Why Do Lizards Lose Their Tails and Regrow New Ones?

iStock/Chloe Effron
iStock/Chloe Effron

WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

Many species of lizard lose their tails when they are being chased. When a predator (PREH-duh-tor)—an animal that wants to eat them, like a bird or cat—grabs for the tail, it falls off, and the lizard can run away. How does it happen? Scientists looking at geckos (a type of lizard) under a microscope have found out that some parts of the tail are weaker than other parts.


It’s no accident. The sections of a lizard’s tail will hold together until the lizard is in danger. Scientists think that’s when special cells inside the tail make chemicals that attack the weak points. Then—surprise!—the tail breaks off. It will also keep wiggling for a while to distract the predator while the lizard speeds off. Pretty awesome! That’s not the end of the story, either. Most lizard species can also grow a new tail. 


Lizard tails have a lot of jobs to do. Lizards move their tails around to “talk” to each other. It’s a kind of secret lizard language. The tail also helps lizards keep their balance when they’re scrambling up a tree or jumping from rock to rock. So even though losing the tail is a useful trick, growing it back is pretty important, too. Sometimes lizards can get carried away, though: one busy lizard from Argentina grew six new tails at once!

Watch a gecko regrow its tail in this video


The 10 Best Memorial Day 2020 Sales

iRobot,GoWise,Funko via Wayfair, Entertainment Earth
iRobot,GoWise,Funko via Wayfair, Entertainment Earth

The Memorial Day sales have started early this year, and it's easy to find yourself drowning in offers for cheap mattresses, appliances, shoes, and grills. To help you cut through the noise and focus on the best deals around, we threw together some of our favorite Memorial Day sales going on right now. Take a look below.

1. Leesa

A Leesa Hybrid mattress.
A Leesa Hybrid mattress.
Leesa

Through May 31, you can save up to $400 on every mattress model Leesa has to offer, from the value-minded Studio by Leesa design to the premium Leesa Legend, which touts a combination of memory foam and micro-coil springs to keep you comfortable in any position you sleep in.

Find it: Leesa

2. Sur La Table

This one is labeled as simply a “summer sale,” but the deals are good only through Memorial Day, so you should get to it quickly. This sale takes up to 20 percent off outdoor grilling and dining essentials, like cast-iron shrimp pans ($32), a stainless steel burger-grilling basket ($16), and, of course, your choice of barbeque sauce to go along with it.

Find it: Sur la Table

3. Wayfair

KitchenAid Stand Mixer on Sale on Wayfair.
Wayfair/KitchenAid

Wayfair is cutting prices on all manner of appliances until May 28. Though you can pretty much find any home appliance imaginable at a low price, the sale is highlighted by $130 off a KitchenAid stand mixer and 62 percent off this eight-in-one GoWise air fryer.

And that’s only part of the brand’s multiple Memorial Day sales, which you can browse here. They’re also taking up to 40 percent off Samsung refrigerators and washing machines, up to 65 percent off living room furniture, and up to 60 percent off mattresses.

Find it: Wayfair

4. Blue Apron

If you sign up for a Blue Apron subscription before May 26, you’ll save $20 on each of your first three box deliveries, totaling $60 in savings. 

Find it: Blue Apron

5. The PBS Store

Score 20 percent off sitewide at Shop.PBS.org when you use the promo code TAKE20. This slashes prices on everything from documentaries like Ken Burns’s The Roosevelt: An Intimate History ($48) and The Civil War ($64) to a Pride & Prejudice tote bag ($27) and this precious heat-changing King Henry VIII mug ($11) that reveals the fates of his many wives when you pour your morning coffee.

Find it: The PBS Store

6. Amazon

eufy robot vacuum.
Amazon/eufy

While Amazon doesn’t have an official Memorial Day sale, the ecommerce giant still has plenty of ever-changing deals to pick from. Right now, you can take $100 off this outdoor grill from Weber, $70 off a eufy robot vacuum, and 22 percent off the ASUS gaming laptop. For more deals, just go to Amazon and have a look around.

7. Backcountry

You can save up to 50 percent on tents, hiking packs, outdoor wear, and more from brands like Patagonia, Marmot, and others during Backcountry's Memorial Day sale.

Find it: Backcountry

8. Entertainment Earth

Funko Pops on Sale on Entertainment Earth.
Entertainment Earth/Funko

From now until June 2, Entertainment Earth is having a buy one, get one half off sale on select Funko Pops. This includes stalwarts like the Star Wars and Batman lines, and more recent additions like the Schitt's Creek Funkos and the pre-orders for the upcoming X-Men movie line.

Find it: Entertainment Earth

9. Moosejaw

With the promo code SUNSCREEN, you can take 20 percent off one full-price item at Moosejaw, along with finding up to 30 percent off select items during the outdoor brand's summer sale. These deals include casual clothing, outdoor wear, trail sneakers, and more. 

Find it: Moosejaw

10. Osprey

Through May 25, you can save 25 percent on select summer items, and 40 percent off products from last season. This can include anything from hiking packs and luggage to outdoorsy socks and hats. So if you're planning on getting acquainted with the great outdoors this summer, now you can do it on the cheap.

Find it: Osprey

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.

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.