Fossils hold many clues to human evolution. But the origins of human speech — there are about 6,000 spoken languages today — are less well-known. Muscles and organs leave behind no fossilized remains and so the evolution of language is harder to trace.

To piece together the puzzle of human speech, scientists have looked for evidence in several places, including ancient writings, the comparable vocal tracts in our primate relatives and in experiments based on anatomical and acoustical models.

About 50 years ago, scientists arranging these puzzle pieces began to hypothesize that the clues to human speech lay in the shape and position of the human voice box, or larynx. It’s lower in the throat in modern humans than it is in apes and monkeys. The scientists named their theory the laryngeal descent theory of vowel production, according to The Atlantic. If correct, the theory means that modern Homo sapiens developed the vocal tract for language somewhere between 200,000 and 300,000 years ago.

But the latest research on the evolution of language, published in 2019 in the journal Science Advances, pushes back on this long-held theory. It suggests that the evolution of the spoken word can be traced back 27 million years, to when humans and Old World monkeys, such as baboons and macaques, shared a common ancestor. In an editorial piece for The Conversation, scientific team leaders Thomas R. Sawallis, a visiting scholar at the University of Alabama, and Louis-Jean Boë, a senior researcher at the University of Grenoble in France, write that their finding, “frees researchers in speech, linguistics, primatology and human evolution from the laryngeal descent theory,” which means they can look for clues outside the confines of what has become linguistic dogma.

Incumbent Theory

Writing dates to around 3200 B.C., according to Discover, and it shows signs of words, sentences and grammar. Humans had, by then, a mature grasp of language. For clues to the spoken word, though, scientists have looked to primates, such as apes and monkeys, who are genetically related to humans. They’ve also used anatomical and acoustical modeling technology to calculate the kinds of sounds differently shaped vocal tracts can and cannot make, reports The Conversation.

From research in these areas came the widely accepted laryngeal descent theory of vowel production, attributed to Philip Lieberman, who is now a professor at Brown University. Not only does the theory focus on the shape and low position of the larynx in modern humans, it also takes into consideration a human’s throat cavity, which is longer than that in Old World monkeys, and our comparably shorter tongue, which curves down into the back of the throat. The theory says that these features give modern humans the ability to produce contrasting vowel and consonant sounds as well as syllables and syntax. It also purports to explain why other animals, who lack this anatomy, can’t make these sounds.

Around the same time that the low position of the larynx shows up in modern humans — between 200,000 and 300,000 years ago — they started making jewelry and cave paintings. They formed settlements and began farming. These archeological findings may be indirect evidence of the existence of the spoken word, scientists have argued. Language may have driven art, culture and cooperation.

The Challenger

Sawallis and Boë, whose multidisciplinary team has spent decades studying articulatory and acoustic modeling, child language research, paleontology, primatology and more offer several counterpoints in The Conversation. For starters, if other primates don’t have the anatomy to produce contrasting vowel sounds, they write, what explains the audio recordings from renowned primatologist, Jane Goodall, that show chimpanzees producing contrasting vowel sounds?

The scientists also point to 1,300 recorded baboon calls that they analyzed acoustically. Results showed that “the vowel quality of certain calls was equivalent to known human vowels.” The team says their research shows that by producing contrasting vowel sounds, apes and monkeys are indeed “talking” and were likely doing it 27 million years ago — not 200,000 years ago.

Some scientists, including Greg Hickok, a cognitive science professor at the University of California, Irvine who was not involved in the study, think the timeline is probably somewhere in the middle. He told The Atlantic that the ability to speak probably arose nearer to the time our ancestors split from genus Pan, which includes chimpanzees and bonobos — our closest living relatives. That occurred about 5 to 7 million years ago.

Future of Language

While linguists battle it out about the evolution of language, others are looking to the future. In April 2020, Andrew McKenzie, an associate professor of linguistics at the University of Kansas, and Jeffrey Punske, an assistant professor of linguistics at Southern Illinois University, published a study in the journal Acta Futura suggesting that interstellar travel will evolve human language beyond recognition. The journal captures technologies and ideas from the European Space Agency’s Advanced Concepts Team, which conducts science that’s strategically important to the agency’s long term planning — and interstellar space travel is certainly on the list.

At the core of their study is the fact that language naturally evolves over time. English speakers today wouldn’t understand someone who spoke Old English, which was used between the 5th and 11th centuries. And in more recent history, communities of people that have lived in close geographical proximity to one another but may have been separated by a mountain, for instance, spoke a totally different language. Switzerland is an excellent example. Depending on where a person grows up in this tiny country, they may speak German, French, Italian or Romansh as their native tongue.

Imagine then, an interstellar flight that takes not just years, but generations to reach its destination. “If you’re on this vessel for 10 generations, new concepts will emerge, new social issues will come up, and people will create ways of talking about them and these will become the vocabulary particular to the ship,” McKenzie said in a press statement. Even as language evolves on the ship, so too will it evolve on planet Earth, causing a wider division.

The scientists recommend that such crews include a linguist and an informed linguistic policy that helps the crew and its passengers adapt without having to refer back to Earth-based regulations.

Ironically, such a policy and a record of how the language changed onboard the ship could one day become a kind of fossil of human evolution.