barriers that prevent a new word from propagating to others.

It is impossible to stop a language from changing with new words and new phrases because people always encounter new situations and new generations invent new words to describe what they are learning.

So, to keep language the same across the universe, you need to have a rapid (faster than light) communications system accessible to everyone. You also need the AI to be able to learn new words.

• Thank you for the reply, the problem is that most human civilisations are quite isolated from one of another and most don't have FTL (only those in what I call "civilised space" and its periphery which is not that big in comparison with the greater galaxy). Reading all your answer, I think I will go with the idea that the more you are away from the center of this "civilised space" the more the "universal language" is "corrupted", giving the "civilised people" a feeling of superiority over the barbarians of the periphery. Dec 12, 2021 at 15:40
• "We are witnessing a standardization of language around the globe": no we do not. Mandarin Chinese and Parisian French are not converging in any meaningul way. Even assuming the charitable interpretation that you are speaking about English specifically, we are not seeing a convergence of the different major forms of English. Quite the contrary, the distance between them is increasing. Dec 13, 2021 at 1:43
• Slangs often exist to create intentional barriers. Dec 13, 2021 at 5:15
• @AlexP Actually, those two languages demonstrate my point. Both are standardizing wide sections of the globe that used to speak many different languages. Many times, today those different languages are called "dialects". Dec 13, 2021 at 21:45
• Another to view "impossible to stop a language from changing with new words and new phrases because people always encounter new situations" is in reverse: if the language already has an expression for every possible concept, then it will be stable. Dec 14, 2021 at 16:35

an interesting topic...

I think, languages change based on several intentions. So you have to prevent all of them.

• simplification. If something is difficult to speak, or too slow, it will be reduced or combined or even replaced). First the speech is changed but at some point, it will also conquer the written forms

• creativity. Some people like to create new words or combinations, just as fun, but sometimes based on other goals, e.g. as someone said, to separate a group from others (like a secret language)

• meaning. If new things or contents appear and they are used frequently enough you want a new word for them

• restrictions. Sometimes you need to adapt language to technical restrictions (like Morse code, SMS) or sometimes even to intentional created restrictions (Twitter)

• expression. Cultural changes might create a demand for new words or even grammatical changes. Words can be forbidden in some way (or declared to be "bad" word) or there is a change in behavior (think of sexual revolution)

Evolution follows evolutionary pressure, so it might be most appealing to force a language in some way to stay constant.

Some of the points above can be channeled into a parallel language like a local dialect, or even a totally different language.

E.g. in Germany we have an official language, which happens to be the dialect of a single region where some aristocrats lived.

People usually speak their regional dialect but fall back to the official language when writing. The official language is defined by a committee and is taught in school. This ensures everyone knows the official language without restricting most of their daily life. Some professions like journalists strictly follow those rules, in part because it's commercially more successful, when more people can understand your writings, e.g. newspapers can be sold globally.

So, the official language makes it easy to communicate globally and the local language fits other demands.

Simplification can be a design goal for the standard language. The committee (or here the AI) can regularly check which simplifications people use and integrate that into the standard. But the demand for such changes is low, if everything is simple from the beginning.

Creativity is maintained by the local language and very popular words can be added to the Standard.

Meaning can also be added to the standard if necessary. New global meanings must usually be communicated globally too.

Restrictions could be put upon global communication to force a shorter and simpler language.

Expression is also maintained by the local language. Only a few words or phrases will be added to the standard, to express new cultural meanings.

As someone already said, it should be useful to establish a desire to communicate in the standard language. This could be a global broadcast (like TV or news services or movies which are mostly in offical language), or services that can only be requested by using the standard language. If the language is simple it will spread and gain acceptance (think of English vs. French, Spanish, Portuguese, all had a good start position given their colonies, but English is simpler, so it became a defacto standard in the internet).

