As many dentists know, overbites are rather commonplace today. However, even the dental profession’s keenest historians may be unaware that our Stone Age ancestors once sported much straighter smiles, with top and bottom teeth that didn’t overlap. And only recently have researchers begun to consider why overbites are currently so prevalent.
The theory of evolution was famously outlined by British naturalist Charles Darwin in his epochal 1859 work On the Origin of Species. In the book, Darwin suggested that life forms change over long periods of time as a result of natural selection. And owing to this process, organisms that are well adapted to their environments live for longer and pass on more of their genetic traits to the next generation than those that fail to acclimatize to their surroundings.
Eventually, then, and with enough changes, natural selection is able to create a whole new species. This process is called macroevolution, and it’s thought to be responsible for a number of animals that we know today. Yes, macroevolution is said to have been key in creating birds from dinosaurs, whales from amphibious mammals and humans from ancient apes.
Scientists agree, for example, that one of the major traits separating early humans from other apes was walking on two feet, with this development believed to have occurred over four million years ago. However, early human species still retained the physical characteristics associated with tree dwellers, including arms that were longer than their legs and arched toes and fingers.
And it wasn’t until Homo erectus came into being nearly two million years ago that our ancestors became completely upright. What’s more, this particular quality – known as bipedalism – is thought to have greatly impacted human evolution. With free use of their hands, early humans could now use weapons and tools; they could also take resources from trees and carry food and infants over long distances.
All things considered, then, it’s easy to see that learning to walk on two legs has been largely advantageous to our species. However, the benefits of many of our other evolutionary quirks are far less obvious. For instance, why did our ancient ancestors first begin to develop overbites, and for what purpose?
Well, it’s worth noting that while teeth may feel firmly secured in our jaws, they are actually quite movable – as those who have had to wear braces may know. Furthermore, as we age, our teeth tend to drift quite a bit. So, while an individual may be born with an overbite, this can naturally correct itself. As the teeth begin to see wear through use, you see, the bottom jaw may compensate by moving forward – thus making the choppers more closely aligned.
And for the first part of human history, upper and lower tooth-edge alignment was typical in adulthood. We know this as it is evident in ancient skulls that have been studied over the last 30 years. However, thanks to a shift in diet, overbites gradually became more of a prevalent feature in human adults.
Yes, after humans came to use new agricultural techniques – including the domestication of livestock and the growing of grains – thousands of years ago, their diets changed dramatically. Softer foods then began to dominate eating habits, meaning teeth took longer to wear down. And as a result, a greater number of people maintained overbites into later life.
However, prior to the introduction of agriculture approximately 10,000 years ago, humans relied on what’s commonly known as a hunter-gatherer diet. And before our ancestors started cooking their food, this often meant chomping through raw meat and veggies – with all that extra work likely taking a toll on their jaws and teeth.
Then new farming methods introduced milk into early humans’ diets, which our ancestors could later store in newly developed pots. The fermentation process, moreover, created yogurt and soft cheese. And further advancements in milling meant that our predecessors could make softer bread than ever before.
Gradually, diets therefore shifted from tough foods to softer ones with the addition of meals such as porridge, gruel and stews. And this took some of the chewing pressure off humans’ teeth, changing the position of their jawlines. Consequently, over time, overbites became much more common – even in adults.
So, owing to these changes in diet, Stone Age skulls often differ from those of modern humans – not least because they typically show lower and upper teeth aligning neatly on top of each other. By contrast, overbites – or top teeth extending over and in front of the bottom teeth when the jaw is placed together – are often seen in people today.
Balthasar Bickel, a linguist at Switzerland’s University of Zurich, has spent time studying the evolution of the human jawline. And in March 2019 he explained how overbites became more prevalent while talking to the Daily Mail. “If you are raised on softer foods, you don’t have the same kind of wear and tear on your bite that your ancestors had. So you keep an overbite,” Bickel said.
And thanks to overbites, human communication may also have evolved. You see, while languages change and develop according to different societies, the way an individual speaks depends on the position of their jawline. As softer food allowed for overlapping teeth, then, our ancestors may have been able to make some different sounds with their mouths.
In particular, early humans were eventually able to pronounce the letters “v” and “f,” which in turn are now thought to be relatively recent additions to our collective lexicon. And this revelation was made by Bickel, who co-authored a study that investigated how biological factors have affected the way we speak.
In the past, linguists have focused more on cultural factors when studying the origins of language. However, Bickel and his team of researchers at the University of Zurich compared modern skulls with their Stone-Age counterparts, creating simulations to determine how differing jaw placements affected the sounds that humans would have been able to make.
Alongside this work, the scientists also researched an estimated 2,000 languages – over a quarter of those spoken on the planet today. And by analyzing these dialects, the team could therefore determine which sounds appeared regularly and where they were most common.
Consequently, the researchers found that the languages spoken in societies that were hunter-gatherers until more recently used fewer consonants than groups that have been agricultural for a long time. In turn, this revelation provided them with evidence that biology may well have an effect on the ways in which we speak.
And State University of New York at Buffalo evolutionary anthropologist Noreen von Cramon-Taubadel explained these findings in layman’s terms to the Daily Mail, although she wasn’t involved in Bickel’s study. “Our anatomy actually changed the types of sounds being incorporated into languages,” she said.
