26 Fascinating Facts About the Human Body

Ridofranz/iStock via Getty Images Plus
Ridofranz/iStock via Getty Images Plus

You may not think about it very often, but there's so much to learn about the human body. For instance, did you know that people are actually covered in invisible stripes? In this article, which was adapted from an episode of The List Show, we take a look at some fascinating facts about the human body you might not know.

1. Only humans have chins.

Humans are the only animals with chins. While you may think every animal has one, that’s just what we tend to call the bottom of the head. But in reality, a chin is a very specific bone feature that extends forward from the lower jaw. Some experts propose that elephants and manatees have chins, but others argue that they’re such fundamentally distinct structures they shouldn’t be compared to humans. Experts still aren’t sure why people evolved to have chins; the reason might have to do with eating or speaking, or they may just have emerged as a side effect from some other useful feature.

2. Humans have a strange bone called the hyoid.

A peculiar bone humans have is the hyoid. This is the one bone that doesn’t form a joint with another bone. Instead, it’s connected to muscles and ligaments. The hyoid sits between the jaw and the voice box and it’s used to keep all the lower mouth muscles in place. It also helps with swallowing and talking.

3. People that have more hair and innie belly buttons are more prone to lint.

Hairy people with innie belly buttons are more prone to belly button lint, which comes from fibers that rub off of clothing over time. Your stomach hair grabs onto the fibers and pulls them into your belly button.

Starting in 2011, a group of scientists started the Belly Button Biodiversity Project to learn about what's going on inside these little caves of mystery, and as it turns out, it's quite a lot. Samples from about 60 people revealed over 2300 total species of bacteria. And of those, only eight were identified as common, appearing in over 70 percent of belly buttons.

4. While it varies person to person, fingernails grow faster than toenails.

Your fingernails grow faster than your toenails. Though it varies from person to person, typically, fingernails grow about a tenth of a millimeter each day, while toenails grow at around half that pace. There’s a correlation between nail growth speed and the length of the nearest bone. This means that your longest fingers have faster-growing nails than your shorter fingers.

5. Fingernails grow faster on your dominant hand.

Your fingernails grow faster on the hand that you write with. No one knows why.

6. As you age, your nails change.

Specifically, they grow more slowly and then nail cells, known as onychocytes, start accumulating. That’s why older people have thicker toenails. Fingernails aren’t as noticeably different because people manage them better, plus our toes endure a lot of damage throughout our lives.

7. It's a misconception that people's hair and nails continue to grow after they die.

What’s actually happening is the skin dehydrates and then recedes. So it looks like the hair and nails are getting longer, but in reality it's actually the skin that's getting shorter.

8. Breastfeeding will not cause breasts to sag.

It's a common misconception that breastfeeding causes breasts to sag. Pregnancy itself might affect breasts in that they may stretch and then recover differently. But research on breastfeeding confirms it will not cause breasts to sink. A behavior that will, though, is smoking.

9. Hands and feet contain over half the bones in an adult body.

With around 27 bones in each of your daddles—that’s an old slang word for the hands—and about 26 bones in each of your plates of meat—which is another old slang term for feet—these appendages account for over half of an adult’s bones, of which there are around 206 total. But that’s not always true. Feet mostly contain cartilage at birth, then bones form over time. They don’t fully harden until humans are in their early twenties.

10. You can fracture a rib just by sneezing.

While it's rare, it is possible to fracture a rib by sneezing. In 1885, there was an article in the Journal of the American Medical Association about a 72-year-old man who fractured his eighth rib while sneezing. Sneezer, by the way, is a 1940s Australian slang term meaning “excellent, wonderful,” which could definitely describe a good sneeze—but probably not one that would break a rib.

11. You can see stars if you rub your eyes.

If you've ever seen stars while rubbing your eyes, you’re not imagining it. The cells in our eyes are interpreting the pressure as an input, and treat that the same way they’d treat a light input.

12. Goosebumps are pretty much useless.

Goosebumps are frequently associated with adrenaline being released in the body, like when we’re feeling a particularly strong emotion, for example. They used to be important when people had way more hair on their bodies because goosebumps would elevate that hair and make a person look bigger when they were in danger. But now, they’re a pretty useless feature.