I'd use a lingua franca controlled by an AI to keep it updated. But you must know that a language evolves very quickly if used. (roughly ten years for young people) It is not a problem per se, and the people using Dutch can understand German with a bit of effort. The same goes for Spanish and Italian. If people are far from each other, realism dictates the language will diverge.

It doesn't seem very difficult. Just have a look at how many dialects disappeared after the spread of radio and television taught to everybody the national language. Look at how widespread English has become with the help of pop songs and the internet. In the same way a widespread mass media system is killing language diversity it could kill evolution. Let people develop their own slang. But control the language used on the media. Generation after generation the mainstream language will be learned and re-learned while the slangs will fade out replaced by new ones.

Recording Technology

The ability to record the sound of language (eg. through TV, audio recordings and the like) could, speculatively, slow down the rate at which language changes with time. In the real world I think we haven't had said technologies long enough to know for certain yet.

For example:

"Oh, I remember this cartoon my child is watching. Its the one where the red blob talks about things that are red. [looks up cartoon], Oh wow! Its 2,000 years old! My great$$^5$$-grandparents probably watched the same thing!"

I think that (at least to me) this is far more plausible that an "evolutionary dead end".

Kind of a frame challenge, but...

## You can't prevent different people to modify their language to their needs

Even on a same country you have different instances of a language, either due to local culture, environment, or many other factors.

## What you really need is a "language framework"

Instead, your AI taughts very specific and strict rules to follow, togheter with very clear reasons of why each word is what it is. So, when any civilization or group of people comes with a new word, they'll follow such rules and, as the rules and bases are the same across the galaxy, other world's civilizations will be able to understand such word by dissecting it down to the base rules.

## Genetic encoding

I suppose I should say something more than just the heading, though I think it pretty much speaks for itself (no pun intended). There is a "divine" (or however you want to describe it) language that is encoded into the DNA of seeded races. Left to their own devices, a seeded being will always tend to develop this language naturally; if taught another primary language instead, this language will always be intuitively understood even if never before used. This will cause the language in use to resist long-term changes and, in the event that long-term changes do happen anyway, the primary intent of a foreign speaker will be understood intuitively. This also has the benefit of being able to handwave much of the actual implementation.

Languages are ever-changing even the ones that are most constant in the world. Although some words across many languages have sounds that resemble those spoken by prehistoric humans, all of them have evolved. To imagine that human kind had been seeded over a universe without changing languages is impossible because there would be dialects on planets. Consider that the more isolation that occurs between human groups the more the language dialects evolve as separate branches of a tree. If human kind lived in an interplanetary society where it was difficult to reach each other, language and culture would splinter and develop remotely.

Also, imagine how many new words humans would develop if they arrived on planets with new continents, seasons, flora and fauna. There would be an endless supply of new vocabulary.

Even high levels of human group interaction cause languages to shift. Consider English, it is a lingua franca language of trade, but through the evolution of English it has accepted and stolen "loan words" from many other languages, so that old English is now unintelligible. I admit there are some restraining forces: dictionaries, language teachers, and various societies that enforce specific grammar. While these forces do hold back change to an extent, so far they have failed to prevent new words from being coined and added to those same dictionaries, and teaching traditions.

If an intelligent AI ruled the universe, it would probably ensure that communication could occur, and it might develop the most used language, but chances are the innovation would be technological rather than some aberration in the way that languages evolve. Unfortunately the idea of a communicator is so much more plausible than a universal language. You hardly need to write SF to theorize about the existence of a communicator, because we are approaching one now with Google translate, text to speech, and speech to text. Tech is a more likely solution.

Language always changes. There's no way to keep the language people speak day-to-day static, that's just not how people work and would be instantly unbelievable.

However, if your AI language were the equivalent of Latin in the Middle Ages, you have a good chance at semi-stability, i.e. change would be there, but at glacial speed.

The core idea is to have this be a dead language (i.e. nobody speaks it as a native speaker) that is used to communicate between many, many people that all speak different languages and rarely ever meet. In other words: The humans who use it need to keep it stable, or their ability to communicate with remote other humans breaks down.

