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Smiling multiracial friends talk using sign language

Did We Learn Sign Language Before We Learned to Speak?

The idea that humans first communicated by complicated gestures and only later learned to speak is popular among cognitive scientists. Kensy Cooperrider explains
Cognitive scientist Kensy Cooperrider

The origin of language is considered one of the hardest problems in science. Like the origin of consciousness, it attracts a great many theories. Cognitive scientist Kensy Cooperrider is a stout defender of the idea that human language started as sign language—a gestural “protolanguage” —hundreds of thousands of years ago.

It’s not a new idea. It goes back to Étienne Bonnot de Condillac’s Essay on the Origin of Human Knowledge (1746) and remained popular in the 19th century. In the 20th century, it was championed by University of Colorado anthropologist Gordon Hewes (1917–1997), who introduced the idea of studying ape communications in the early Seventies, to gain more insight. In general, apes communicate more by gesture than by voice. An early research subject was the chimpanzee Viki:

Vocal language, it would seem, was out of reach for apes. But gestural language proved to be another matter. Another couple carried out a similar home-rearing experiment with a different chimpanzee, Washoe, but used manual signs borrowed from American Sign Language instead of English words. Washoe’s linguistic capacities blew past Viki’s. She ultimately mastered some 350 signs – nowhere near the level of a human signer, of course, and with none of the grammatical sophistication, but impressive nonetheless. Subsequent studies teaching signs to other apes – including Koko, a gorilla, and Chantek, an orangutan – enjoyed comparable successes.

Kensy Cooperrider, “Hand to mouth” at Aeon

Essentially, the question depends on whether largely unknown human ancestors from millions of years ago signed or spoke—or perhaps both or neither:

The takeaway from observations of primate communication is not that ape gestures have all the hallmarks of human language – far from it. It’s that, compared with the mouth, the hands seem to be better soil for the seeds of language. Central to contemporary discussions of language evolution is the notion of our last common ancestor with chimpanzees – a now-extinct species perhaps 5 to 10 million years old. Given what we know about primates today, we can confidently say that this ancestor had gestural and vocal abilities much like those of modern chimps. Which means its hands were more language-ready than its mouth – as Hewes put it in 1973, the manual medium was the ‘line of least biological resistance’.

Kensy Cooperrider, “Hand to mouth” at Aeon

One concern should be that we actually know very little about the “now-extinct species perhaps 5 to 10 million years old” who is said to be our ancestor. Meanwhile, the initial hypothesis that the ancestor signed rather than spoke has since blossomed into “a family of related proposals.”

Cooperrider offers four arguments:

– Children learn gestures before speech.
– Gestures create more “transparently meaningful” signals than words do.
– Our last common ancestor with chimpanzees “likely had the equipment to eventually create a sophisticated system of manual signals, but not vocal ones.”
– There are a number of contemporary sign languages by which people can communicate accurately.

These arguments are, of course, debatable. Children learn as they must; their needs are not a pattern for the development of civilization. And sign languages emerged in the modern era among people who cannot use speech, not among people who simply recognize the usefulness of sign languages.

Cooperrider, who is host of the podcast Many Minds, admits the obvious problem: Everyone uses speech today, despite the claims for the advantages of sign languages. Dismissing other explanations (speech is easier for abstractions, better understood in the dark, frees the hands), he favors the explanation that speech is simply less work:

But there is at least one key feature of speech that is harder to dismiss: it takes very little effort. Attempts to measure the caloric expenditures involved in speech report that they are essentially negligible. This is both because the movements involved are so tiny, and because spoken words often hitch a ride on our outgoing breath. (Speaking can be thought of as a way of upcycling an abundant waste-product – air – as it leaves the body.)

Kensy Cooperrider, “Hand to mouth” at Aeon

“Laziness,” he says, is a huge force in shaping human behavior. There is, as he says, a natural connection between the hand and the mouth, which begins among thumb-sucking babies in the womb. But he admits that, after we get past that, the details are “highly speculative, of course.” And he acknowledges,

Ultimately, questions about modality are just one layer of the larger puzzle of language origins. Even if we were able to establish some version of a gesture-first proposal as not merely plausible but likely, there would be many more layers to contend with. We would also want to understand how we came by our abilities to read other minds, to sequence and combine ideas, to conceptualise abstractions such as ‘tomorrow’ and ‘truth’. We would need to explain, not merely whether we first conveyed meaning by hand or by mouth, but why we felt an itch to mean anything at all. It is this multilayered complexity that makes the evolution of language the ‘hardest problem in science’ – and also one of the most tantalising.

Kensy Cooperrider, “Hand to mouth” at Aeon

Ah but, to do that, he would need to get past naturalism (nature is all there is), often called “materialism.”

Before we get to how human beings decided to speak, perhaps we should first address why we did. What did we have to say that chimpanzees didn’t and don’t? And how did we come to have those things to say?

In short, the problem of language is bound up with the Hard Problem of consciousness, a shoal so treacherous that many scientists have turned to panpsychism to address it. Perhaps we’ll never know if our ancestors relied principally on sign language but language is always a fascinating topic anyway.


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The real reason why only human beings speak. Language is a tool for abstract thinking—a necessary tool for abstraction—and humans are the only animals who think abstractly. (Michael Egnor)


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Did We Learn Sign Language Before We Learned to Speak?