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Softer foods from agricultural lifestyles may have changed the human bite, making it easier to form certain sounds.
Thousands of years ago, some of our ancestors left behind the hunter-gatherer lifestyle and started to settle down. They grew vegetables and grains for stews or porridge, kept cows for milk and turned it into cheese, and shaped clay into storage pots.
Had they not done those things, would we speak the languages and make the sounds that we now hear today? Probably not, suggests a study published Thursday in Science.
“Certain sounds like these ‘f’ sounds are recent, and we can say with fairly good confidence that 20,000 or 100,000 years ago, these sounds just simply didn’t exist,” said Balthasar Bickel, a linguist at the University of Zurich and an author of the new research.
The study concluded that the transition to eating softer foods changed how bites developed as people aged. The physical changes, the authors said, made it slightly easier for farmers to make certain sounds, like “f” and “v.”
Through various other processes that the study did not directly address, these sounds made their way into about half the languages used today. The study’s authors called for greater consideration of biological factors in studying the development of human language.
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A number of linguists agreed that the findings are plausible, but others said the study’s broader conclusions about agriculture’s effect on language may be overstated. Some cautioned against interpretations that may unwittingly restate discredited ethnocentric or racist views that in the past have tarred the study of linguistics.
Dr. Bickel and his colleagues revisited a question about the origins of language: Were some of the diverse sounds we hear today acquired only recently? While most linguists think language abilities are universal and haven’t really changed over the course of human history, the new study suggested that over the past few thousand years, agriculture fostered the arrival of new sounds in human voices.
In 1985, a linguist named Charles Hockett observed that “f” and “v” sounds appeared less frequently or were absent in the languages of some hunter-gatherers. He proposed that dietary changes, promoted by the spread of agriculture, may have transformed teeth and jaws, making it easier for people to produce some sounds and more difficult to articulate others.
But many criticized Dr. Hockett’s idea, which he ultimately abandoned — and that was even before linguists began favoring the brain’s role in guiding language over social or physical influences.
In the time since, however, researchers learned that through gradual processes, diet may shape human bite. But the connection to sounds we make remained unclear.
In the new study, researchers pored over thousands of languages. With computer simulations of differently shaped mouths and other techniques gathered from paleoanthropology, linguistics, speech science and evolutionary biology, the scientists found that eating softer foods, associated with agriculture, changed adult bites.
For those living on a hunter-gatherer diet, overbites in the jaws and teeth in youth were often replaced in adulthood by what are called edge-to-edge bites, where front teeth sit atop one another. But with a softer diet, overbites may persist into adulthood.
With an overbite, pronouncing sounds called labiodentals, which require moving the bottom lip against the top teeth — think of the words “fava” or “fever” — is about 30 percent easier. Over thousands of years, more of these sounds could have made their way into language.
This scenario is more probable than not, the researchers said, although they concede it may not occur universally. “Some languages will develop labiodentals,” said Steven Moran, a linguist at the University of Zurich. “Some languages don’t.”
The findings challenge the idea that the sounds we make are more related to human evolution and how it shaped our brains, a subject the paper doesn’t dwell on.
Our hominin ancestors may have cooked food, for example, which made it softer. That contributed to changes in the shape of the skull and mandible, which made way for a more complex brain long before agriculture influenced diet, said Jordi Marcé-Nogué, who studies jaw evolution in primates at the University of Hamburg in Germany.
“What came first?” he asked. “The changes in the speech, or the changes in the brain?”
Ray Jackendoff, a linguist at Tufts University who was not involved in the study, said the group’s finding that the ease of saying some sounds may vary with diet “is interesting but not earthshaking.” That different cultures may have uttered certain sounds more often than others “doesn’t say much about the deep history of language.”
Other cultural and social factors, like adopting sounds from neighbors, also may have contributed to changes in language, the study’s authors said. For example, when hunter-gatherer groups and agrarian groups mixed, so did their sounds.
And others point out that labiodental sounds have even been found among hunter-gatherers with edge-to-edge bites, like some Yanomami people of South America, who live mostly as isolated hunter-gatherers, fishers and horticulturists.
Other linguists also point out that the study rests on untested assumptions, like just how much these small bite changes might influence sounds, the types of errors they could produce, the age at which hunter-gathers’ teeth wear down, and the notion that agriculture is a useful proxy for diet. The role of cognitive factors, including neural control of speech organs, also goes unaddressed.
The authors respond that they are not minimizing the roles played by culture, society or cognition in the development of language. But they say that physical differences between people deserve as much attention in the study of human language development as they do in research into the communication systems of animals.
Some linguists worry that if not handled with extreme care, subsequent studies of the physical or biological differences of language could invigorate ethnocentric beliefs that have plagued linguistics in the past, especially if research is publicly interpreted as making value judgments of different groups’ languages.
“The risk here is a bias to focus on positive benefits or what is gained by individuals in agrarian societies, rather than also considering whatever benefits individuals in hunter-gatherer societies might have,” said Adam Albright, a linguist at M.I.T.
Dr. Albright said the current study considered those questions, and he hopes that future inquiries in this area will also investigate what sounds might have been left behind in the shift to agriculture.
Dr. Bickel agreed: “It will be just as interesting to investigate which sounds might have gone lost with the transition to softer diets.”
Previous reporting on early farming and human development