Second pillar: Make the language used for religious purposes, where tradition, scripture, etc. forces it to be unchanging. You can't just change the words of the Lord's Prayer, after all.

• Nobody speaks 'basic' on their own planet, +1. If they do it was colonised. Dec 17, 2021 at 13:36

Nanotech Autocorrect.

The AIs initial control of human reproduction allowed them to make sure that no human could be born whose brain would not be altered by nanotechnology making it impossible for them to express themselves in language using any means but the original language.

Since new words can no longer be created, one side effect of this is that extraordinary circumlocutions are occasionally required to refer to new phenomena. Your characters may or may not be aware that they have been so limited; the ones who are aware (if any) might wonder if there are words or concepts that they cannot express, and why that might be the case.

I'll summarize and expand on all the ideas:

Useful Artifacts - Having existing systems or technology which is voice-activated and widely available could keep certain aspects of the language alive. Namely, those which are required to interact with the useful systems. Issues:

• Technology may get destroyed.
• Technology may be stolen away from the majority.
• Technology might get lost.
• Translation or delegation services.
• Language could be avoided in all other cases.

Robotic Teachers - Having an automated education system left behind would help ensure the ability to learn the language. Incentivizing or enforcing the learning process could help with adoption. Issues:

• Educators may get ignored if incentives or enforcement is not strong enough.
• Outright revolution/revolt could occur.
• Access may be restricted or hidden.
• Any technology could break down.

Universal Communication - Having a way for different cultures to communicate across space-time could form relationships that would help to standardize the language or spread the ancient AI language. Issues:

• Of course, it doesn't discourage other languages developing locally.
• The ability might be hidden or restricted by a government.
• If it's technology based, it could break down.

Sacred Religious Text - Many examples allude to using a text or book written in a particular language to keep that language alive. There are some examples like the Quran where this works. Issues:

• The book could easily just be translated to a new language (like the Bible).
• All copies could be destroyed or burned.
• It doesn't cover spoken words at all.

Genetic Encoding - This idea was to encode the language in the DNA of creatures such that it would be passed from generation to generation automatically across all planets. Issues:

• DNA is subject to mutations. A mutation could easily remove the DNA sequence for language. Then it's up to natural selection (or maybe a genocide) if that's advantageous or not.
• Potential conflict with free will.
• Potential for surgery to cut out the language modification. More advanced races may find ways to genetically modify themselves.

Mechanical Attachment - This is similar to the other ideas, except that the mechanisms or devices are physically attached to the creatures. Issues:

• How does it get attached when new generations are born?
• It adds weight and burden to constantly carry that around.
• Perhaps the device could be surgically removed or broken.

Here's a new idea which is a hybrid and resolves may of the issues above:

Self-Replicating Modules - These modules communicate with one another and are programmed to replicate automatically if they detect less than 3 devices within 2 kilometres. One of the powers the devices provide is a shield ability, that protects the holder against almost any force in the universe. Another power is the ability to communicate with other beings within a multi-lightyear range using quantum entanglement. They are basically indestructible, and randomly teleport hundreds of kilometres (increasing exponentially) when unused for more than 10 years or placed in the same meter as more than 100 other devices.

The devices have an easy to use interface to teach the language, and the only way to interface with the devices and access their powers is through the language. They contain a wealth of knowledge on a vast array of useful subjects, all in the language of the AI.

The story takes place on a planet ravaged by a nuclear war, which is blamed on the devices (as they taught them the physics needed). Many of the devices and citizens were blasted into space (shielded by their devices). Those who survived, starved in the deserted planet or vacuum of space. The few remaining descendants who managed to scrape some food together and formed the last remaining city vowed to bury their devices and never share with their descendants, out of fear of the situation repeating itself. They set up a small box which would endlessly use the devices, powered by nuclear energy that could outlast their sun. Gradually the planet recovered, and life began anew. All the devices remained buried deep under the ancient city, then abandoned. The language was gradually forgotten, merged into new dialects and separated. It would be thousands of years before a dig team from a diamond mining expedition would uncover the first one...

