Why Does My Skin Wrinkle in Water?

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.

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.


Study Finds One in Seven Danish Children Will Be Diagnosed with Mental Illness

Kerkez/iStock via Getty Images
Kerkez/iStock via Getty Images

As researchers continue to investigate the origins of depression, anxiety, and other mental disorders, a new study in JAMA Psychiatry has found that one in seven children in Denmark will develop some form of mental illness before they turn 18.

The paper, by researchers at Aarhus University and other institutions, looked at a database of health information collected from 1.3 million Danish children from age 0 to 18. Boys had a 15.5 percent chance, and girls a 14.6 percent chance, of being clinically diagnosed with a mental illness before age 18. Attention-deficit/hyperactivity disorder (ADHD) was the most common disorder among boys, while anxiety was most prevalent among girls. Depression and schizophrenia were also present.

Researchers also examined when children were diagnosed. Boys tended to be labeled with ADHD as young as 8 years old, while girls received the same diagnosis more frequently at 17. Boys were also diagnosed with other illnesses earlier overall.

The study was limited to Denmark, and socioeconomic factors that may influence ailments and diagnoses can vary by country. Still, researchers said these statistics may help mental health professionals prepare earlier intervention and provide young people the help they need.

[h/t Independent]

First-Ever Map of Titan Reveals That Saturn’s Moon Is a Lot Like Earth

NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho
NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho

If there's any life in this solar system outside Earth, we likely won't find it on Mars or even on another planet. Saturn's moon Titan is the place in our celestial neighborhood that's most similar to our own home, and it's where scientists think we have one of the best chances of discovering life. Now, as Nature reports, newly visualized data shows just how much Titan has in common with Earth.

Between 2004 and 2017, the NASA spacecraft Cassini performed more than 100 fly-bys of Saturn's moon. Titan is unique in that it's the only moon in the solar system with clouds and a dense, weather-forming atmosphere. This has made it hard to study from space, but by flying close to the surface, Cassini was able to capture the landscape in an unprecedented level of detail.

Map of Titan.
The first global geologic map of Titan.
NASA/JPL-Caltech/ASU

NASA's new map of Titan, published in the journal Nature Astronomy, reveals a varied world of mountains, valleys, plains, and sandy dunes that starkly contrast with the desolate wastelands we've seen on neighboring planets. It's also home to seas and lakes, making it the only place in the solar system other than Earth with known bodies of liquid. But instead of water, the pools mottling the moon's surface consist of liquid methane.

Even with its Earth-like geology and atmosphere, chances of finding life on Titan are still slim: Temperatures on the surface average around -300°F. If life does exist there, it's likely limited to microbes in the moon's craters and icy volcanoes.

It will be a while before NASA is able to study Titan up close again: NASA's next drone mission to the body is set for 2034. Until then, scientists have plenty of data recorded by Cassini to teach them more about how the moon formed and continues to change.

[h/t Nature]

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