7 Surprising Facts About the Chin

iStock
iStock

The human body is an amazing thing. For each one of us, it’s the most intimate object we know. And yet most of us don’t know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

The humble chin, that bony protrusion at the bottom of your face, is a mysterious little body part that is a surprising source of controversy among researchers. Though popular culture derives great meaning out of how "strong" or "weak" chins are, very little science backs that up. Here, however, are seven actually scientific facts, which Mental Floss learned from experts, about the chin.

1. RESEARCHERS DISAGREE ABOUT THE PURPOSE OF A CHIN.

The most interesting thing about the chin, according to Faisal Tawwab, a family practice doctor with Multicare Physicians in Orlando, Florida, is that there is no precise answer as to why we even have one. "Prevailing theories include assistance with speech, to protect the jaw from chewing, as a way to measure attractiveness when seeking a partner, or a combination of all three," he tells Mental Floss. "Research to find the true purpose of the chin is ongoing. There are critiques around all of the current prevailing theories."

2. IT MIGHT HELP THE JAW STRESS LESS.

The chin may have evolved to protect the jaw from the unique stresses of shaping our mouths to form language, according to a 2007 study in the journal Medical Hypotheses. Your chin may help bear some of the muscle load of chewing and speaking (a valid reason to want a strong one).

3. THE CHIN IS CRITICAL TO CHEWING.

"The most important function of the chin is mastication [chewing] and lip continence," Francesco Gargano, a board certified plastic surgeon with The Plastic Surgery Center in New Jersey, tells Mental Floss. "Several muscles insert into the chin and are part of the occlusal plane," the space between your teeth when the mouth is closed. Research supports this theory, suggesting that the chin "helps buttress the jaw against certain mechanical stresses," including chewing, which produces a great deal of force.

4. CHINS MAY HAVE HELPED OUR ANCESTORS CHOOSE A MATE.

A more recent theory is that our chins helped us choose mates. "Males tend to have longer chins with a square appearance and flat base. Females tend to have narrower and rounder chins," says Gargano. A 2010 study in the American Journal of Physical Anthropology argues that there would be no difference in chin shape if it weren't related to sexual attraction because there's no functional difference; males and females ostensibly eat and talk the same way. Not everyone agrees. (See #7.)  

5. WE'RE THE ONLY ANIMALS WITH CHINS. 

While humans may share some things in common with animals, chins are not one of them. "Elephants are the only other creature with a body part similar to the chin," Tawwab says. But the elephant's "chin" is actually caused by a lack of lower teeth and a big lower lip. It's not a bony protrusion, which is a real chin—and a feature that's ours alone. The human chin is considered a cladistic apomorphy, Tawwab says: a feature or body part not found in the earliest forms of a clade (group of organisms sharing a common ancestor). In short, it's evidence of our species's evolution—and one of our defining physical characteristics.

6. DOES HAVING A CHIN CLEFT IMPROVE YOUR DATING PROSPECTS? 

"Historically, numerous cultures have assigned meanings to being born with a cleft chin, usually pertaining to luckiness in love," Tawwab says. The reality is much more mundane. "The current theory suggests that a cleft chin is actually caused by an incomplete fusion of the jaw bones before birth." There are several types of clefts, as well: vertical furrows, Y-shaped furrows, and round dimples. 

7. A CHIN MAY SIMPLY BE WHERE EVOLUTION STOPPED.

A chin may not have anything to do with withstanding pressure or attracting a mate, according to Nathan Holton, an anthropologist at the University of Iowa. His research suggests that the Homo genus (including humans, Neanderthals, and other relatives) simply evolved smaller faces—and Homo sapiens most of all. The lower jaw is the last part of the face to stop growing, which causes it to be more prominent as compared to other parts of the face. The prominent chin "is a secondary consequence of faces getting smaller," Holton writes.

25 Amazing Facts About the Human Body

iStock.com/kali9
iStock.com/kali9

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.

Woman's legs with goosebumps
iStock.com/MyetEck
  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
    iStock.com/mhelm3011
    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
      iStock.com/PeopleImages
      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
        iStock.com/BorupFoto
        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
          iStock.com/GlobalStock
          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.

SECTIONS

arrow
LIVE SMARTER