13. Spleens help the immune system.

The spleen is surprisingly not totally useless even though that was the belief up until the 1950s. It’s OK to get your spleen removed, but it does assist the immune system. While blood is in the spleen, the immune system creates the necessary antibodies to fight bacteria in that blood. A fetus’s spleen also creates red blood cells.

14. The appendix seems to help the immune system.

It's OK to get your appendix removed, but the organ also aids the immune system. In 2018, Dr. Mohamad Abouzeid, assistant professor and attending surgeon at NYU Langone Health told Mental Floss, "[The appendix] has a high concentration of the immune cells within its walls." Experts don't know exactly how the appendix affects the immune system, but it seems to play some role in keeping us healthy.

15. A fetus's face forms in the first three months after conception.

During the first three months after conception, a fetus’s face comes together, fusing in the area of the top of the lip. That means the dent under the nose, which is called the philtrum, is evidence of a person's time in the womb.

16. Babies don’t just see in black and white.

A newborn baby has pretty terrible vision. But it’s not true that they can only see in black and white. In reality, if there’s a large amount of the color red, they can identify it, but only if it appears in front of gray. Newborns have about 5 percent of the visual acuity that adults do, but it improves quickly and takes only around six months before they can see about as well as a grown-up. Though there are some eye tests that babies can school adults on, which are ones centered around subtlety. For example, up until 6 months old, a baby can tell monkeys apart, while older babies and adults can’t do that.

17. The liver is very good at regenerating itself.

In fact, with just 25 percent of the original liver tissue, it can regenerate. Liver transplants are generally only needed if someone has experienced severe damage to the organ or an injury.

18. Some people are born with three kidneys.

Some people had a kidney split while they were still in the womb, so they're actually born with three. This makes them prime candidates for donation, but the problem is people often don't know when they have three kidneys.

19. A person's large intestine can be stretched 5 feet and the small intestine can stretch 20 feet.

The intestines are pretty long: The small intestine stretches to about 20 feet and the large intestine hits 5 feet. The surface area of your intestines could take up two entire tennis courts, although some Swedish researchers have downgraded it to studio apartment size. Compare that with a blue whale, though, which has over 700 feet worth of intestines.

20. The stomach can hold up to 50 fluid ounces.

The stomach may not be tennis court size, but it can hold around 16 to 50 fluid ounces. It's interesting to note that a Trenta size at Starbucks is 31 fluid ounces, which is more than many adult stomachs can technically hold.

21. The neurotransmitter serotonin can be found in the gut.

Our gut contains 95 percent of the neurotransmitter serotonin. In fact, the gut, with its 100 million neurons, is so important to mood that it’s sometimes called the “second brain.” Medications that affect serotonin will often also cause GI issues.

22. The skin is the largest organ.

The skin is considered an organ and it's the body's largest one. An adult may have 22-square feet of skin on their body. Basically that means your skin could comfortably stretch across half the floor of the typical bathroom.

23. The skin makes up a large part of your body weight.

Fifteen percent of your total body weight, to be exact.

24. The ovaries are in communication with the brain.

It was once believed that the ovaries and uterus sort of sat dormant until they were needed, but the ovaries actually communicate with the brain in ways we’re just learning about. The hypothalamus and ovaries work together to make sure that the levels of hormones in the ovaries, like estrogen and progesterone, are where they need to be.

25. Humans are covered in stripes.

The human body is covered in stripes called Blaschko’s Lines, which are typically invisible. They’re cellular relics of our development from a single cell to a fully formed human.

26. Humans glow, but our eyes aren't able to detect it.

Humans glow, but it’s just around 1000 times weaker than our eyes can detect. Every animal that has metabolic reactions glows because in that process, photons get emitted, causing light. In 2009, a study was published in which a camera captured the bioluminescence of five men. According to that study, our upper body lights up the strongest. And the glow is on a cycle; when we’re on a normal sleep schedule, our bioluminescence is at its strongest at about 4 p.m.