If you have extreme longevity in your universe (i.e. biological immortality), then language could be to some extent fixed by the speakers who are alive for the longest time. Meaning in language is achieved through negotiation between speakers; if new generations wanted to communicate, older generations would have the upper hand in that negotiation and impose their form of speaking, especially if the increase of population is not explosive (the rate of people speaking the status quo version would be immense). People do invent new words in their lifetime, but language within a generation stays mostly the same.

Another venue is to have to constantly interact with the language in a fixed form, i.e. documents, TV, androids… you name it. This however might lead to a separation of the language into official standard and very different spoken vernacular (see how Arabic used to be standardized language, then a bunch of dialects, and now a bunch of languages).

To an extent I think people are always going to create new words - even if it's just adopting babytalk words to mean, say, 'grandma' and 'grandpa'. But if you want to cut down on it, as well as adopting one or more of the great suggestions already made, you could institute a governing body for the language itself. France has one (so do other countries, but my high school French teacher only mentioned that one and that's how I know about it), and it's one of the (many, many) reasons that Parisien French and joual (Quebecois French) are so different. Joual has a lot of slang and borrows heavily from English, and Parisien French does that... well, somewhat less, anyway.

So maybe it's possible that the nurse AIs instituted a similar body when they were creating/teaching 'culture' to these civilizations - only way less reasonable and more powerful. Especially if you combine this with other suggestions, like encoding the language into something culturally important (religion has been mentioned a lot, but it could be something else), you might find your way at least partly to a justification, and you can keeping working on it from there.

I guess it would be how they explained the English language in Star Wars, as simply, "Galactic Basic". Every race defaults to a single trade language (English). Or, in your case, a language provided by the AI. Everyone has access to and speaks this progenitor language in order for communication to be simple and effective across borders and cultures. Different permutations would still exist within and between different races of people. It's like French and Creole.

# A Grim, Deterministic Universe where Transmission of Very Precise Information determines Survival:

The worlds your AIs dropped these humans are NOT pleasant paradises, but tough environments where humans rely on equipment and technical manuals to stay alive. There's little oxygen, terraforming takes thousands of years, it's brutally cold or hot, or people must live in orbital environments and are completely dependent on equipment to stay alive.

People don't spend their days coming up with art, or inventing new science that is better than what came before. People spend their days working hard, building and repairing machines and using the infinitely superior knowledge passed down from their ancestors (in this case, the AIs) just to survive. ALL technical knowledge is enshrined in the manuals left by the AIs. There's endless entertainment and literature available - in the universal language. Text books are in the language. To vary from the language is to risk misunderstanding and immediate death for you and everyone you know.

It's also a small-scale universe. Until recently, most colonies had little or no contact with other colonies on the same planet, let alone any other world. There isn't a lot of need to spread new ideas - after all, a neighbor you don't know may be out to steal your hydroponic farm or oxygen scrubber. But you don't see your neighbors very often, and when you do, something is probably horribly wrong. Your life depends on being able to communicate survival information flawlessly and share complex equipment without training. There are no universities and no public schools - after all, the computers are there to teach you everything you need to know, and they are cranked out of identical designs and downloaded with identical software people barely understand the inner workings of.

Industry is also local. The universal assemblers are programmed to produce a pre-set set of equipment, and all instructions and operations are in your universal language, and they assemble equipment that is all programmed in the universal language. Robots that keep you alive are made from flawless pre-programmed designs, and messing with their programming language or vocal inputs and outputs introduces fatal flaws which kill people.

So any society that varies that language is under an extreme survival pressure to conform to the existing language exactly. Each variation means they can't communicate with neighbors, use essential machines, or understand the technology to adapt to the brutal reality of living on the edge of survival in a universe poorly adapted to human life.