Human (spoken) languages have a great variety in terms of grammar and what the basic elements are, but they have essential features in common in terms of being a time sequence of phonetic primitives, which are sounds involving both AM and FM modulation of basic sounds that the vocal apparatus can make.

If an animal that communicates via scents were to develop intelligence and a “full language” evolved from the system originally used to communicate a few basic ideas only, how might that work?

How could smells be built up into complex patterns? In what ways would it be different from the implicit assumptions we have concerning language, since we use sound?

  • $\begingroup$ @James still have an idea for this? $\endgroup$
    – JDługosz
    Jun 7, 2017 at 15:22
  • 1
    $\begingroup$ As a matter of fact I have something in mind yes, I will start writing it up $\endgroup$
    – James
    Jun 7, 2017 at 17:46
  • $\begingroup$ @James did you get back to this? $\endgroup$
    – JDługosz
    Nov 3, 2017 at 17:45

6 Answers 6


Smells are hard to change quickly. Put too many smells into a conversation and you'll quickly lose track of the "words" like how we lose track of a conversation in a noisy room.

One key evolution for this would be to smell shorter lived compounds. We smell mostly long lasting compounds because they are the most useful to smell in our world. If conversation was important, one would develop sensitivity to smells with a much lower half life by necessity.

The other key would be that conversation would be more fluid. Think of a conductor gently wafting over the orchestra, bringing out subtle notes of violin and viola. An angry response might bring out the shrill note of a muted coronet, a more mellow one may not give the coronet a signal (leaving the coronet to play their line out quietly), and instead signal to the clarinets to signal sympathy leading into an accelerando to bring an insistent tone to the oboe solo coming up.

These creatures would probably not break apart their communication into clean crisp words, but instead focus on fluid and constantly shaping ideas forming as a culmination of the flow of the dialogue.

  • $\begingroup$ I don't think it would work. Odors persist, so to continue your musical analogy, trying to converse by smell would be like feeding your orchestra's output into a not-well-damped reverb circuit. $\endgroup$
    – jamesqf
    Dec 20, 2016 at 3:20
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    $\begingroup$ @jamesqf That would be my second paragraph. Orders persist because the molecules we found worth smelling are the long lived ones. However, this is mitigated by the nature of smell. While the number of smells you could put out may be limited, its worth noting that smells are a much higher bandwidth channel. The room for nuance is pretty amazing. What we need 100 words for may be 1 or 2 scents. For proof, just read a review of a wine and look at all the effort it takes to describe the taste/smell. $\endgroup$
    – Cort Ammon
    Dec 20, 2016 at 3:23

Language, as we know it, is a combination of sounds made in rapid succession. We are able to understand multiple sounds at once but we are not necessarily very good at it, we are able to tune in to a single source when listening to speech. With that being said, it would be easy to develop a language of smells by simply switching out human-made sounds for animal-made scents.

Of course, the range of smells which an animal can both produce and sense must be accounted for, which would be the most difficult, seeing as we don't have a very good way of cataloging smells nor knowing exactly what we're missing out on. But with that being said, this simply means there's lots of room for creativity.

If you do plan on including this in some recounting to an audience, be it by a faux-manuscript or book, you will need to think about how you will describe this system effectively so that the reader understands it.


Humans can differentiate dozens of smells and things can smell similar but slightly different to something else. This is enough to start a language if you can reliably make and clear those scents.

Maybe each kind of smell is a different part of speech; Let burning different woods be nouns, burning flesh of different animals be verbs, hot clay or rock be adjectives and say burning hair be the clearing scent. I could have a vocabulary of a couple dozen words able to form hundreds of sentences which may be enough for rudimentary communication and I'd assume your people have better tools to work with than I do.

Let your people have control of scent creation and differentiation, and superlative skill need not come all at once. Simple communication is better than none and each increase in skill with scents will obviously improve communication.

Now clearly these people need a scent gland, but how ought it to work? It could be it releases a scent then another then another and so on until the clearing scent, a bit stream much like how our speech works. But maybe it could also work as bursts, if you want to keep their language like ours you could let there be subtleties of scent to signal grammar marks so the even though it arrives together there is no doubt about what dies when a panda eats shoots and leaves.

If we say a human can smell 50 different things and a dog (a stand in for a smell-talker) has 50 times our sensitivity that might be 2500 'words' which might be a little limited for a modern person, but if we say they use scents like we use frequencies that's like having 5000 phonemes (human languages have up to about 100) So if they could catch a new scent 1/20 as fast as we can hear a new sound they could copy our language. And theres certainly no reason to think dogs are at the limit of smelling.

There is considerable doubt about what scent is, which means that the bandwidth of scents is not really limited. Let the scents get really complicated. Let the scent encoding and decoding glands be more complex then the brain. Let scents pass thoughts.

But lets get back to my fire-scents. This could be enough for a real language. Hawaiians use 11 phonemes, so if you can tell four kinds of wood, four meats and three baking clays apart you could recreate the Hawaiian language in smell. It probably takes 100 times longer or more to clear a scent then to hear the next sound so you may be all day exchanging greetings, but maybe your people aren't that interested in talking fast. If the scents carry over a wide area it may be the whole tribe is all day having a quaker meeting as they do all the normal things of living.


