Why do we have crooked teeth when our ancestors didn’t?

All these ancient skulls boast flawlessly straight teeth, a remarkable sight considering they never had the luxury of orthodontic braces. And lest one thinks this is an oddity, the fossil record reveals that our ancestors typically exhibited well-aligned teeth, including the presence of third molars, or wisdom teeth. Surprisingly, the dental issues that drive the modern demand for braces and wisdom teeth extractions seem to be relatively recent phenomena.

So what caused this shift? While certainty eludes us, scientists have put forth a compelling hypothesis. Millennia ago, the ancestors of modern humans lived a subsistence lifestyle, necessitating their teeth and jaws to exert substantial effort in digesting their food. Evidence of extensive wear and flattening on many teeth surfaces supports this claim. Back then, larger jaws and teeth were the norm. With the advent of tools and fire, cooking and food preparation became common practices, easing the breakdown of food. As time passed, around 12,000 years ago, some humans transitioned to farming and domestication, leading to increased food processing and refinement.

Over several millennia, humans developed more sophisticated milling technologies, removing the tougher parts of grains, such as the germ and bran from rice and wheat. The industrial revolution subsequently accelerated these processes dramatically. As a result, many human mouths were relieved of their arduous grinding, crushing, and pulverizing duties in a relatively short time. Intriguingly, around this period, dental crookedness seems to have grown more prevalent. The study of fossils spanning millions of years reveals a gradual decrease in tooth and jaw size among humans and our ancestors. For most of human history, dietary shifts, such as the introduction of meat and the practice of cooking, were gradual, and tooth and jaw size evolved in tandem.

However, the relationship changed with the more recent agricultural and culinary revolutions. The theory suggests that over a short period, some human populations experienced a decrease in jawbone size, while teeth remained relatively unchanged in size, leading to competition for limited space. Consequently, when teeth grew in, they often displaced others and assumed eccentric positions. The arrival of wisdom teeth, usually the last to emerge, further complicated matters, as they often lacked sufficient space to erupt properly, leading to impacted wisdom teeth that caused discomfort and infections if not extracted surgically.

Larger jaws appear to be linked to greater chewing demands. Many scientists propose that as diets became less chewy due to advancements in food processing, jaw sizes diminished, resulting in dental crowding and crookedness, as well as impacted wisdom teeth. This hypothesis finds support in some preliminary experimental data. Studies on squirrel monkeys and hyraxes raised on soft or tough food revealed noticeable differences in dental crowding and arch widths, indicating that environmental and lifestyle factors play a significant role, though genetic factors may also have some influence.

Presently, an estimated 30 to 60% of people experience some degree of tooth crowding, though this trend varies across global populations. Certain individuals never develop wisdom teeth, and some experience straight teeth without any issues with their wisdom teeth. Such variations seem to correlate with diets that are less processed.

So, how can we tackle tooth crowding early through lifestyle changes and orthodontics? It's undoubtedly a topic worth pondering and exploring further.