Why Do We Have Wisdom Teeth? A Look at Evolution.

Dr. Lieblick: Welcome back to Oral Surgery Insights. I’m Dr. Russ Lieblick, and as always, I'm joined by my friend and partner, Dr. Brandon Rehrer. Brandon, a question we undoubtedly hear from countless patients, often with a sense of bewilderment, especially after they've undergone wisdom tooth removal, is simply: why do we even have these teeth?

Dr. Rehrer: It's a very common and perfectly valid question, Russ. These third molars, showing up much later than our other teeth, frequently cause problems for people today. Understanding why they're here means we need to look back at our human evolutionary journey, exploring the diets and physical features of our distant ancestors. It really is quite an interesting story.

Dr. Lieblick: It truly is. To get a sense of the original role of wisdom teeth, we have to picture the environment and diet of our early ancestors. What they ate daily was very coarse, tough, and abrasive – things like raw plants, roots, nuts, seeds, and uncooked meats. This kind of diet really demanded a lot of chewing power and a large molar surface area for grinding.

Dr. Rehrer: Precisely. The jaws of our early ancestors were bigger and stronger than modern human jaws. This gave them more space for three sets of molars on each side, top and bottom, to handle that demanding diet. The third molars, or wisdom teeth, were the last ones to come in, usually in late adolescence or early adulthood. They provided a fresh set of grinding surfaces right when the other molars might have been showing significant wear from years of chewing abrasive foods.

Dr. Lieblick: So, way back then, wisdom teeth weren't a problem at all: they were a key part of the chewing system, adding valuable grinding capacity throughout a person's life. The wear and tear on teeth from such a diet was pretty intense, so having these "reserve" molars show up later was a clear advantage.

Dr. Rehrer: The shift away from needing them so much started with big changes in human behavior and diet over thousands of years. A major one was learning to use fire and starting to cook food. This basic innovation really changed things for our ancestors' nutrition and, as a result, their physical makeup.

Dr. Lieblick: Cooking foods, whether plants or animals, makes them a lot softer and easier to chew and digest. Plant cell walls get broken down, and proteins in meat change their structure – essentially pre-processing the food. This cut down on the sheer physical work needed for chewing. Less force, less grinding.

Dr. Rehrer: At the same time, when early humans developed tools for cutting, pounding, and grinding food, that also lessened the mechanical strain on their teeth and jaws. As our ancestors got better at processing food before eating it, the biological need for extra-large jaws and a lot of molar grinding surface started to fade.

Dr. Lieblick: This change in diet is thought to be a major evolutionary force that shaped our facial structure. As softer, more processed foods became typical, there was a gradual trend toward smaller jaw sizes – a more refined-looking facial skeleton – over many generations. The advantage of having massive jaw architecture wasn't as strong.

Dr. Rehrer: This reduction in jaw size, though, didn't necessarily happen at the same speed as changes in tooth size or the genetic instructions for how many teeth we have. How our teeth develop is a complex genetic process, and it seems the genes for developing third molars stuck around even as our jaws got smaller.

Dr. Lieblick: And that leads to the problem we often see today. Our relatively smaller jaws frequently don't have enough space for these third molars to come in properly and function well. This lack of space is the main reason wisdom teeth can become an issue.

Dr. Rehrer: When there isn't enough room for wisdom teeth to erupt fully and line up correctly with the other teeth, they can get stuck, or impacted. Impaction means the tooth basically can't make its way completely through the gum line or into its proper spot in the dental arch.

Dr. Lieblick: Impacted wisdom teeth can show up in different ways – they might be angled forward, backward, sideways, or stay completely covered by bone or partly by gum tissue. Any of these situations can lead to a variety of clinical problems.

Dr. Rehrer: For instance, wisdom teeth that have only partly erupted are notoriously tough to keep clean. This can allow food bits and bacteria to collect around the tooth and under the gum flap covering it, a condition we call pericoronitis. This commonly causes pain, swelling, local infection, and sometimes even makes it hard to open the jaw.

