(CNN) - Although languages around the world vary greatly, some share similar speech sounds. A new study suggests that labiodental sounds like "f" and "v" are included in about half of the world's languages due to a change in our diet that relies on softer foods.
This contradicts the theory that the range of human sounds has remained unchanged since Homo sapiens emerged 300,000 years ago. The study was inspired by the hypothesis of linguist Charles Hockett, a leading figure in the field to help define linguistics as a science between the 1930s and the 1960s.
In 1985, Hockett proposed that hunter-gatherers would have had a hard time making "f" and "v" sounds because of their edge-to-edge bite, in which the teeth come together at the front of the mouth and meet evenly. Although they were born with an overbite, it evolved to an edge-to-edge bite due to the harder and tougher diet they consumed. So Hockett suggested that those labiodental consonants must have been a recent addition to human speech, appearing in conjunction with access to softer foods as people had the ability to mill grain.
An international group of scientists decided to test this hypothesis but include a broader approach by combining phonetics historical linguistics with biological anthropology. Their study was published in the journal Science on Thursday.
"There are dozens of superficial correlations involving language which are spurious, and linguistic behavior, such as pronunciation, doesn't fossilize," said Damián Blasi, study author and postdoctoral researcher in the University of Zurich's Comparative Linguistics Department, in a statement.
The researchers noticed that softer foods allowed modern humans to retain the juvenile overbite that once disappeared in adulthood, putting the upper teeth slightly in front of the lower teeth and allowing for labiodental sounds when the upper teeth touched the lower lip.
You can test this out for yourself by aligning your teeth edge to edge and trying to make an "f" sound, the researchers said. It's much more difficult.
"In Europe, our data suggests that the use of labiodentals has increased dramatically only in the last couple of millennia, correlated with the rise of food processing technology such as industrial milling," Steven Moran, study author and researcher in the Comparative Linguistics Department, said in a statement. "The influence of biological conditions on the development of sounds has so far been underestimated."
The researchers used biomechanical models replicating human speech and determined that labiodentals require about 30% less muscular effort in the overbite model compared with the edge to edge bite. They also found that labiodental sounds occurred accidentally when trying to make other speech sounds in the overbite model.
The study was focused only on labiodental sounds within the well-documented Indo-European language family that stretches from Iceland to the Indian state of Assam. This doesn't account for the wide range of "a" or "m" sounds, or even the clicking associated with some South African languages.
The researchers were also able to compare this to when food processing spread across the Indo-European area. The spread of pottery for preserving food, especially as agriculture was introduced, is also a key part of the softer foods diet.
And with the increase in diets rich in soft foods, labiodental sounds may spread even further, the researchers said.
"Our results shed light on complex causal links between cultural practices, human biology and language," Balthasar Bickel, project leader and University of Zurich professor of linguistics, said in a statement. "They also challenge the common assumption that, when it comes to language, the past sounds just like the present."
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