Suppose human beings have evolved markings covering the face and hairs. The cells contain a colony of bacterium capable of producing multiple arrays of visible light. Each bacteria reacts differently to a variety of chemicals secreted from our sweat glands. This complicated mixture of chemicals is controlled by our emotional states as well as the environmental factors such as humidity and temperature etc.

How can the complex brilliant display of bio luminescence be incorporated into our written language and what will it look like? Not to be confused with camouflage(chromatophores).

  • $\begingroup$ I'll retract that. My thought was that there would be many ways to incorporate color signals into language so it might be difficult to get a conclusive answer. $\endgroup$
    – Skye
    Oct 3, 2016 at 13:10
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    $\begingroup$ I think I read something like this with dragons in a book when I was REAL little. They had control over which areas lit up, and it allowed for communication underwater, given how these were sea dragons. Do your humans have control over individual areas where they can glow? $\endgroup$
    – Pleiades
    Oct 3, 2016 at 13:13
  • $\begingroup$ You didn't really need to go through the process of re-inventing chromatophores for this question. You're describing chromatophoric communication, so the answers will be the same anyway. It's ok to express your questions in simple terms without having to shroud a wheel inside a re-invented wheel. $\endgroup$
    – user10945
    Oct 3, 2016 at 13:28
  • $\begingroup$ When did this capability enter the genetic line? Do all animals have this capability or was this introduced into humans a mere 100,000 years ago? $\endgroup$
    – Green
    Oct 3, 2016 at 14:10
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    $\begingroup$ On a related note: We communicate with facial expressions and body language, but those have only entered written language in the form of emoticons/emojis relatively recently. I expect that the changes related to bio-luminescent expression would most recently have expressed themselves in the form of varying font colors. $\endgroup$
    – Brian
    Oct 3, 2016 at 19:57

6 Answers 6


This will have significant effects on human society, far more important than its effects on written language. Everyone basically has a polygraph built into their face. There will thus be social conventions about when it's permissible to cover one's face, and these will probably make social status very important. You need to consider this carefully in writing about these people.

I'm not sure that written language will capture much of this mode of expression. Since it's basically involuntary, and probably isn't completely standardised between different individuals, it's only really meaningful when recording an individual event, rather than the more abstract uses of language. So it may well turn into some extra descriptive adjectives, as AndreiROM suggests, or something equivalent, like emoticons.

There's an analogy in all the things we can do in speech that aren't written down as part of all text. Different tones of voice, deliberate changes in timing, different emphases, and so on let us convey a lot about how we feel in addition to the content of the words we speak. But this is rarely written down, and when it is, it tends not to be mixed in with the words.

So the effect of this on written language may not be large. The effects on how people communicate face-to-face, however, will be huge.

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    $\begingroup$ Not necessarily, I bet politicians could control their markings on their faces in that world. $\endgroup$ Oct 3, 2016 at 20:10
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    $\begingroup$ The Yilanè from Harry Harrison's West of Eden series (evolved dinosaurs on an Earth not struck by an asteroid) have a language such that they literally cannot lie... so they do a lot of lying by omission. (They actually don't even have a word/concept for lying - which is key to the plot.) $\endgroup$
    – Ghotir
    Oct 3, 2016 at 21:03

It might not have any impact. Human beings can gesture with our hands, but although we can use our hands to emphasize our speech, it doesn't really change the communications. The only non-constructed language I've ever heard of where hand position impacts the spoken words is pre-telephone dialects of Portuguese. There may be others, but they aren't common.

Just because we can use a signaling mechanism doesn't mean we will.

Or we might - facial expression, vocal pitch, and other signals DO commonly impact the spoken words. I think this is something you as an author can play any way you want.


Any number of conventions might arise. For example:

I feel so overwhelmed! [magenta]


I feel so magenta-overwhelmed!

Alternatively, things might not change much at all:

The premier's message was one of unity on this dark day, his powerful message being reinforced by strong, confident hues of blue, and deep purple as he addressed the nation.

It really depends on how complex those bio luminescence patterns are, and what sort of depth you want to go into when describing them.

  • $\begingroup$ I wonder how this would affect synesthesia? $\endgroup$
    – Skyler
    Oct 3, 2016 at 18:06

Written language conveys ideas. For a variety of obvious reasons, writing combinations of simple symbols is easiest, and changing the situation probably won't change that result. Maybe "$" means "literally-green-with-envy", but it's still going to be an easy-to-reproduce symbol.

For storytelling purposes, you want to sidestep all this, and just use English (or whatever). As Asimov lampshades in Second Foundation (emph mine):

The Student smiled shyly, and the First Speaker responded by saying, "First, I must tell you why you are here."

They faced each other now, across the desk. Neither was speaking in any way that could be recognized as such by any man in the Galaxy who was not himself a member of the Second Foundation.


The same basic developments of mental science that had brought about the development of the Seldon Plan, thus made it also unnecessary for the First Speaker to use words in addressing the Student.