Dr. Lieblick: Impacted wisdom teeth can also push on the adjacent second molars. This could potentially damage those important teeth by causing their roots to wear away or by leading to decay if food gets trapped between them. Also, though much less common, cysts or tumors can sometimes form from the tissues around an impacted wisdom tooth, which could lead to bone damage if not found and treated.

Dr. Rehrer: Just having these impacted or poorly positioned third molars, even if they aren't causing pain right away, can create ongoing inflammation, affect the health of nearby teeth, or put someone at risk for sudden problems down the line. This evolutionary mismatch between tooth size and jaw size is at the heart of most modern wisdom tooth troubles.

Dr. Lieblick: The story gets even more interesting when we look at how genetics influences wisdom tooth development. Not everyone develops all four wisdom teeth; some people are actually born without one or more, a condition called agenesis.

Dr. Rehrer: That's right. The genetic plan for tooth development is complicated, with many genes involved. Changes or variations in these genes can lead to differences in the number, size, and shape of teeth, including third molars. Studies in different groups of people show varying numbers of individuals missing third molars, from a small fraction to over a third in some populations.

Dr. Lieblick: This genetic variation explains why some people never have wisdom teeth form at all, or maybe only one or two, and so they completely sidestep potential impaction problems. For these individuals, it’s almost as if evolution has already "fixed" the issue by not creating these teeth that are often no longer needed.

Dr. Rehrer: Genetics also plays a part in when wisdom teeth develop and erupt, and their size and shape relative to the available jaw space. A family history of impacted or missing wisdom teeth can sometimes give us clues, though it’s not a perfect way to predict what will happen due to the complex mix of multiple genes and environmental factors.

Dr. Lieblick: Looking at it from a broader anthropological view also shows some interesting differences. In some indigenous groups today who still eat foods much like their ancestors did – coarse, fibrous foods needing a lot of chewing – we tend to see larger jaw development and fewer wisdom tooth impactions compared to people in industrialized societies who mainly eat softer, processed diets.

Dr. Rehrer: This suggests that while our genes provide the basic instructions, other factors like how much we use our jaw muscles during development might also affect jaw growth and whether third molars fit or become impacted. It's a fascinating connection between our deep evolutionary past and our more recent dietary and cultural habits.

Dr. Lieblick: So, if we bring this whole evolutionary journey into how we practice dentistry today, the reason wisdom teeth often need to be managed or removed isn't because they are inherently "bad" teeth. It's more that our modern anatomy and environment often don't give them the room to function like they once did for our ancestors.

Dr. Rehrer: Perfectly put. The potential for them to cause pain, infection, damage to nearby teeth, or other issues when impacted or poorly positioned means that checking them and, when appropriate, removing them in a timely way becomes an important part of preventative and therapeutic oral healthcare.

Dr. Lieblick: Understanding this evolutionary background can be quite useful for patients. It helps explain why these teeth, which were once so helpful, can now be a source of problems, not through any fault of the patient, but because of this long biological story of changes in diet and facial structure. It helps frame the discussion about why we might recommend monitoring or removal.

Dr. Rehrer: And it underscores why regular dental checkups, which include X-ray assessments during adolescence and early adulthood, are important for keeping an eye on wisdom tooth development and eruption. Spotting potential problems early allows for timely intervention, often meaning simpler procedures and smoother recoveries if removal is necessary.

Dr. Lieblick: In summary, Brandon, the story of our wisdom teeth is truly a compelling part of human evolution. They are a fascinating leftover from a time when our ancestors' diets and jaw structures were very different, serving a key function that has largely become unnecessary for many people today.

Dr. Rehrer: Indeed, Russ. The shifts in diet and the resulting changes in our facial anatomy explain why these third molars, once so beneficial, often present challenges now. Understanding this long biological history offers a valuable perspective for both us as clinicians and for our patients.

Dr. Lieblick: It’s a reminder of how interconnected our bodies are with our evolutionary past. We sincerely thank everyone for joining us on Oral Surgery Insights for this exploration. We trust this discussion has been enlightening.

Dr. Rehrer: We appreciate you spending your time with us and hope this conversation has provided some interesting insights into a very common dental topic.

Dr. Lieblick: We wish you continued health and well-being. Thanks for listening.