13 Father's Day Gifts for Geeky Dads

Amazon/Otterbox/Toynk
Amazon/Otterbox/Toynk

When in doubt, you play the hits. Watches, flasks, and ties are all tried-and-true Father’s Day gifts—useful items bought en masse every June as the paternal holiday draws near. Here’s a list of goodies that put a geeky spin on those can’t-fail gifts. We’re talking Zelda flasks, wizard-shaped party mugs, and a timepiece inspired by BBC’s greatest sci-fi series, Doctor Who. Light the “dad” signal ‘cause it’s about to get nerdy!

1. Lord of the Rings Geeki Tikis (Set of Three); $76

'Lord of The Rings' themed tiki cups.
Toynk

If your dad’s equally crazy about outdoor shindigs and Tolkien’s Middle-earth, help him throw his own Lothlórien luau with these Tiki-style ceramic mugs shaped like icons from the Lord of the Rings saga. Gollum and Frodo’s drinkware doppelgängers each hold 14 ounces of liquid, while Gandalf the Grey’s holds 18—but a wizard never brags, right? Star Wars editions are also available.

Buy it: Toynk

2. Space Invaders Cufflinks; $9

'Space Invaders' cufflinks on Amazon
Fifty 50/Amazon

Arcade games come and arcade games go, but Space Invaders has withstood the test of time. Now Pops can bring those pixelated aliens to the boardroom—and look darn stylish doing it.

Buy it: Amazon

3. Legend of Zelda Flask; $18

A 'Legend of Zelda' flask
Toynk

Saving princesses is thirsty work. Shaped like an NES cartridge, this Zelda-themed flask boasts an 8-ounce holding capacity and comes with a reusable straw. Plus, it makes a fun little display item for gamer dads with man caves.

Buy it: Toynk

4. AT-AT Family Vacation Bag Tag; $12

An At-At baggage tag
ShopDisney

Widely considered one of the greatest movie sequels ever made, The Empire Strikes Back throws a powerful new threat at Luke Skywalker and the Rebellion: the AT-AT a.k.a. Imperial Walkers. Now your dad can mark his luggage with a personalized tag bearing the war machine’s likeness.

Buy it: ShopDisney

5. Flash Skinny Tie; $17

A skinny Flash-themed tie
Uyoung/Amazon

We’ll let you know if the Justice League starts selling new memberships, but here’s the next best thing. Available in a rainbow of super-heroic colors, this skinny necktie bears the Flash’s lightning bolt logo. Race on over to Amazon and pick one up today.

Buy it: Amazon

6. Captain America Shield Apron; $20

A Captain America themed apron
Toynk

Why let DC fans have all the fun? Daddy-o can channel his inner Steve Rogers when he flips burgers at your family’s Fourth of July BBQ. Measuring 31.5 inches long by 27.5 inches wide, this apron’s guaranteed to keep the cookout Hydra-free.

Buy it: Toynk

7. Doctor Who Vortex Manipulator LCD Leather Wristwatch; $35

A Doctor Who-themed watch
Toynk

At once classy and geeky, this digital timepiece lovingly recreates one of Doctor Who’s signature props. Unlike some of the gadgets worn on the long-running sci-fi series, it won’t require any fancy chronoplasm fuel.

Buy it: Toynk

8. Wonder Woman 3-Piece Grill Set; $21

Wonder Woman three-piece gill set
Toynk

At one point in her decades-long comic book career, this Amazon Princess found herself working at a fast food restaurant called Taco Whiz. Now grill cooks can pay tribute to the heroine with these high-quality, stainless steel utensils. The set’s comprised of wide-tipped tongs, a BBQ fork, and a spatula, with the latter boasting Wonder Woman’s insignia.

Buy it: Toynk

9. Harry Potter Toon Tumbler; $10

Glassware that's Harry Potter themed
Entertainment Earth

You can never have too many pint glasses—and this Father’s Day, dad can knock one back for the boy who lived. This piece of Potter glassware from PopFun has whimsy to spare. Now who’s up for some butterbeer?

Buy it: EntertainmentEarth

10. House Stark Men’s Wallet; $16

A Game of Thrones themed watch
Toynk

Winter’s no longer coming, but the Stark family's propensity for bold fashion choices can never die. Manufactured with both inside and outside pockets, this direwolf-inspired wallet is the perfect place to store your cards, cash, and ID.

