10 Smart Facts About Wisdom Teeth

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Like puberty and your first heartbreak, the painful process of getting your wisdom teeth removed is one of those cumbersome coming-of-age rituals that many people are forced to endure. But why do we have wisdom teeth when they seem to only cause problems? Read on to find out more about the humble third molar—the last tooth many of us get as adults.

1. THEY HAVEN’T SERVED ANY PURPOSE FOR HUNDREDS OF THOUSANDS OF YEARS.

Imagine, for a moment, that you’re a prehistoric man or woman. You subsist largely on raw meat, roots, and leaves. You’d need some pretty powerful chompers to cut up your food, right? That was where your third molars—also known as wisdom teeth—came in. Today, our palates are a little more refined, and we prefer softer foods (think avocado toast and smoothies). Plus, modern cooking tools have put our wisdom teeth out of business.

They’re not just pointless, though—they’re also problematic. Wisdom teeth are a “scar of human evolution,” according to Princeton University researcher Alan Mann. About 800,000 to 200,000 years ago, early humans’ brains started growing at a rapid pace—so much so that they ballooned to three times their original size. When that happened, it changed the shape of the braincase (the back part of the skull) and its position relative to the dental arcade (rows of teeth). The dental arcade shortened, and suddenly there was no longer enough room for third molars. And since the genes that determine the makeup of our teeth evolve separately from those that control brain development, humans were stuck dealing with the consequences of a crowded mouth, according to Live Science.

2. NATURE MAY EVENTUALLY SORT IT OUT, THOUGH.

On the bright side, scientists say evolution may eventually take care of the problem, meaning that people in the future would not develop wisdom teeth. It’s anyone’s guess as to when this will occur, though. “On the evolutionary scale, if I had to predict down the road—centuries probably—wisdom teeth are going to be one of the things that humans probably won’t have anymore,” Dr. William McCormick, assistant clinical professor at West Virginia University’s School of Dentistry, tells Mental Floss.

3. THE NUMBER OF WISDOM TEETH VARIES FROM PERSON TO PERSON ...

It’s possible that you have one, two, three, four, or none at all. Another possibility, although it’s rare, is to have more than four wisdom teeth, which are called supernumerary teeth. “In my career, I have seen two cases where patients have had fourth molars—or two sets of wisdom teeth,” McCormick says. (Comparatively, humans’ ancestors had quite the mouthful, with 12 wisdom teeth in total.)

According to McCormick, genetic factors like jaw size might determine the number of wisdom teeth that a person has. Your lineage may also have something to do with it. Practically no Aboriginal Tasmanians have third molars, but almost 100 percent of indigenous Mexicans have at least one wisdom tooth. African Americans and Asian Americans are also more likely than people of European descent to have fewer than four wisdom teeth. This variation can be attributed to a random genetic mutation that arose thousands of years ago, thereby preventing the formation of wisdom teeth. This mutation is more prevalent in certain populations.

4. ... AS DOES THE NUMBER OF ROOTS THAT EACH TOOTH HAS.

The roots are the part of the tooth that form first, and then push the bud (the part that's visible in your mouth) through your gums. While wisdom teeth typically have two or three roots, they can have more. McCormick says he personally removed his wife’s wisdom teeth in the ‘70s and was surprised to see that one of them had five roots. “It looked like a spider. It was not a pleasant extraction,” he says.

For that reason, if wisdom teeth need to be removed, it’s easier to do so before the roots start to take hold. “When the roots are totally formed, they’re anchored like a tree that’s been in your backyard for 100 years,” says Dr. Ron Good, an orthodontist in southwestern Pennsylvania who runs a family practice with his brother, Dr. Bob Good. On the other hand, surgeons want some roots to grab hold of, because removing a tiny tooth bud is “like extracting a marble,” Dr. Ron tells Mental Floss.

5. YOUR WISDOM TEETH CAN ERUPT AT ANY TIME.

According to Guinness World Records, the oldest person to ever grow a wisdom tooth was 94 years old. McCormick says there's a wide variation in ages when eruption occurs; he once had a 65-year-old patient with dentures whose wisdom tooth had started to erupt (poke through the gums). “They’re crazy little beasts. You never know what you’re going to see.”

