"French fries" may not be on the menu, if not for old farmers, and not because we can now grow a lot of potatoes, but because it would be harder to say them them. The ability to make labiodental sounds – which are sounds that require you to put your lips on your upper teeth, like f and v sounds – may not have evolved into since agriculture introduced softer foods to the human diet, our jaws changed, according to an exciting and controversial study published today in Science.
Orthodontists know that overbite and the jaw's horizontal overlap is called overjet, are common among people all over the world. But the study's authors claim that such jaw structures were rare during the Paleolithic Period, when the hunter-gatherer rough diets demanded more force from teeth that faced the edge. Agriculture softened our ancestors' diets with processed gruel, stews and yogurt, and this fare led to gradually shrinking the lower jaws to produce today's overflowing mouths. This diet-driven development of the human bit over the past 1
The university hospital in Zurich's linguists Balthasar Bickel suggests that less wear and stress on teeth and jaws can be overstated to continue more often creating a closeness between the upper teeth and the lower lip which made it a little easier to release f and ] v sounds. (Try to make a "fuh" sound, first with your upper and lower toothed edge to edge and then, probably more successfully, with your lower jaw retracted so your lip can easily touch your upper teeth.)
One of the home messages is really that the landscape of sounds we have is fundamentally influenced by our speech therapist's biology, Bickel said at a press conference this week. "It's not just cultural development".
Every time old people talked, it was only a small chance that their slowly growing jaw configurations produce labiodental sounds, but as a genetic mutation, it could have been caught over time. "Every statement you make is a single trial. And if you think of what is going on for generations over generations, you have thousands and thousands of attempts – with this probability always changing – leaving the statistical signal we find in the end," Bickel
Bickel and colleagues tested the idea that overbite helped to produce labiodental by building biomechanical models and getting them to talk, their data suggesting that f and v sounds 29 percent less muscular effort when the speaker has an overbite / overjet configuration, the researchers then searched for probable evidence of where laboratory signals became more common over time.
"We looked at the distribution of labiodental sounds across thousands of languages and their relationship to the characteristic sources to human food that speaks these languages, "Damián Blasi, also at the University of Zurich, said at press conference The study showed that languages spoken by modern hunter-gatherers only use about a quarter as many labiodental as other languages.
Tecumseh Fitch, an expert on bioacoustics and language development at the University of Vienna who was not involved in the new study, says the multidisciplinary approach biomechanics, bioacoustics, comparative and historical linguistics came to him as a surprise. "This is probably the most compelling study and yet shows how biological limitations to language change can change over time due to cultural change," he says via e-mail. "The survey inevitably builds on various assumptions and reconstructions of unknown factors (especially bite structure in current and ancient populations), but I believe the authors are building a very likely case that will open the door to future detailed research."
Yet, the evolutionary process remains far from clear. Despite today's ubiquitous modern dental orientations around the world, half of about 7,000 existing languages never began to use regular sounds at all. And the correlation between sounds and softer food does not always keep up. Cooking has been around for hundreds of thousands of years, which facilitates the stress on human teeth and jaws. The ancient Chinese farming produced light-chewing rice, but and v sounds are not as common in Chinese as they are in Germanic or Romance languages.
Bickel, Blasi and colleagues argue that the development of overbite only meant labiodentales would be produced more often. "It does not mean that labiodentals will show up in all languages. This means that the likelihood of producing labiodes is increasing slightly over time, and that means some languages will acquire them, but not all languages will come," co-author Steven Moran says.
Not everyone is convinced that the diet transformed our tooth adjustment primarily, however. "They haven't determined that a soft diet would give you an overbeat," said Philip Lieberman, a cognitive researcher at Brown University. "To relate it to diet, it must be epigenetic," meaning that chemical compounds that become bound to genes can alter gene activity without altering the DNA sequence. "There must be some sort of regulatory mechanism triggered directly from the environment or diet, and I do not know about any data on an epigenetic remodeling [tooth and jaw position]." Such a link would not convince Lieberman that change led to the rise of f and v sounds. "We can produce these sounds if we have overbid or not," he says. "There is arbitrary language. People have different words for the same things, and I don't think we can relate any of it to changes in the teeth."
Evolutionary biologist Mark Pagel at the University of Reading found some of the authors' suggestions more credible. "If their argument that the overbite or exaggerated has become more prominent in the latest fossils, it is indeed true, if you get a developmental change that actually changes the shape of our mouths, then there is a real plausibility for it," he says and adds. these sounds tend to develop through the least resistant path. "We make the sounds that are easier to do easier. We are constantly introducing small variations. And if the shape of your mouth means that you are more likely to introduce some kind of variant … then they are just a little more likely to touch . "
Despite the correlation between mouth shape and sound, paleo anthropologist Rick Potts of Smithsonian's Human Origins Program, reservations about the study's conclusion have been that altered diets caused an increase in labiodentals. "In my opinion, they do not provide sufficient reasons why we include diet as the cause of producing and f sounds because they are not at all about the anatomy of producing them sounds."  and f sound, Potts requires, only a very slight retraction of the temporal muscle on the side of the head that pulls the jaw backwards with a very subtle movement. "How does a harder diet limit the direction of the jaw?" Asking him. "It is the essence of being able to make v and f sounds, in no way showing how a chewing-to-bit configuration of the teeth inhibits or makes it more expensive to make these sounds "I can't see anything in how the teeth are oriented towards each other that would restrict the jaw retraction." Potts says the study identifies some exciting correlations but lacks short evidence of causality. As an example, he says that if scientists found that coloreds were favored by equatorial populations like Masai and they also found that such people had a lower density of light receptors in their retinas than arctic people, they could conclude that the lack of light receptors was a biological cause for to prefer color red.
"But how would you discount the fact that only cultural history is why Masai carries red while Arctic people tend not to?" Asking him. "It is just as people separate themselves and it is forwarded in ways that are geographically oriented. I am only concerned that [the study] has not received enough credit for the idea of cultural history and identity accidents as part of why v and sounds are less frequent in some groups of people around the world than others. "In contrast, Balthasar Bickel says that the language has often been considered a purely cultural or intellectual phenomenon and hopes that his group work will help to open new scientific lines of inquiry. "I think there is a great potential out there to study languages as part of the biological system it really is embedded in."