Why Do We Have Crooked Teeth When Our Ancestors Didn’t

The Mystery of Ancient Skulls with Perfectly Straight Teeth

Upon examining ancient skulls, one striking feature is their perfectly straight teeth. This is not an anomaly, but a consistent trait found in the fossil record of ancient humans. They typically had straight teeth, including third molars or wisdom teeth. This is in stark contrast to the modern human condition where dental issues such as crooked teeth and impacted wisdom teeth are common. So, what happened to cause this shift?

The Hypothesis: A Shift in Lifestyle and Diet

While it’s difficult to pinpoint the exact cause, scientists have a hypothesis. A couple of million years ago, the ancestors of modern humans lived a subsistence lifestyle. Their teeth and jaws had to work hard to make their food digestible. This is evident from the extensive wear and flattening seen on the surfaces of their teeth. They also had larger jaws and teeth overall.

Over time, these early humans began using tools and fire to cook and prepare food, which helped break it down. Around 12,000 years ago, some humans started farming and domesticating animals and plants. Over several thousand years, it became more common for people to process and refine their food. Milling technologies helped remove the tougher parts of grains, like the germ and bran from rice and wheat.

The Industrial Revolution and Its Impact on Dental Health

Fast forward to the Industrial Revolution, and technological innovations dramatically accelerated these processes. In a relatively short time, many human mouths were relieved of their grinding, crushing, and pulverizing duties. Interestingly, it was around this time that tooth crookedness appears to have become more common.

Examining fossils spanning millions of years of evolution, researchers have observed a gradual decrease in tooth and jaw size in humans and our ancestors. Many believe that for most of human history, dietary shifts, like the introduction of meat and the advent of cooking, were gradual, and changes in tooth and jaw size basically kept pace with one another. But with the more recent revolutions in agricultural and culinary habits, that relationship changed.

The Theory: Decreased Jawbone Size and Dental Crowding

As the theory goes, over a relatively short period, some human populations saw a decrease in jawbone size, while teeth stayed roughly the same size. This meant that teeth were left vying for limited space. When they did grow in, they may displace others and get jostled into some eccentric positions. Wisdom teeth, which are usually the last to make their debut, seem to only complicate things further. In many cases, they have little or no space to emerge, leading to impacted wisdom teeth, which may cause discomfort and infections if not surgically removed.

So, larger jaws appear to be associated with greater chewing demands. Many scientists think that as people’s diets have become less chewy, their jaws have gotten smaller, leading to dental crowding, resulting in dental crookedness and impacted wisdom teeth.

Supporting Studies and Global Variations

This hypothesis has been supported by some preliminary experimental data. For instance, a 1983 study found that squirrel monkeys raised on diets of softer food had more crowded premolars, rotated or displaced teeth, and narrower dental arches. A 2004 study similarly observed that hyraxes raised on cooked foods experienced roughly 10% less growth in facial areas involved in chewing compared to those given raw and dried foods.

It’s estimated that somewhere between 30 to 60% of people today experience some level of tooth crowding. However, this trend varies across global populations. Some people naturally never have wisdom teeth. Some don’t experience tooth crowding or crookedness and still get their wisdom teeth without a hitch. This seems to coincide with diets that are less processed.

Preventing Tooth Crowding: Lifestyle Changes and Orthodontics

So, how can we prevent tooth crowding early, using lifestyle changes and orthodontics? Well, it’s certainly something to chew over. The issue at large seems to be environmental or one of lifestyle, instead of a genetic one, though heritable factors may be at play in some instances.