Sign language is typically associated with Deaf people, but in reality, it should be more broadly associated with humanity at large, as it has been used across various contexts and historical periods, even within different hearing communities. Think of the monastic sign languages of medieval Europe, the signa loquendi that accompanied vows of silence in many Benedictine and Trappist monasteries for centuries, or the sign languages of Native Americans used as a lingua franca among the plains to ensure mutual understanding between different groups. There are also the sign languages used by Australian Aborigines, tied to specific speech taboos or employed during hunting, when silence is crucial. 

But what do we know about the origins of sign languages? We know a lot and very little at the same time, but we can attempt a rather realistic reconstruction of the journey sign languages of the past have taken to reach us today. The presence of Deaf people communicating with various forms of gestural language is certain, as it appears in all ancient sources, including the Bible, Greco-Roman classics, and early Christian sources. All indications point to the presence of adult Deaf individuals, sometimes alone and sometimes in small groups, who used hand gestures to communicate with their interlocutors, despite lacking oral articulatory capabilities. 

However, it was necessary to wait until the Enlightenment and the opening of the world’s first school for the Deaf to see the emergence of the first modern sign languages. These languages are closely linked to the first institutes, which were not only places for educating the Deaf but also centers of socialization, aggregating for the first time in history a significant number of Deaf individuals in one defined space. These Deaf institutes essentially represented the first formal deaf space in history and enabled the creation and preservation, both socially and materially, of the Deaf community as we know it today. While early attempts to educate the Deaf date back to 16th and 17th century Spain, the world’s first true Deaf school was the Institut National de Jeunes Sourds de Paris (still in existence!), founded in 1778 by Abbé de l’Épée. The uniqueness of de l’Épée’s project lay both in its organizational model and its educational method. Unlike the one-on-one tutor-pupil model of previous Spanish attempts, the Parisian school was structured as a formal educational institution with a boarding component, where Deaf people could interact in one place, allowing their mimic-gestural communication to “explode” and evolve within one or two generations into a full-fledged sign language. 

This phenomenon occurred in Paris in the late 18th century. Abbé de l’Épée abandoned the oral methods of his predecessors and instead made sign language the primary tool of Deaf education. This practice continued for about a century until the controversial Milan Congress of 1880, which, in the full swing of positivism, mandated a return to oral education for the Deaf, effectively banning sign language use, at least in educational settings. It wasn’t until William Stokoe’s visionary studies, beginning in the late 1960s in the United States, that the linguistic value of sign languages was rediscovered. These studies, mirrored in Italy a few years later by Virginia Volterra, marked a significant shift. 

De l’Épée welcomed many young Deaf people into his new institution, some of whom likely already knew each other from their communities or family ties. These children brought what de l’Épée identified as “natural signs.” With his classical philosophical education, he had a clear hypothesis that signs could perform functions comparable to words, allowing him to see what others had either failed or refused to recognize for centuries—that Deaf people could communicate through visual-gestural channels and be understood through body and facial expressions and a repertoire of iconic signs often shared with and understood by hearing people. This wide range of spontaneous signs left him amazed and convinced him of the powerful potential of this form of communication for Deaf education. Soon, he formalized a new method of Deaf instruction, known as “methodical signs,” where he used natural sign language as a bridge to write French, adding his invented “signs” for all parts of speech present in French but absent in sign language. 

Through the use of natural signs combined with methodical signs, the French Sign Language emerged and quickly stabilized through a rapid process of creolization. French Sign Language served as a model for many other sign languages around the world. With some approximation, we might call French Sign Language the “Latin” of sign languages, as it is the oldest and most prestigious and has given rise to many other sign languages. This was possible due to de l’Épée’s generosity and enthusiasm, as well as his tireless outreach, which included hosting Deaf educators from other European countries and publishing two significant pedagogical works that remain foundational in the field of special education. 

Thanks to this openness, French Sign Language first influenced, or directly spawned, many European sign languages during the 19th century (with notable exceptions like British Sign Language and German Sign Language), and eventually American Sign Language, which has since spread in various forms to numerous countries in Africa, Southeast Asia, and Central and South America. 

But what were the “natural signs” that so astonished de l’Épée, and where did they come from? Although he couldn’t have known, we now know, thanks to contemporary linguists, especially those with an innatist perspective, that what de l’Épée observed are what we now call “home signs”—a precursor to sign languages. These home signs arise spontaneously in situations where Deaf children have no exposure to language, whether spoken (due to an inaccessible auditory environment) or signed (because unknown to their family). This results in an instinctive visual-gestural communication that gradually becomes grammaticalized, creating a primitive visual-gestural language with both lexical (signs in codified gestures) and syntactic elements, which form basic sentences. The result is that between the child and their closest interlocutors, an instinctive visual-gestural form of communication emerges, which gradually becomes grammaticalized, taking the form of a kind of primordial visual-gestural language. This includes not only lexical elements (i.e., individual signs in the form of codified gestures) but also syntactic elements, with which basic utterances are constructed—perhaps just one, two, or three terms, but still genuine sentences. Home signs, likely in even more elaborate forms than described so far, are almost certainly the sign languages observed in the past and mentioned in ancient sources. Perhaps even more than that, in some cases, these home signs might have evolved in the past to reach an evolutionary stage similar to what we know today as ‘Shared Sign Languages’ or ‘Village Sign Languages.’ These emerge spontaneously as an evolution of home signs, where the presence of Deaf people becomes the norm (typically due to the limited genetic diversity in such populations), and their numbers grow to represent a significant portion of the population. They are called ‘shared’ because they do not hold the status of languages exclusively for the Deaf; instead, these populations experience a balanced diglossic situation between spoken language and sign language, with the latter being used by the hearing population as well. 

So, have sign languages always existed? In practice, we could answer this with a resounding “Yes!” although, of course, many sign languages of varying evolutionary and complexity levels have emerged and disappeared over time, with only faint traces in historical sources. However, with the advent of Deaf education in the late 18th century, things changed drastically, and modern sign languages, as we know and study them today, began to take shape.