Buy it: Toynk

11. Mr. Incredible “Incredible Dad” Mug, $15

An Incredibles themed mug
ShopDisney

Cue the brass music. Grabbing some coffee with a Pixar superhero sounds like an awesome—or dare we say, incredible?—way for your dad to start his day. Mom can join in the fun, too: Disney also sells a Mrs. Incredible version of the mug.

Buy it: ShopDisney

12. Star Wars phone cases from Otterbox; $46-$56

Star Wars phone cases from OtterBox.
Otterbox

If your dad’s looking for a phone case to show off his love of all things Star Wars, head to Otterbox. Whether he’s into the Dark Side with Darth Vader and Kylo Ren, the droids, Chewbacca, or Boba Fett, you’ll be able to find a phone case to fit his preference. The designs are available for both Samsung and Apple products, and you can check them all out here.

Buy it: Otterbox

13. 3D Puzzles; $50

3D Harry Potter puzzle from Amazon.
Wrebbit 3D

Help dad recreate some of his favorite fictional locations with these 3D puzzles from Wrebbit 3D. The real standouts are the 850-piece model of Hogwarts's Great Hall and the 910-piece version of Winterfell from Game of Thrones. If dad's tastes are more in line with public broadcasting, you could also pick him up an 890-piece Downton Abbey puzzle to bring a little upper-crust elegance to the homestead.

Buy it: Hogwarts (Amazon), Winterfell (Amazon), Downton Abbey (Amazon)

At Mental Floss, we only write about the products we love and want to share with our readers, so all products are chosen independently by our editors. Mental Floss has affiliate relationships with certain retailers and may receive a percentage of any sale made from the links on this page. Prices and availability are accurate as of the time of publication.

10 Great Father’s Day Gifts to Celebrate Every Kind of Dad

Amazon
Amazon

The very first Father’s Day was celebrated in Washington State on June 19, 1910, and from there, the holiday slowly spread across the country as a regional event. While presidents recognized it on and off, there was never an official, permanent proclamation about the holiday's future until 1972, when President Richard Nixon declared that the federal government would recognize Father's Day on the third Sunday in June from there on out (though it's still not technically a federal holiday.) Initially established as a response to Mother’s Day, and skirting a movement that sought to combine both holidays into a single “Parents’ Day,” Father’s Day has become a day to be celebrated all on its own.

Fathers, grandfathers, and uncles all deserve to be honored on this special day, and that’s why we’ve put together a list of thoughtful gifts to help you say “thank you” to every dad in your life. Whether he’s a grill master, a tech wizard, or a lover of the great outdoors, your dad will love any one of these gifts.

1. Beard Care Kit; $27

A beard kit
FULLLIGHT TECH/Amazon

This beard care kit will keep your dad looking—and feeling—fresh all year long. This set features beard shampoo for cleansing and conditioning, balm for moisturizing and styling, and oil for softening and nourishing. The kit also comes with a comb, brush, scissors, and an eBook on beard care so he can style and maintain his signature look to his heart’s content.

Buy it: Amazon

2. Cuisinart Deluxe Grill Set; $44

Cuisinart grill set on sale at Amazon.
Cuisinart/Amazon

Let dad embrace his inner barbecue master with this 14-piece grill set from Cuisinart. Including a chef's spatula, grill tongs, basting brush, and more, he’ll never have to stress about flipping a burger or cooking the perfect steak ever again. And since the spatula touts a built-in bottle opener, he can enjoy a much-deserved cold one while he gets dinner ready. All the tools fit neatly inside a sturdy carrying case, allowing your dad to bring his tools on the go and be heralded as the king of outdoor cooking wherever he travels.

Buy it: Amazon

3. Wireless Charging Station; $28

A wireless charging station
Seneo/Amazon

Tech dads will rejoice with this wireless charging station designed to charge iPhones, Apple Watches, and Airpods all at the same time. The dock can get all three devices to 100 percent in only three hours, and the phone stand and Apple Watch/Airpods dock can be connected or kept separate for a more streamlined look. The dock can even charge through most cases.