Every reaction to a stimulus, however slight, was completely indicative of all the trifling changes, of all the flickering currents that went on in another's mind. The First Speaker could not sense the emotional content of the Student's instinctively . . . rather he deduced them, as the result of intensive training.

Since, however, it is inherently impossible in a society based on speech to indicate truly the method of communication of Second Foundationers among themselves, the whole matter will be hereafter ignored. The First Speaker will be represented as speaking in ordinary fashion, and if the translation is not always entirely valid, it is at least the best that can be done under the circumstances.

It will be pretended therefore, that the First Speaker did actually say, "First, I must tell you why you are here," instead of smiling just so and lifting a finger exactly thus.


Verbal vs Non-verbal communication

What you are describing is just a more pronounced form of what we already deal with when it comes to written language versus spoken. Body language, tone, inflection, gestures. There are any number of non-verbal cues that we have evolved to use and understand which have them been adapted over to the written word.

In the world you describe, written language would only have to be slightly shifted to accommodate the new facial markings. If you are writing about someone who is angry you can mention their volume and tone, or that they have clenched fists, or that their face flared crimson (or whatever the accepted display for "anger" would be). Those first two would work in our society because we understand that angry people shout and make fists. The third description would work because people in your setting would know that angry people have literal red faces.

Here is a quick and simple exercise that might help you get a feel for what writing in your setting looks like: Pick any piece of writing today that focuses on character descriptions, what they are saying and doing, and then try to replace each of the descriptions with the appropriate visual cue that someone in your setting would have. Once you know what different emotional responses look like you can start to use those as replacements when talking about in-story text. Where we would say that someone sounded sad, they could say that the person looked blue (or, again, whatever the response is).

If you just need an idea of what written language would look like in your setting, that should be a good enough start. If you actually plan on showing off that written language then you would need to do a bit more work. First introducing readers to the visual cues and what causes them, and then making sure that you incorporate them often enough that it feels like a natural thing. Remember, humans have very good grasps of what these non-verbal cues mean. If you see someone grinning you know that they are most likely happy. If someone in your setting sees someone flashing yellow and pink, they would be just as confident that they knew why, and a writer would be just as likely to use that as a shortcut that the person is happy as we would say that they were grinning.


Bio-luminescence by the mechanism you describe would act too slowly to keep up with the pace of human verbal communication. That rules out using the colors as an extension of language, for example in place of the tones in a tonal language like Chinese and Narrow Bantu, or in place of the genders of a highly gendered language like Latin or Sanskrit. The user wouldn't be able to change 'tone' or 'gender' fast enough to keep up with speech.

Color changes would be fast enough to express emotion in speech. Irony, Confidence, Humor, Satire, etc could all be indicated by bioluminescent changes. However, this has the drawback of not being as visible during the daylight, and harder to see from a distance. If a general is giving a speech to 5000 assembled troops, its hard enough for everyone to hear him, much less to see his steely blue confidence.

The last option is as a sign language of sorts. In West Africa and among Aboriginal Australians, there are 'home sign' systems which closely replicate the full complexity of a natural language, and which some think could have co-evolved with spoken language.

The most reasonable explanation for light based communication, then, is that your people originally used bio-luminescence as a means of communication such as chimpanzees or gorillas communicate to each other. Then, as the species evolved human language with its emotions and abstract concepts (things that are absent in animal 'languages') the bio-luminescence co-evolved as a 'home sign' language. While perhaps not expressing a full range of concepts like a real language, it could express a limited subset, especially since the 'bandwidth' of sharing thoughts would be lower than with a verbal language.

Even more interestingly, it could be that the bio-language and verbal language diverged, so some groups have different verbal languages but can 'light talk' to each other when they trade. Or you could even say that the bio-language is genetically determined, and when two people can't speak to each other, they can resort to ape-like bio-luminescent communication.

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    $\begingroup$ You make some good points but "sign language for the deaf is not truly a language, bucause it lacks the grammatical lexemes that would allow it to extend and adapt itself. " is not correct. Here is an explanation of the grammar of American Sign Language. Here is a paper "On Defining Lexeme in a Signed Language" referring to ASL, BSL and Auslan among others. Sign languages evolve all the time. $\endgroup$ Oct 3, 2016 at 18:03
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    $\begingroup$ Could you cite references for your claims about sign language? Every document I've seen has a very different opinion of sign language than you describe here. $\endgroup$
    – Cort Ammon
    Oct 3, 2016 at 19:13
  • $\begingroup$ @Lostinfrance While I am not completely abandoning my characterization of sign languages as not natural languages, that is certainly a hotly disputed argument. In addition, I have just learned that many think that there is a gestural substrate to spoken language; that is, spoken language evolved from gestural. I have removed the relevant references until I can make a better argument. $\endgroup$
    – kingledion
    Oct 3, 2016 at 19:53

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