Language doesn’t have to be spoken. We’ve discussed written languages before, in the context of books and literacy . . . but it’s also possible to communicate through the body, in ways far more complex than what we usually mean by the phrase “body language.”
We don’t have great evidence about the history of signed communication. Writing systems were mostly designed with an eye toward representing speech sounds, not gestures, and obviously the movements of the body don’t leave much physical evidence that archaeologists can dig up. And like low-prestige basilects, these methods have usually not attracted the kind of attention and respect that means someone will go to the effort of recording how they work.
But we do know that visual-manual communication goes back a long way. Deafness and muteness are not new phenomena; if anything, they might have been more common in the past, given the possibility of things like untreated diseases causing hearing loss. Since many people were illiterate, communicating through writing wasn’t an option, so they looked to other methods. The earliest reference to using gestures for this purpose comes from the writings of Plato in the fifth century B.C.E. He doesn’t give any details, but he makes it clear that it was a known practice among people who couldn’t speak.
I should pause here to note that sign languages aren’t limited to the realm of disability. Quite apart from the modern debates over how we classify disability in the first place, there are other groups who have found the idea of gestural communication useful. For example, some Christian monastic communities developed systems of sign to use during periods of silence. Soldiers in the field also benefit from such things, either because they don’t want to give their position away to a nearby enemy, or because there’s enough noise that speech might be lost or misunderstood. There’s even evidence that at the Ottoman court, Deaf servants were preferred because they couldn’t overhear conversations — and then the signs developed to communicate with them came to also be used between hearing individuals, I imagine again due to the benefits for secrecy. (I immediately wonder how many of those servants learned to read lips . . .)
Systems like monastic or military sign tend not to be full languages; they’re more like codes used to represent a limited range of topics from a shared tongue. But the indigenous people of the Great Plains have a sign language that was once employed as a lingua franca through a large swath of North America, and that one does have all the features of a full language. In other words, it has its own grammar and lexicon, which doesn’t simply map as a representation of the spoken language of any one group.
Getting to that level of complexity seems to be rare before the modern day, though we can’t be sure how much the imperfect evidence biases that conclusion. Most of the evidence we do have is for manual alphabets, i.e. methods for spelling out spoken words using the hands. These can be tactile (meaning you communicate through touching the other person), but a lot of the early British ones seem to have gone the route of having the signer use one hand to point at different parts of the other hand — there’s even some interesting speculation that this is derived from a manual code for the Ogham alphabet. Another system, developed in the late nineteenth century, operated on the acrostic principle of pointing to body parts that began with the desired letter. As with the Ottoman courtiers, those with disabilities weren’t the only ones to use these systems; they had utility for anybody who wanted communicate silently.
If you study a modern sign language, though, you’ll find that finger-spelling is only one tiny part of a very complex whole. Full systems of gestural communication, complete with grammar and features not pegged to the representation of a particular spoken language, seem to arise when you have not just a few individuals who need to get by in a world of hearing people, but a whole community where deafness is prevalent. The island of Martha’s Vineyard, for example, had enough Deaf residents (more than thirty times the national average in the mid-nineteenth century, and higher still on some parts of the island) that it’s known for developing its own sign language, which was in common use for roughly two hundred years.
A full sign language also goes somewhat hand-in-hand with societal attitudes toward deafness and muteness. In Europe, the assumption for a long time was that such people were mentally deficient and couldn’t be educated — or possibly even saved, in the theological sense. The Catholic English saint John of Beverley taught a Deaf person to speak in the seventh century; apparently his friend the Venerable Bede considered this one of John’s miracles. The Spanish Benedictine monk Pedro Ponce de León (not to be confused with the conquistador Juan Ponce de León) is remembered because he made the unusual decision to dedicate himself to the education of Deaf children, swimming against the tide that said any such effort was a waste of time. The florescence of European experiments with manual spelling and more complex communication coincides with the improvement in attitudes toward people with disabilities. By contrast, Native American communities didn’t generally assume that deafness or muteness implied any mental defect — and thus systems like Plains Sign Talk flourished much earlier.
The importance of this is huge, for people with some degree of hearing or speech difficulty. We’re social creatures, and we depend on communication to understand the inner lives of the people around us. If you can’t communicate, then you’re cut off from much of society, often with massively detrimental consequences not only for your mental health but for how other people treat you. This is why Deaf communities can be so vitally necessary, along with places like Martha’s Vineyard, where the hearing community also learns and uses sign language.
As with so many things I mention in these essays, though, I see very little of this in fiction. David Eddings’ Belgariad and Malloreon series stuck in my head at an early age for their manual code — but that was only in the context of spies and merchants wanting to communicate discreetly, with gestures that a non-initiate might not recognize as meaningful. The rebooted narrative for the game Legend of the Five Rings is remarkable for including not one but two sign languages, developed by different groups within the Empire, and used by both those with hearing difficulties and those without.
Given how rarely fantasy and science fiction have historically tended to look at topics of disability, it isn’t surprising that we don’t have many examples of fictional sign languages. Even when the story doesn’t feature a Deaf character, though, the above makes it clear that they don’t have to be the only ones who use such a thing. Hearing characters might learn sign for communication in various contexts — and even a passing line noting the origin of that language will imply a huge amount about how their society treats Deaf individuals.