If you’ve ever spent a long time the bath, pool, or any other body of water, you might have noticed that the pads of your fingers and toes appear “wrinkled” after a while.

You might have wondered why in passing…but did you know it doesn’t happen to everyone?

Keep reading to find out the answers to both of those “whys!”

Many people assume is has something to do with the skin absorbing water, but skin is actually (fun fact) waterproof. Water runs right off of our skin or is easily dried off the surface, which is why we can enjoy being in the water without dire consequences.

Under a microscope, scientists see an unusual arrangement of lipids on skin, in which two hydrophobic tails point in opposite directions.

Typically, the hydrophilic head of a lipid points one way while its two hydrophobic tails point the other. When the tails alternate, the lipids are more tightly packed, which makes skin more resistant to water.

Which is all to say, your wrinkled skin isn’t waterlogged at all.

In 1935, doctors noticed that patients whose median nerve had been severed didn’t get pruny fingers when wet, and subsequently used finger wrinkling as a test for nerve damage. The median nerve is involved in other functions we don’t control, like sweating, and is an essential part of the sympathetic nervous system.

This system puts our body’s systems on alert by raising our heart rate, increasing our respiratory rate, and regulating blood pressure.

The parasympathetic nervous system does the opposite, allowing us to calm down.

But if the sympathetic nervous system makes our fingers wrinkle, what is it trying to prepare us for?

One theory is that they make it easier for us to pick up objects with wet hands, and it tracks as a useful adaptation. The wrinkles not only give us grip, but they act as draining channels that push water out of the way, too.

Our bodies are weird and wonderful things.

I wonder what adaptations they are currently making that we’ll find out about later?

If you found that story interesting, learn more about why people often wake up around 3 AM and keep doing it for life.