Apparently, wisdom teeth have been acting erratically for thousands of years. Aristotle documented this phenomenon in his book The History of Animals: “Cases have been known in women upwards of 80 years old where at the very close of life the wisdom-teeth have come up, causing great pain in their coming; and cases have been known of the like phenomenon in men too.”

In most cases, though, wisdom teeth erupt when you’re in your late teens or early twenties.

6. THE FIRST IMPACTED TOOTH WAS RECORDED ABOUT 15,000 YEARS AGO.

When wisdom teeth don’t have enough room to grow normally, they get stuck in the jaw and fail to erupt. These are called impacted teeth. The oldest known case of an impacted tooth was found in the skeleton of a 25- to 35-year-old woman who died some 15,000 years ago. This case cast doubt on the theory that impacted teeth are a modern ailment, caused by recent changes in our dietary habits.

7. SOME PHYSICIANS SAY THAT IMPACTED WISDOM TEETH SHOULD BE SURGICALLY REMOVED ...

Many people get their wisdom teeth removed, even if there isn’t any pain or discernible problem aside from impacting. Known as prophylactic surgery, this preventative practice is common in the U.S., but in recent years there has been some debate as to whether it’s necessary. One popular theory holds that most people either have problems with their wisdom teeth or will at some point in the future. “It’s hard to get a percentage, but probably 75 to 80 percent of people do not meet the criteria of being able to successfully maintain their wisdom teeth,” Dr. Louis K. Rafetto, who headed a task force on wisdom teeth, told The New York Times in 2011.

About 3.5 million extraction surgeries are performed each year, and according to another estimate, that adds up to be 10 million individual wisdom teeth pulled annually. Dr. Ron and Dr. Bob, of Good Orthodontics, are both of the opinion that wisdom teeth are ticking time bombs. “In our mind, we feel that wisdom teeth, in general, are of no value and are only potential problems,” Dr. Bob says. He added that third molars can interfere with your bite and cause your teeth to wear down, and in some cases, can also cause cysts, tumors, nerve damage, periodontal disease (affecting the gums and other areas around the teeth) and TMJ disorders (affecting the jaw joint). Plus, if your teeth are too crowded and you aren’t able to brush and floss them normally, it can lead to additional issues, such as gum disease and cavities.

8. ... WHILE OTHERS SAY YOU SHOULD AVOID IT.

Dental practitioners in the UK put an end to routine wisdom tooth extractions in 1998, citing a study at the University of York that reportedly found no scientific evidence to support the practice, according to the The Miami Herald.

Opposition is building in the U.S., too. Retired dentist Dr. Jay Friedman told How Stuff Works that only about 12 percent of wisdom teeth eventually cause problems. He compared that rate to the 7 to 14 percent of people who experience appendicitis, yet appendixes aren’t removed until they become a medical issue. If this seems to contradict Raffeto's statistics, it’s because there isn’t a whole lot of concrete data on the subject, and much of it is conflicting—so it really comes down to the individual physician’s and patient's preferences. “Ask three dentists the same question, and you’re going to get four different answers,” McCormick says with a laugh.

Like Friedman, McCormick doesn't support wisdom tooth removal unless there’s an infection, abscess, or other problem. “You have to weigh the surgical risk with what you’re going to try to accomplish,” he says. Like any surgery, wisdom tooth extraction poses a risk, although more serious complications, like fractured jaws and death, are extremely rare. McCormick says some possible side effects include nerve damage, infection, and dry socket (an infection of the tooth socket).

Despite the differing opinions in the dental community, McCormick, Dr. Ron, and Dr. Bob agreed that there’s no prescriptive rule for wisdom tooth removal, and that each patient should be evaluated on a case-by-case basis.

9. THEY’RE CALLED LOVE TEETH IN KOREAN.

In English, the name wisdom tooth conveys the idea that third molars come in later than other teeth, at a time when you’re older and (hopefully) wiser. Other languages don’t follow the same convention. In Korean, for example, the poetic name for third molars translates to “love teeth,” because it's around this time (late teens and early 20s) that one typically experiences their first love. The Japanese language also has a creative word for it: oyashirazu, or “unknown to parents,” since most people have already moved away from home by the time their wisdom teeth come in.

