"Ah ~ ~ hiss ~ hiss, ah ~ (╥ ╯ ^ ╰ ╥) · · "
When everyone comes out of the examination room with their wisdom teeth pulled out and covered their faces, do they have such a question in their heads:
If wisdom teeth need to be removed, then why do we still have wisdom teeth?
Before answering the question of why we should have wisdom teeth removed, let's first understand what wisdom teeth are.
part.1
It's not about making room for a longer brain
Wisdom teeth, also known as "third molars", usually do not erupt after the age of 17, and are the last teeth to grow in our lives. At this time, the master's mind has matured, so people associate it with wisdom, and there is the "good name" of wisdom teeth.
The position of the third molar, the "wisdom teeth"
But for some, wisdom teeth seem to be a biological misfortune, and these "extra" molars don't seem to be well suited to his/her mouth. Because wisdom teeth erupt late, there is no place for them in the mouth when they erupt, so they are often in a state of obstruction, which will cause many oral diseases, so that a large number of wisdom teeth are removed from the mouth by doctors every year.
What you may not know, though, is that our wisdom teeth have shrunk by a fraction compared to our ancestors and close relatives. In modern humans, wisdom teeth are usually very small or even undeveloped; in many ancient humans, wisdom teeth are relatively large, and their chewing surface is even twice that of modern humans.
Specifically, in the course of 7 million years of evolution, due to the increase in brain volume, the human jawbone has become shorter and shorter, and this change has gradually made the wisdom teeth that still have a place gradually become nowhere to be placed. But the jaw is short and short, the long teeth are still long, in order to make the jawbone able to put down all teeth, human teeth become smaller and smaller, of which the most obvious trend is the third molar (m3), which is located at the back of the mouth (m3), that is, wisdom teeth.
Researchers have measured and analyzed many fossils of ancient humans and found that several species of homo (such as Homo) (such as Homo) have chewed areas with wisdom teeth that are almost smaller than australopithecus and ardipithecus. Even in the genus Homo erectus, which appeared 2 million years ago, had 1.5 times the area of wisdom teeth chewed by modern humans.
However, you may also find that although the chewing area of wisdom teeth is decreasing, in the fossil dentition mentioned above, wisdom teeth look quite normal, far from being like now, showing an annoying obstructed state.
So the question is, if our wisdom teeth are like our ancestors, looking obedient, then not only do not have to be removed, but also provide additional chewing function, is this not in vain to earn four tooth implant money (crooked, Nobel, when will the economics prize be awarded to me)?
In fact, among modern people, some people's wisdom teeth behave very normally, and the highest edge of the crown of wisdom teeth is flush with the occlusal plane, if it is not pathological, it does not need to be removed.
Therefore, when we ask "why do we want to extract wisdom teeth", we are actually asking such a question: Why do some people's wisdom teeth show a pathological obstructed state?
The answer to this question is not just because our jaws are getting shorter.
part.2
Humans eat "soft rice", and wisdom teeth come to carry the pot
As we all know, the evolution of the jaw is actually a very long process, when comparing the size of the jaws of contemporary people and centuries ago, researchers did not find significant differences, so what is the problem?
Let's open the pattern and simply analyze a wave: if the jawbone does not change significantly, then in the case of limited space, is the difference in the use of space by the teeth?
The answer may be yes.
When studying individual teeth, scientists found that 500 years ago, people had a much higher rate of wear and tear on their teeth, and that rough diets increased the wear and tear between teeth, which in turn reduced the overall length and width of teeth, and tooth replacement was a gradual process, which allowed people at that time to stuff 32 teeth in the same limited space. Compared with people 500 years ago, the soft diet makes the gap between our teeth increase (no wonder what to eat), and in the end, there is very little room for wisdom teeth, which is one of the reasons why the proportion of contemporary human crowns covered by other tissues is much higher (75%).
You may also have noticed that the essence of the problem is that the food we eat now is getting softer and softer.
Over the course of human evolution, changes in our teeth seem to coincide with changes in diet and food preparation techniques:
In the Age of Homo erectus, people had mastered the use of stone tools to knock and cook food, which made chewing easier, and huge teeth grinding began to become less important for Homo erectus;
About 12,000 years ago, humans began experimenting with farming and domesticating wild animals. This lifestyle change allows humans to produce wheat flour, milk, and then make softer foods, and people's teeth are getting smaller and smaller;
Nowadays, industrial production has made our food more delicate and soft, and with it, more and more people have the pathological obstruction of wisdom teeth and can only seek help from dentists.
Some students may ask, is it not space-saving to make teeth smaller, so that even if the jawbone becomes shorter, wisdom teeth can have a place to stay
There was nothing wrong with this before the advent of the industrial era, after all, the "soft" food of that time, well, may be placed in the present, is not so chewy. The advent of the industrial era completely upset the delicate balance between tooth size and jaw length. From an evolutionary perspective, centuries are short-lived—there's barely enough time for our teeth and jaws to adapt to the changes that come with soft, processed foods.
In fact, soft food not only makes the gap between modern people's teeth larger, the lack of chewing exercise will further affect the development of people's mandibles, and under this circumstance, the wisdom teeth that finally sprout naturally have no place to stay, becoming a troublesome problem.
When we have cleared up our thinking, it is not difficult to find that the pathological wisdom tooth impact that occurs frequently in modern people may be a developmental problem, rather than an evolutionary problem, which allows us to solve the problem of wisdom teeth through ways other than tooth extraction.
part.3
Get away from wisdom teeth and try a different way of eating
Scientists have long noticed that many problems associated with dentition in modern people, such as wisdom tooth impact, crowded teeth, and misalignment, may not be rooted in genetic differences, but in lifestyle differences. A past study has shown that hunter-gatherers have relatively long and narrow jaws, while people who depend on farming have relatively short and wide mandibles, so that shorter mandibles are prone to more dental problems.
Obviously, in just a few generations, the power of evolution is not enough to make our jaws shrink significantly. Similarly, there is no evidence that selection pressure causes people with longer jaws to produce more offspring, making this trait permanent.
On the contrary, different lifestyles can cause significant physiological changes in the population in a short period of time. For example, since World War II, Japanese men have shifted from eating a lot of rice to eating more dairy and protein in childhood, which has increased the average height of Japanese men as adults by about 5 inches.
Such a significant change is also manifested in the form of the jaw, taking the three generations of grandchildren in India as an example, the grandfather was born in the countryside of India, came to the United Kingdom with children when he was young, and the grandson was born in industrialized society, but it is the time of the three generations of grandchildren, we can find that the grandson is already obviously "heavenly" compared to the grandfather.
Therefore, many scientists recommend adding some hard and crisp foods to your child's plate, some extra fruits, vegetables and nuts, which may save your child from the trouble of wisdom teeth extraction when he grows up.
But the older kids in front of the screen don't have to be discouraged, and in a new study published in Science Advances, scientists found that the human mandibular dental arch does not continue to elongate until the age of 22.
So...
Good life, starting with a chin exercise?
Editor/Jing Wang
【Source: China Science Expo】
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