Bickel seemed to agree with von Cramon-Taubadel’s conclusion, too. Summing up the findings of his study in a statement obtained by the Daily Mail, he simply said, “Our work shows that language is also a biological phenomenon. You can’t fully separate culture and biology.”
All in all, then, it appeared that a diet consisting of softer foods had set the jaw in such a fashion that it was subsequently a lot easier to say “v” and “f.” Try pronouncing the word “favor” with your teeth edge-to-edge aligned, and you’ll find that it’s not that easy to express what linguists would call the “labiodental” sounds.
So, while changes in the makeup of our mouths didn’t guarantee language alteration, researchers believe that overbites made the pronunciation of “v” and “f” more attainable. These particular sounds are made by placing your bottom lip on the tips of the front teeth, and this position should be easier to achieve if the top teeth stick out a little more than the bottom ones.
In the study, meanwhile, Bikel’s researchers paid particular attention to 52 Indo-European languages. These included dialects from as far apart geographically as India and Iceland. And what the linguists were most interested in was how the use of labiodental sounds had increased in certain tongues over long periods.
Ultimately, then, the researchers found that languages spoken in modern hunter-gatherer societies use significantly fewer “f” sounds than those used by modern agricultural societies – four times fewer, in fact. And as a result, it’s possible that the prevalence of labiodental sounds are linked to diet.
Furthermore, it appears that “v” and “f” sounds only rose to prominence in Europe 2,000 years ago. To put that into perspective, Roman Emperor Julius Caesar died prior to that timescale, in 44 BC, meaning his famous “Veni, vidi, vici” speech may have actually sounded a bit different to how we now imagine.
And Dr. Steven Moran – the study’s co-author and Bickel’s colleague at the University of Zurich – spoke to the Daily Mail about the issue. He explained, “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.”
Moran added, “The influence of biological conditions on the development of sounds has so far been underestimated.” And Bickel apparently agreed. The linguist told National Geographic in March 2019, “The landscape of sounds that we have is fundamentally affected by the biology of our speech apparatus. It’s not just cultural evolution.”
According to the study, it seemed likely that labiodental sounds began to increase in prominence after particular cultures began to eat softer foods. Then, over time, they spread through populations. “New sounds get introduced into languages and then are more widely adopted,” Moran explained to the Daily Mail.
But it’s worth noting that the University of Zurich team aren’t the only ones to have advocated such a theory. In a 1985 essay, Charles F. Hockett also suggested that agricultural advances had allowed for pronunciation of labiodental sounds, with the American linguist basing this supposition on a claim that had been made by anthropologist C. Loring Brace. However, the year after Hockett’s essay appeared, Brace withdrew his assertion – causing Hockett to throw his idea out, too.
And for years, Hockett and Brace’s dismissals were taken as a conclusion on the matter. Yet when the University of Zurich team came to reexamine the issue, they realized that the men may well have been on to a good thing after all. “We tried for months to show that this correlation didn’t exist … And then we thought [that] maybe there’s actually something there,” Moran revealed to National Geographic.
With that in mind, Moran and his team created computer-generated models to replicate the muscles and bones in the face. From there, they went on to analyze jaws with and without overbites. And as a consequence, the researchers found that those without an overbite use nearly 30 percent more energy when producing labiodental sounds. They concluded, then, that overbites made “v” and “f” much easier to pronounce.
One theory suggests that the first “v” and “f” sounds may have appeared accidentally. Perhaps they came about when people mispronounced bilabial sounds – which are made when both lips touch – such as “b” and “p.” However, these new noises seemed to have stuck, as they were later adopted into languages.
And if confirmed, the results of the research would be some of the first to prove that a change in human biology – itself caused by cultural factors – could influence global language. This potential development may therefore have consequences for linguists, according to Damián Blasi, who was a lead author on the University of Zurich study.
In March 2019 Blasi told National Geographic, “I hope our study will trigger a wider discussion on the fact that at least some aspects of language and speech – and, I insist, some — need to be treated as we treat other complex human behaviors.” By that, he meant that their influences exist somewhere “between biology and culture.”
And William Tecumseh Fitch, a bioacoustic expert from the University of Vienna in Austria, seemed to be won over by Blasi and his colleagues’ work. “I think the authors build a very plausible case,” he told National Geographic. “This is probably the most convincing study yet showing how biological constraints on language change could themselves change over time due to cultural changes.”
Not all linguists were so impressed by the results of the University of Zurich research, however. The University of Southern California’s Khalil Iskarous, for example, seemingly had some reservations in advancing the theory that the prevalence of labiodental sounds can be solely chalked up to overbites making them easier to produce.
If this was the case, Iskarous argued, sounds that were harder to produce with an overbite – like the aforementioned bilabials – would have likely fallen out of fashion. Furthermore, he was doubtful that energy expenditure played any real role in the evolution of language.
Pointing to the use of clicks in some southern African languages, Iskarous told National Geographic, “If extremely small amounts of effort make a difference between whether you’re likely to have a speech sound or not, you would predict, for instance, that no language should have clicks. And clicks not only exist, [but] they’ve [also] spread into many languages that didn’t have them.”
So, the jury is still out among linguists when it comes to determining the effect that overbites have had on the world’s languages. However, it would be amazing to think that an evolutionary process such as tooth erosion – or the lack thereof – could actually have influenced the way we speak. And it’s no less incredible to realize that the position of our jaws may actually be down to a change in our ancestors’ diets thousands of years ago.