Does language make humans unique?

Around two hundred thousand years ago a tall, gangly, naked, bipedal ape made its entrance onto the world stage. The unlikely creature’s debut would eventually blossom into ecological hegemony with its rapid expansion across the globe a little more than 100,000 years later. As the progeny of humanity’s evolutionary saga, we consider ourselves special creatures, entities distinct from the rest of the natural world. Humans like to point to several “defining features” that sets our species apart from other organisms, the foremost being our capacity for language. But just how true is this presumption?

The predisposition for language acquisition appears to be an innate characteristic of human cognitive development. Starting around 6 months of age, babies are able to recognize speech sounds, and soon after they begin to communicate nonverbally using gestures. Children automatically learn complex principles of language, such as syntax, without any formal instruction, and kids also appear to be the main drivers of novel language development. A unique case that highlights these processes is the spontaneous development of Nicaraguan Sign Language (ISN; Spanish: Idioma de Señas de Nicaragua). In 1979, the new Nicaraguan government began introducing initiatives to promote literacy and fluency in Spanish, one of which included the inauguration of the first public school for the deaf in the capital, Managua. The first children attending the school came from diverse communities across the country, where they had only limited communication with family and their local community through series of “home signs” used to convey general concepts; upon their arrival at the school, these children were initially unable to communicate amongst themselves. But it didn’t take long for them to invent a new, sophisticated form of communication by combining gestures and elements of their home-sign systems. An important factor leading to the invention of ISN was that this school for the deaf did not teach any sign language; they focused instead on teaching the children to lip-read and speak Spanish. Consequently, ISN was created de novo, completely uninfluenced by existing contemporary sign languages. As James Shepard-Kegl, co-director of the Nicaraguan Sign Language Projects, points out, “All languages have grammar and syntax, but the first children at Managua’s deaf school had no model for how a language worked because they had been isolated from signed, spoken, and written language all their lives.” He also notes that, “A lot of those older kids weren’t generating grammar the way little kids did. They copied the grammar the little kids generated.”

So, if language acquisition is hardwired in the human brain, then it is instinctual and must be an expression of innate biological factors; these factors are tangible and can be examined empirically. One such factor is the gene FOXP2, the first gene ever discovered to be associated with language and speech – FOXP2 mutations lead to serious language and speech disorders in humans. Interestingly, this gene belongs to a larger family of transcription factors essential for regulating embryonic development known as the FOX (forkhead box) proteins. The genes that code for these proteins are highly conserved across a wide range of animal species and FOXP2 is no exception. Because the gene is so similar among different species, any genetic variation observed might explain the disparity in their communicative abilities. One study examined differences in the gene among great apes as well as variations among different human populations. The researchers found that the FOXP2 protein acquired two mutations unique to humans, at least one of which may have functional consequences. They also detected rates of genetic variability indicative of recent selective pressure in humans. Furthermore, they state that their “method suggests that the fixation occurred during the last 200,000 years of human history, concomitant with or subsequent to the emergence of anatomically modern humans, and is compatible with a mode in which the expansion of modern humans was driven by the appearance of a more-proficient spoken language.” A more recent study comparing FOXP2 mutations among extant (Homo sapiens: modern humans) and extinct (Neanderthals, Denisovans, etc.) human species throws these results into doubt, however, as they discovered that “it turns out that the FOXP2 mutations we thought to be human specific, aren’t.” Rather, we share them with archaic Homo species. Nonetheless, despite not being Homo sapiens, these species were still human.

Now, vocal learning is a rare trait shared by humans and only a handful of other animals, including some birds, bats, elephants and cetaceans (whales & dolphins).  “It is the ability to modify acoustic and syntactic sounds, acquire new sounds via imitation, and produce vocalizations”, and it represents a critical base element for spoken language. On the non-human research front, FOXP2 has been shown the be expressed in the neural circuitry of songbirds, hummingbirds and parakeets – species not linked by an immediate common ancestor, but that are all vocal learners. Another study “detected divergent selection (a change in selective pressure) at FOXP2 between bats with contrasting sonar systems, suggesting the intriguing possibility of a role for FOXP2 in the evolution and development of echolocation.” These researchers also determined that the 18 species of cetaceans they studied share the same three FOXP2 mutations, but observed no difference between echolocating toothed whales and non-echolocating baleen whales. An investigation of FOXP2 expression in elephants has not yet been performed. A review titled FOXP2 as a molecular window into speech and language concludes that, “Spoken language depends on motor control of vocal output and auditory processing of speech signals. In species that learn complex vocalizations through imitation, auditory processing and motor control must integrate. The relevant neural underpinnings can be assessed in animals and could be similar in humans. But what of the essence of language: grammar, abstraction, meaning, thoughts? There is no evidence so far that animals that communicate vocally use language-like grammar systems to refer to objects or actions. However, it is an immense challenge to search for rule systems in complex streams of vocalizations in animals with large sound repertoires; this kind of effort has yet to be carried out on an adequate scale. Even if such rules were deciphered, we would still have the problem put forward by [the philosopher Ludwig] Wittgenstein, ‘If a lion could speak, we would not understand him’.”

While the role of FOXP2 expression in the evolution of human language is unclear, it does appear to be an important developmental factor for speech creation and learned vocal communication. But, its role in the processing of higher-order linguistic elements, like syntax and semantics, is not well-defined. The gene being identical in modern and archaic humans may imply that they too had complex language, but finding non-molecular evidence to support this hypothesis has proven difficult. How does one determine the presence and complexity of language from archeological specimens, barring evidence of actual writing? Archeologists posit that a requisite for language is the cognitive capacity for symbolism. Indeed, as Ferdinand de Saussure (one of the founding fathers of modern linguistics) asserted, words are merely symbolic representations of mental concepts. Evidence for this kind of symbolic thought may be found in the practice of burying the dead. “This act […] represents a consciousness and awareness of self or one’s species as distinct from the natural world. With the practice of burial, the body has become a symbol of identity with the species.” And most anthropologists now agree that archaic humans did at least occasionally bury their dead. Another piece of evidence linked to symbolic cognition is ornamentation, and “findings show they [also] likely decorated themselves using pigments, and wore jewelry made of feathers and colored shells.”

In the end, can we confidently assert that language is the unique and defining driving factor in the expansion and global dominance of Homo sapiens if archaic humans like Neanderthal possessed it as well, but never managed to exist in anything but small, fragmented populations before being driven to extinction? Can we point to language as the singular trait that bolsters the human claim to “dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth” if we have evidence of its presence in at least a basic form among other species? Astronomical assertions of human exceptionalism – that our planet’s position is central to the solar system and the universe – have long been proven false. And our discovery of the evolutionary process has revealed that the difference between humans and other animals is one of degree, not kind. Given the historical evidence, I am inclined to err on the side of caution.