Almost every child in Israel knows this sentence: “You need braces.” Millions of people around the world undergo orthodontic treatments, use braces, and even undergo jaw surgery – all for the perfect smile. But were crooked teeth always so common? A new study reveals that the answer is no.
When researchers examine ancient skulls, they discover a fascinating picture: Our ancient ancestors had broad and powerful jaws, with teeth that were naturally aligned. Although some cases of misaligned teeth were found among hunter-gatherers, this phenomenon was much rarer than it is today.
“The ancient skulls were astonishingly different from the structure of our faces,” explains Professor Julie Lawrence of the University of Nevada. “Ancient hunters had large, powerful jaws built for the hard chewing work of tough meat, fibrous vegetables, seeds, and nuts.”
About 12,000 years ago, a dramatic event changed the face of humanity – the agricultural revolution. As humans worldwide shifted from hunting and gathering to farming, their diet changed drastically. They began consuming more grains and processed agricultural products.
Over the years, with the introduction of processed food into our lives, the forces exerted on the jaws and teeth decreased significantly by about 50%, allowing smaller teeth to perform the chewing tasks that once required larger teeth.
For example, in the past people did not eat ice cream or white bread. When food is taken directly from the natural environment, it is likely a little grainier and rougher than things that have been cooked and processed.
The human jaw began to shrink over the years
The new food was softer, more processed, and required much less chewing. Over time, the mechanical effort on the jaw decreased, and over generations, the human jaw began to shrink – a trend clearly visible in the fossil record.
Professor Myra Laird of the School of Dental Medicine at the University of Pennsylvania explains: “If you don’t need a giant jaw, it’s energetically expensive to build that extra bone.” This shrinkage is, at least in part, an adaptive result of thousands of years of evolution.
But there is another aspect: Bone is very responsive to physical stress – even during a single lifetime. Less use of muscles leads to weaker bones. “If you switch to a liquid diet, you won’t use your muscles properly and you’ll see certain changes in the shape of your face,” explains Laird.
When the same number of teeth are crowded into a smaller jaw
What happens when you try to fit the same number of teeth into a smaller jaw? The answer: Crowding and crookedness.
“The way our teeth grow is like a zipper,” explains Lawrence. “The jaw moves forward and makes space for them to emerge.” If there is not enough room for the teeth to grow, they may become stuck or crowd together. Wisdom teeth, or third molars, are at particular risk of failing to erupt in jaws that are too small.
“This loss of space is basically what causes dental crowding and crooked growth,” says Laird. “The rate of misalignment has increased dramatically in modern humans, and it is common across all populations.”
But experts warn that the story is not so simple. Although crooked teeth appear more frequent in modern humans, crowding and impacted teeth were also observed in early hominid skulls.
The fossil record is limited and likely not fully representative. “Better teeth tend to preserve better,” says Lawrence, adding that anthropological data do not account for confusing factors such as missing teeth.
In addition, not all changes in tooth alignment can be attributed to diet. Extreme overbite or underbite, for example, results from the genetics of populations and is not related to industrialization.
Another factor in crooked teeth – the way we breathe. Various blockages and difficulty in nasal breathing unfortunately lead to mouth breathing, which contributes to the development of narrower dental arches and significant tooth crowding.
Many other factors can cause crooked teeth, including environmental conditions or developmental abnormalities. Certain populations are genetically more prone to misaligned teeth.
Ultimately, the prevalence of crooked teeth may also be due to an aesthetic bias. “Our modern society is much more sensitive to cosmetic issues,” says Herring. “I think we are much more aware of alignment problems now than anyone ever was in the past.”
The story of our crooked teeth is essentially the story of human civilization. The shift from primitive life to advanced society brought many advantages, but also a price – in this case, to our dental system.
Today, as we better understand the link between diet and facial structure, it is important to remember that despite evolutionary changes, we have modern tools to cope with the challenges. Today’s medical technology allows us to fix what evolution ‘ruined,’ and to maintain a healthy and beautiful smile.
The author, Dr. Eran Fermon, is a dentist and director of the Malo Clinic in Ramat Hasharon.