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Why Does My Skin Wrinkle in Water?

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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.

Have you ever noticed that your fingers and toes get wrinkled when you’ve been soaking in water for a while? We often call this “prune hands,” because it makes your fingers look shriveled like a prune. (A prune is a dried plum.) The shriveling happens when blood vessels under your skin get narrower. This is caused by your autonomic (Aw-toe-NAW-mick) nervous system. This system keeps your lungs breathing and your heart beating without you having to think about it. 

The wrinkles seem to help us grip and not slip! Look at the bottom of your shoe. Does it have grooves? Those are called treads. The tires on cars and buses have treads too. The water that goes into those narrow grooves gets pushed away. It works the same way with your skin. Water drains from your hands through these grooves. We think this helps us to hold onto objects better. Scientists tested this theory with an experiment. They asked people with wet, wrinkled hands to pick up wet marbles and dry marbles. People picked up the wet marbles faster with wet, wrinkled hands.

Some scientists now think that humans evolved (Ee-VAWLVD)—changed over time—to have this reaction. Being able to hold onto wet things might have helped our ancient ancestors survive. Think about it: if your food lives in a wet place, like a river, ocean, or rainforest, you have a better chance of grabbing it if your fingers “stick” to it. If you are climbing a wet tree, wrinkled fingers might help keep you from falling. Wrinkled toes can help, too. If you’re barefoot, your toes need a good grip in wet or muddy places. 

Want to hear more about the marble experiment? Watch this video from SciShow.


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Animals
Why Do Female Spotted Hyenas Give Birth Through Their Pseudo-Penises?
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YouTube

At the zoo, you can sometimes tell the difference between male and female animals by noting their physical size, their behavior, and yes, their nether regions. Hyenas, however, flip the script: Not only are lady spotted hyenas bigger and meaner than their male counterparts, ruling the pack with an iron paw, they also sport what appear to be penises—shaft, scrotum, and all.

"Appear" is the key word here: These 7-inch-long phalluses don't produce sperm, so they're technically really long clitorises in disguise. But why do female hyenas have them? And do they actually have to (gulp) give birth through them? Wouldn't that hurt … a lot?

The short answers to these questions are, respectively, "We don't know," "Yes," and "OW." Longer answers can be found in this MinuteEarth video, which provides the full lowdown on hyena sex. Don't say we didn't warn you.

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science
Are Sex, Drugs, and Rock 'n' Roll Really Linked? Researchers Investigate
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Steve Wood/Express/Hulton Archive/Getty Images

Around the world, sex, drugs, and rock 'n' roll are said to go hand-in-hand. But do they? As PsyPost reports, a pair of Pennsylvania psychologists recently dove into the empirical evidence tying the three together, asking college students to talk about their drug use, sex lives, and music preferences and talents to suss out whether people who play and enjoy rock music really do have more active sex lives and drug use.

Published in the journal Human Ethnology Bulletin, the study [PDF] of 467 students relied on self-reporting, which isn't typically the most reliable evidence—people are wont to exaggerate how often they've had sex, for instance—but the survey also asked them about their desires, posing questions like "If you could, how frequently would you have sex?" It also asked about how often the students drank and what drugs they had tried in their lifetimes. They also described their musical experience and what kind of music they listened to.

The results were mixed, but the researchers identified a relationship between liking faster, "harder" music and having more sex and doing more drugs. Acoustic indie rock aficionados weren't getting quite as wild as heavy metal fans. High-tempo-music lovers were more likely to have taken hallucinogenic drugs like LSD, for example, and tended to have had more sexual partners in the previous year than people who favored slower types of music. According to the study, previous research has found that attention-seeking people are more likely to enjoy "hard" music.

The study didn't have a diverse enough group either in age or in ethnicity to really begin to make sweeping generalizations about humans, especially since college students (the participants were between 18 and 25) tend to engage in more risky behaviors in general. But this could lay the groundwork for future research into the topic. Until then, it might be more accurate to change the phrase to "sex, drugs, and heavy metal."

[h/t PsyPost]

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