We still know embarrassingly little about the origin of perhaps the most important evolutionary product for our species – natural language.
Communication is a widespread phenomenon in the animal world, occurring across the entire “tree of life” – and it takes many forms. It can be expressed through gestures (e.g., in great apes), sequences of movements (like birds’ courtship rituals), scents (pheromones released by insects), sounds (e.g., frogs croaking), changes in body coloration (as in cuttlefish), bioluminescence (light emission – as in fireflies or deep-sea fish), facial expressions (including eye gaze), and even vibrations traveling through water, soil, leaves, or spider webs. Naturally, many species use several modes and channels of communication, each with its own evolutionary story.
In the broadest sense, we speak of communication when a message is sent from a sender to a receiver – though the sender doesn’t always act intentionally or even know the receiver is present. Signals can be sent involuntarily, triggered by environmental stimuli or emotional states. Most animal communication seems to work like this. And it’s not too surprising, since the vast majority of animal signals are alarm calls (warnings about predators), mating calls (like birdsong), territorial threats (like the duets of gibbons), or signals about food sources (like the famous bee dance). Each of these messages has a specific environmental or emotional context. This type of communication isn’t flexible – an animal can’t send a message without the appropriate context – nor can it express arbitrary content. The advantage? It requires little cognitive effort – natural selection could hardwire it even into creatures we’d hardly call intentional or conscious.
The meanings of such messages are typically hardwired genetically, and animals don’t need to learn them (though some do – for example, impalas, zebras, and wildebeests have been shown to understand alarm calls not only from their own species but from the others as well).
A Lack of Continuity?
Human natural language stands out against this backdrop: it’s highly flexible, it allows us to convey virtually any content (even fictional or absurd), it’s symbolic (we must learn the meanings of words – they’re not inborn), and above all – we generally use it intentionally.
With many human anatomical traits, practices, and behaviors, we can speak of evolutionary continuity. Take bipedal posture or tool use – once thought to define humanity; the fossil record shows how they evolved in our ancestors. Related species show similar traits (great apes can walk on two legs, though not for long distances; many monkeys use tools, like stones to crack nuts). But language seems trickier – for a long time, researchers believed no form of animal communication resembled human language enough to qualify as an evolutionary precursor. The fossil record is little help – since words and gestures don’t fossilize, we’re left with indirect clues, like social complexity or geographic spread of hominid species.
Daniel Everett, for instance, argues that Homo erectus (who emerged about 2 million years ago and went extinct 100,000 years ago) must have used language – they built campsites with clear divisions of labor: areas for resting, meat processing, and plant processing. They also reached distant islands (like Crete), suggesting knowledge of seafaring. According to Everett, achieving all this without advanced language would’ve been impossible.
No Consensus
Back to great apes: psychologist Michael Tomasello believes they have a rich repertoire of vocalizations (e.g., when spotting predators, encountering threats, or finding food), but their use is not flexible. Apes vocalize more or less unconsciously. Hence, it’s hard to see these calls as the evolutionary roots of human words. Tomasello argues that gesture-based communication came first – something between pantomime and modern sign language – and this form paved the way for the development of brain circuits later adapted for processing speech, which he views as a cultural invention. In support of this, apes sometimes use gestures intentionally: to get someone’s attention (e.g., by slapping the ground or throwing a stone) or to express intention (e.g., pulling another individual’s arm in the direction they want to go).
However, recent years have brought new discoveries in the realm of natural primate communication. Thanks to research in “primate linguistics” – applying methods of traditional linguistics to primate vocalizations – we now know that primate vocal communication is more complex than previously thought. Playback experiments have shown that the meaning of vocalizations can be modified by syntax; each call can be broken into components (syllables), and changing their order affects the listener’s response.
We also know that apes possess a theory of mind – meaning they perceive others as intentional beings, worth communicating with deliberately. Overall, vocalizations seem to play a more central role in their lives than gestures. Therefore, more and more scholars today argue that we shouldn’t look only to ape gestures for the roots of our own language – primate vocalizations must also be part of the story.
Still, we must remember: we’re only just beginning the journey. Solving one of the great mysteries of science will require more discoveries – not only in animal communication, but also in paleoanthropology and neurobiology.
Łukasz Kwiatek