Buy it: Amazon

4. Garmin Running Watch; $230

A running watch from Garmin
Garmin/Amazon

This unique running watch from Garmin will help your dad stay fit, track his miles, and train for that 5K he’s always dreamed of. The watch uses a wrist-based heart monitor to track not just miles, but also stride length, ground contact, balance, and more. And with the built-in, contactless payment chip, your dad can buy a water bottle or protein shake on the road and leave credit cards at home. He can even sync the watch with his phone to receive and respond to text messages, emails, and social media updates while he’s (literally) on the run.

Buy it: Amazon

5. Growlerwerks Growler Keg; $99

A growler keg that's available on Amazon.
GrowlerWerks/Amazon

If you've got a craft beer lover in the family, look no further than this portable growler keg. This growler can store 64 ounces of beer (or kombucha, hard cider, and soda), and all it needs to keep the suds from going flat is a CO2 charger (sold separately). Your dad simply has to fill the growler at his favorite local brewery; select high or low carbonation, depending on what he's drinking; and pull the tap to pour the perfect pint. The keg will keep beverages cold for seven to nine hours, so whether he's going for a hike or a long day at the golf course, he’ll be able to serve up brewery-fresh beverages all day long.

Buy it: Amazon

6. Constitution Tie; $30

Constitution tie on Amazon.
Museum Artifacts/Amazon

History buffs will love this stylish tie inspired by one of the United States’s most important documents: the Constitution. Featuring a screen print of the nation’s founding document with “We the People” featured front and center, this tie will help your dad start up conversations about his favorite Founding Father at social gatherings, rather than going through his well-worn joke book yet again. Each tie is printed on imported silk and hand-finished to give him that personalized touch that he deserves.

Buy it: Amazon

7. Outdoor Tumbler; $30

An OtterBox outdoor mug
Otterbox

For dads who love nothing more than a morning walk—whether that’s around the block or on a hike at the state park—this outdoor tumbler will help him stay hydrated and feeling good until he’s back home. Made with an internal copper lining to keep hot and cold beverages at a consistent temperature, this to-go drinkware will quickly become one of his favorite accessories. It fits most cup holders, so it can travel easily from his favorite lawn chair to the car and back again.

Buy it: Otterbox

8. National Geographic Parks Guide; $19

A guide to the National Parks by National Geographic
National Geographic/Amazon

Fathers with a sense of adventure will be ready for a road trip by the time they’re through with this travel guide from National Geographic. Containing “5000 ideas for the ultimate vacation,” this book includes a comprehensive overview of both the United States and Canada’s best national parks. Including travel tips, planning advice, maps, activity options, and fun facts about wildlife, this book will help your dad embark upon the journey of a lifetime (or simply envision one from the comfort of his back porch).

Buy it: Amazon

9. RCA Wireless Noise-Canceling Headphones; $44

A set of headphones from RCA
RCA/Amazon

Capable of 30 hours of Bluetooth playtime in a single charge, these wireless RCA headphones will let your dad listen to his favorite podcasts, oldies bands, and TV shows all while staying hands-free. With the ability to easily turn the noise-canceling mode on and off, adjust the volume, skip tracks, and answer calls directly from the right ear cup, these headphones make for a great (and easy) listening experience. And at only $44, they’re a fraction of what other wireless headphones cost—but he doesn’t have to know that.

Buy it: Amazon

10. New Balance Trail Running Shoes; Price Varies

A set of sneakers from New Balance
New Balance/Amazon

New Balance sneakers are a signature look for many dads—and for good reason! This 481V3 Trail Running Shoe is designed for both smooth tracks and rough trails, making it a great choice for gym rats and cross-country runners alike. Made from 100-percent leather and textile with cushioned rubber soles, it’s built to pad your dad’s heels while also offering the stability he needs to do the things he does best. With five different colors to choose from, he'll be able to show off his acute fashion sense for many Father’s Days to come.

Buy it: Amazon

At Mental Floss, we only write about the products we love and want to share with our readers, so all products are chosen independently by our editors. Mental Floss has affiliate relationships with certain retailers and may receive a percentage of any sale made from the links on this page. Prices and availability are accurate as of the time of publication.