This article was written by Ariadne Letterprofessor of dentistry and Seth M. Weinbergprofessor of oral and craniofacial science and human genetics, for the conversation. Faculty members and researchers who want to learn more about publishing in The Conversation can read about the process here.
Why do people have wisdom teeth? — Jack J., 17, Dedham, Massachusetts
Wisdom teeth are the third set of molars located in the back of the mouth. They look exactly like the first and second molars, but sometimes they can be a little smaller.
They are commonly called wisdom teeth because they are the last of the 32 permanent teeth to appear, emerging between the ages of 17 and 25, when you are older and wiser.
You may know that not everyone grows in all four wisdom teeth. You may also know that many people pull them. So it’s fair to ask – why do people have them?
We study teeth, and we can tell you the answer has a lot to do with the distant past — and a little with the present.
Stronger jaws
Just as you have many characteristics in common with people you are related to, humans share characteristics with their extended family – the primates. Monkeys, gorillas and chimpanzees everyone has wisdom teeth.
A few million years ago, early human ancestors had larger jaws and teeth than humans do today. For example, a species called Australopithecus afarensis, nicknamed Lucy’s species, lived about 3 to 4 million years ago.
The jaw and teeth of one A. afarensis individually they were quite a bit bigger and thicker than yours. They had three large molar teeth with thick enamel. The fossilized skulls of some of these very early humans also show evidence of powerful masticatory muscles.
Dietary changes
Scientists believe that they needed stronger jaws and teeth because the foods that early human ancestors ate, such as raw meat and plants, were much harder to chew than food today. Researchers look at things like marks and microscopic wear patterns on fossilized teeth to figure out what extinct ancestors might have eaten.
Today’s food is much softer than in the past due to many factors, including farming, cooking and food storage. Softer, easier-to-chew food means the teeth have less work to do. As a result, modern human jaws have evolved to be smaller and faces flatter than our extinct ancestors because our meals don’t require the same large, sharp teeth that theirs did.
Given these changes, which occurred very slowly over millions of years, the third molars – the wisdom teeth – may not be as important now as they once were.
Wisdom teeth are missing
About 25% of people today are missing at least one wisdom tooth completely, i.e. never formed at all. While people occasionally do not grow back teeth, it is much more common for wisdom teeth.
Scientists aren’t sure why this happens, but it may have something to do with the genes you inherit from your parents. Some scientists have argued that the lack of wisdom teeth is an advantage for modern humans with a smaller jaw. It’s definitely easier to fit fewer teeth into a smaller jaw.
Sometimes, due to lack of space, wisdom teeth can get stuck inside the jawbone and never fully emerge – or only partially emerge.
But wisdom teeth usually do not need to be removed if they are fully repositioned in the mouth, properly positioned and healthy.
Dentists can examine your mouth to see if your wisdom teeth are present, or look at x-rays of your jaw if those last molars haven’t yet erupted and you suspect they may be impacted.
Dentists can also advise you if any treatment – or removal – is recommended for your wisdom teeth. In the meantime, brushing at least twice a day and flossing daily will help keep all your teeth healthy.
Weird guys is a series for children of all ages. If you have a question you’d like an expert to answer, send it curiouskidsus [at] theconversation.com.
Photo by Nizil Shah/Wikimedia Commons