10. THEY’RE USED IN STEM CELL RESEARCH.

It turns out wisdom teeth aren't all bad. Although some of the research is still in the experimental phase, scientists are studying dental stem cells—which were discovered in 2003—to see if they can potentially be used to repair and regenerate tissue.

One study on mice, at the University of Pittsburgh’s School of Medicine, found that stem cells taken from wisdom teeth could someday be used to repair corneas that have been scarred by infection or injury. Any clinical applications for humans would require more research, though.

"There are studies with dental pulp cells being used to treat neurological disorders and problems in the eye and other things,” Dr. Pamela Robey, of the National Institute of Dental and Craniofacial Research, told CNN. “The problem is, these studies have really not been that rigorous ... the science needs a lot more work.”

25 Amazing Facts About the Human Body

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The human body is an amazing piece of machinery—with a few weird quirks.

  1. It’s possible to brush your teeth too aggressively. Doing so can wear down enamel and make teeth sensitive to hot and cold foods.

  2. Goose bumps evolved to make our ancestors’ hair stand up, making them appear more threatening to predators.

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  1. Wisdom teeth serve no purpose. They’re left over from hundreds of thousands of years ago. As early humans’ brains grew bigger, it reduced space in the mouth, crowding out this third set of molars.

  2. Scientists aren't exactly sure why we yawn, but it may help regulate body temperature.

  3. Your fingernails don’t actually grow after you’re dead.

  4. If they were laid end to end, all of the blood vessels in the human body would encircle the Earth four times.

  5. Humans are the only animals with chins.

    An older woman's chin
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    1. As you breathe, most of the air is going in and out of one nostril. Every few hours, the workload shifts to the other nostril.

    2. Blood makes up about 8 percent of your total body weight.

    3. The human nose can detect about 1 trillion smells.

    4. You have two kidneys, but only one is necessary to live.

    5. Belly buttons grow special hairs to catch lint.

      A woman putting her hands in a heart shape around her belly button
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      1. The satisfying sound of cracking your knuckles comes from gas bubbles bursting in your joints.

      2. Skin is the body’s largest organ and can comprise 15 percent of a person’s total weight.

      3. Thumbs have their own pulse.

      4. Your tongue is made up of eight interwoven muscles, similar in structure to an elephant’s trunk or an octopus’s tentacle.

      5. On a genetic level, all human beings are more than 99 percent identical.

        Identical twin baby boys in striped shirts
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        1. The foot is one of the most ticklish parts of the body.

        2. Extraocular muscles in the eye are the body’s fastest muscles. They allow both of your eyes to flick in the same direction in a single 50-millisecond movement.

        3. A surgical procedure called a selective amygdalohippocampectomy removes half of the brain’s amygdala—and with it, the patient’s sense of fear.

        4. The pineal gland, which secretes the hormone melatonin, got its name from its shape, which resembles a pine nut.

        5. Hair grows fast—about 6 inches per year. The only thing in the body that grows faster is bone marrow.

          An African-American woman drying her hair with a towel and laughing
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          1. No one really knows what fingerprints are for, but they might help wick water away from our hands, prevent blisters, or improve touch.

          2. The heart beats more than 3 billion times in the average human lifespan.

          3. Blushing is caused by a rush of adrenaline.

12 Intriguing Facts About the Intestines

When we talk about the belly, gut, or bowels, what we're really talking about are the intestines—long, hollow, coiled tubes that comprise a major part of the digestive tract, running from the stomach to the anus. The intestines begin with the small intestine, divided into three parts whimsically named the duodenum, jejunum, and ileum, which absorb most of the nutrients from what we eat and drink. Food then moves into the large intestine, or colon, which absorbs water from the digested food and expels it into the rectum. That's when sensitive nerves in your rectum create the sensation of needing to poop.

These organs can be the source of intestinal pain, such as in irritable bowel syndrome, but they can also support microbes that are beneficial to your overall health. Here are some more facts about your intestines.

