Softer Diets Allowed Early Humans to Pronounce “F,” “V” Sounds

In 1985, the American linguist Charles Hockett proposed a radical idea during a lecture at the annual meeting of the American Anthropological Association: “f” and “v” sounds only became part of spoken language after the dawn of agriculture, and as such, were a “relatively recent innovation in human history.”
Hockett reasoned that softer, processed foods would lead to changes in the arrangement of the human bite, making the pronunciation of these sounds possible. This would explain why many hunter societies don’t tend to use “f” and “v” sounds in their languages. But the idea was sharply criticized, and Hockett himself soon gave up on it.

A new look at old ideas
Now, more than 30 years later, an international team of researchers has taken another look at Hockett’s hypothesis. This time they used information from historical linguistics and paleoanthropology data and combined it with biomechanical simulations of sound production.
In particular, they studied labio-dental sounds: these require the require the involvement of the bottom lip and the upper teeth. They concluded that such sounds only emerged recently (last few thousand years) because the human diet changed, and with that, the human bite as well. The research was published in the Journal Science.
“Hockett’s paper was always just a curiosity to me, but now this is something I’ll talk about in class,” remarks Joe Salmons, a professor of language sciences at the University of Wisconsin who wasn’t involved in the study. “Whether they’re ultimately right or not, we can’t say for sure. But it’s a much more powerful case.”

Bite-sizes
Modern-day humans start out as children with the same bite configuration as young hunter-gatherers did thousands of years ago. They have an “overbite,” in which the upper jaw overlaps the lower one, and an “overjet,” where the top front teeth protrude over the bottom ones. In previous studies, this bite configuration has been shown to change depending on the diet.
To investigate if this were true, the researchers simulated the production of a labio-dental sound using computers. Since they modelled the mechanical working of the oral cavity and the facial muscles, it is called orofacial mechanics.  Energetically speaking, making “f” and “v” sounds with an overjet and overbite is nearly 30 percent more efficient than with an edge-to-edge bite.
Through statistical techniques, they examined the relationship between the distribution of labio-dental sounds across nearly 2,000 languages worldwide and their speakers’ sources of food. The biggest contrast is expected to be in hunter-gatherer societies where the food is mostly in raw or un-processed state, and in food-producing societies where sophisticated processing methods are used. For instance, the meat eaten by hunter-gatherers is more rough on the teeth while the processed soft foods that we eat in cities hardly requires chewing. They found that, on average, hunter-gatherer societies have only 27 percent as many labio-dental sounds in their vocabulary as do food-producing societies.

Hunter gatherers and sounds
The researchers also looked specifically at several regions with a history of hunting and gathering until very recently: Greenland, southern Africa, and Australia.  Many native societies in these areas don’t express labio-dentals (that is, do not have such sounds), but some have picked up these sounds through contact with groups who do use labio-dentals. For instance, the language of West Greenlandic has acquired one labio-dental sound. This was probably due to long contact with Europeans since the 18th century.
“The diet came with these people that [also] provided them with the words,” says Damián Blasi, a postdoc at the University of Zurich’s Psycholinguistics Laboratory and first author on the study.

Phylogenetic Analysis
Phylogenetics is the study of evolutionary relationships among biological entities - species, individuals or genes.  Researchers reconstructed the evolution of labio-dental sounds through a phylogenetic analysis of the Indo-European language family. According to the model, labio-dental sounds most likely emerged between 3,500 and 6,000 years ago across different languages, coinciding broadly with archaeological evidence of bite configurations. For instance, human skulls from Pakistan show evidence of an overbite and overjet around 4,300 years ago. The model suggests a particularly steep rise in the use of labio-dentals some 2,500 years ago, around the time when industrial milling of food became widespread in western Europe.
Blasi says he and his colleagues were initially surprised at how well the different lines of evidence supported Hockett’s theory. However, he cautions that maintaining an overbite and overjet doesn’t necessarily guarantee that a particular community will start using labio-dentals in speech, it just means there’s a higher probability they will. There are plenty of exceptions to the rule: Spanish, for instance, has an “f,” but no spoken “v” he notes: Most varieties of Spanish pronounce the letter “v” as a “b,” a sound which is produced through both lips. Plus, there are many other factors that determine whether a sound will be acquired in a given language. Perhaps some sounds carry a negative social connotation, or others aren’t easily audible. “There’s so many things we don’t know about the dynamics of language.”
Pedro Tiago Martins is a graduate student at the University of Barcelona. He studies the evolution of speech. People used to believe that humans can make a range of sounds that has remained the same over ages. Now he has shown that “the sound system we have is not fixed,” and can be shaped by the environment and culture.
Cultural changes, such as the agricultural revolution, can affect biology and vice versa, points out Timothy Weaver, a biological anthropologist at University of California, Davis. The new findings provide a good example: “You have these cultural changes that lead to dietary changes and those dietary changes influence the anatomy, and the anatomy then influences an aspect of culture, that is, language.”
Salmons is particularly impressed by the variety of evidence the researchers provided, and says he hopes the study will raise the bar for future work on the effect of the environment on language evolution.  “I really like that they used such a multi-faceted approach for this kind of question,” he says. “No single strand of evidence alone would have made the story the way that the whole set does.”