This is incredibly similar to human speech, so it's easy to imagine.

Humans create individual sounds, then combine them and alter volume to change the meanings produced. We also listen for sound waves that we can recognize, and interpret a meaning similar to that which we can make.
All you need is a creature with the ability to produce distinct smells, and the ability to interpret scents produced by other individuals, to get your system going as effectively as human speech.

Examples in nature and applications

The Wikipedia article on Pheromone has the following definition:

A pheromone (from Ancient Greek φέρω phero "to bear" and hormone, from Ancient Greek ὁρμή "impetus") is a secreted or excreted chemical factor that triggers a social response in members of the same species.

Nature already has scent-based communication, and it's practical for anything larger than a couple cells. Pheromones are used to communicate anything from the location of food to the desire to mate, and could be diversified and combined just like human sounds as a language develops. They could even contain chemicals characteristic of a specific individual to show an "identity", just like how different people have different voices (and smell different).

An interesting quality of this communication is that while sound waves dissipate relatively quickly, scents can linger, and even travel great distances. Some species have honed smells surpassing six miles on land, and it is disputed as to whether similar distances can be achieved accurately underwater by other species (sharks?).

Evolutionary feasibility

The problem with creating a scent-based system, despite the fact that it can communicate messages, is that it may not evolve easily. Verbal communication vibrates an existing membrane - a relatively small use of energy - and color or light-based forms of communication are not intensive on the body.

To go through an entire day speaking with scents, however, an organism must consume all the right ingredients, in abundance, then convert them into the appropriate chemicals. This is, compared to other means, a lot of work, and it may be why current organisms that use pheromones have not developed complex speech.

To evolve a plausible scent-based communication system, you need easy access to food, and a lot of whatever chemical you choose to lose, but on the whole, it's not impossible.

Edit: As @AndreiROM points out, conversations with scent may get "noisy" but I'm sure there are compounds that dissolve fairly quickly - or changes in the ways smells are processed to ignore them after initial exposure - that can easily account for this.


The main problems are:

  • scent lingers
  • scents mix with previously emitted scents or ones from non-language sources leading to
  • it's very hard to get a quick change from scent to scent, neccesary to transfer information quickly.

One way around this that I can see is... to make it less "scent" and more "taste".

Smell not with a nose, pulling in air that carries chemicals, but with antennas that can analyze the smells in the air for important, vague concepts ("hear" someone "shouting"), but are also able to quickly analyze the rapidly-changing surface chemicals on another person's scent-emitting gland.

So, examples:

"Danger!" would be a smell in the air. Simple concept, important to quickly communicate.

"Want to meet up next thursday for some tasty food at Jon's place?" would be a longer chain of different chemicals, quickly pushed out and neutralized again, on the forehead (or butt, or wherever) of the guy you're currently talking to. Probably because he sprayed "I want to talk" into the air.


In what ways would it be different from the implicit assumptions we have concerning language, since we use sound?

Verbal language has many components. These components can be arranged in many ways in order to put some sense on the environment. For example, if you are car shopping, you need different names for the car, the door of the car, the price of the car, the suspension, comfort, price, colour, the type of fuel it uses, efficiency, age, price, capacity. . . .

A naieve scent-based language replaces each name with a scent. A conversation consists of two individuals exchanging short puffs of scent at each other.

However scent based language does not need so many names because it can interact directly with the environment. Rather than saying "Car door is good" you spray the door with the scent for "good". To say "Car door is very good" you spray the same scent with greater potency.

The speakers have very sensitive noses/tongues/antennae and can at shot range distinguish between different scents sprayed on different parts of the car. TO communicate at long range you need an extra large cloud of scent. "Shouting" like this is considered rude as it disrupts all nearby more delicate scents.

You have a smaller vocabulary but a greater number of ways to use each word. You could probably get by in a conversation with 5 or 10 words which carry no primary meaning alone, and only gather meaning when sprayed on two separate pieces of the environment. The thrust is either "these are similar" or "there are different". With enough reflection you can realise this is not too far off how humans communicate. We mostly just draw parallels between different things.

Consider how an ant colony self-regulated by pheremones.

Abstract concepts are harder to convey. To overcome this fact you have to get to the root of why abstract concepts are necessary in human conversation, when any outcome of the conversation can only be concrete and not abstract.

Spraying the scent for "bad" on someone has extra impact due to the physical violation required.

In spoken conversation it is considered rude to suddenly change the subject. The polite thing is to follow on directly from the other person's last sentence. Or at least seem to. Most 'etiquette' is a way of circumnavigating this fact.

By comparison, in a scent-converation every word lingers in the air. "Car door is good" remains visible long after it is spoken. At any point someone can go back to the door and spray on another scent to resume that thread of conversation. Thus scent-based conversations would have a degree of nonlinearity about them not present in verbal conversations.

Exercise: How can remote communication function for this language. A smell-making device is a must. But how does it capture the different locations of scents when the speakers are in different environments?


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