1. The intestines were named by medieval anatomists.

Medieval anatomists had a pretty good understanding of the physiology of the gut, and are the ones who gave the intestinal sections their names, which are still used today in modern anatomy. When they weren't moralizing about the organs, they got metaphorical about them. In 1535, the Spanish doctor Andrés Laguna noted that because the intestines "carry the chyle and all the excrement through the entire region of the stomach as if through the Ocean Sea," they could be likened to "those tall ships which as soon as they have crossed the ocean come to Rouen with their cargoes on their way to Paris but transfer their cargoes at Rouen into small boats for the last stage of the journey up the Seine."

2. Leonardo da Vinci believed the intestines helped you breathe.

Leonardo mistakenly believed the digestive system aided respiratory function. In 1490, he wrote in his unpublished notebooks, "The compressed intestines with the condensed air which is generated in them, thrust the diaphragm upwards; the diaphragm compresses the lungs and expresses the air." While that isn't anatomically accurate, it is true that the opening of the lungs is helped by the relaxation of stomach muscles, which does draw down the diaphragm.

3. Your intestines could cover two tennis courts ...

Your intestines take up a whole lot of square footage inside you. "The surface area of the intestines, if laid out flat, would cover two tennis courts," Colby Zaph, a professor of immunology in the department of biochemistry and molecular biology at Melbourne's Monash University, tells Mental Floss. The small intestine alone is about 20 feet long, and the large intestine about 5 feet long.

4. ... and they're pretty athletic.

The process of moving food through your intestines requires a wave-like pattern of muscular action, known as peristalsis, which you can see in action during surgery in this YouTube video.

5. Your intestines can fold like a telescope—but that's not something you want to happen.

Intussusception is the name of a condition where a part of your intestine folds in on itself, usually between the lower part of the small intestine and the beginning of the large intestine. It often presents as severe intestinal pain and requires immediate medical attention. It's very rare, and in children may be related to a viral infection. In adults, it's more commonly a symptom of an abnormal growth or polyp.

6. Intestines are very discriminating.

"The intestines have to discriminate between good things—food, water, vitamins, good bacteria—and bad things, such as infectious organisms like viruses, parasites and bad bacteria," Zaph says. Researchers don't entirely know how the intestines do this. Zaph says that while your intestines are designed to keep dangerous bacteria contained, infectious microbes can sometimes penetrate your immune system through your intestines.

7. The small intestine is covered in "fingers" ...

The lining of the small intestine is blanketed in tiny finger-like protrusions known as villi. These villi are then covered in even tinier protrusions called microvilli, which help capture food particles to absorb nutrients, and move food on to the large intestine.

8. ... And you can't live without it.

Your small intestine "is the sole point of food and water absorption," Zaph says. Without it, "you'd have to be fed through the blood."

9. The intestines house your microbiome. 

The microbiome is made up of all kinds of microorganisms, including bacteria, viruses, fungi, and protozoans, "and probably used to include worm parasites too," says Zaph. So in a way, he adds, "we are constantly infected with something, but it [can be] helpful, not harmful."

10. Intestines are sensitive to change.

Zaph says that many factors change the composition of the microbiome, including antibiotics, foods we eat, stress, and infections. But in general, most people's microbiomes return to a stable state after these events. "The microbiome composition is different between people and affected by diseases. But we still don't know whether the different microbiomes cause disease, or are a result in the development of disease," he says.

11. Transferring bacteria from one gut to another can transfer disease—or maybe cure it.

"Studies in mice show that transplanting microbes from obese mice can transfer obesity to thin mice," Zaph says. But transplanting microbes from healthy people into sick people can be a powerful treatment for some intestinal infections, like that of the bacteria Clostridium difficile, he adds. Research is pouring out on how the microbiome affects various diseases, including multiple sclerosis, Parkinson's, and even autism.

12. The microbes in your intestines might influence how you respond to medical treatments.

Some people don't respond to cancer drugs as effectively as others, Zaph says. "One reason is that different microbiomes can metabolize the drugs differently." This has huge ramifications for chemotherapy and new cancer treatments called checkpoint inhibitors. As scientists learn more about how different bacteria metabolize drugs, they could possibly improve how effective existing cancer treatments are.

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