Hey everybody, welcome back to Explain My Confire. The podcast where we take the questions you always wanted to ask and talk about them in a way that's easy to understand. We are your hosts, I'm Tim. I'm Kevin.
So Kevin, ever been in a swimming pool too long and ended up with wrinkly fingers? Well, of course. Many times, all the time. Pruney fingers, or they even call it water-aging sometimes.
That's right. So the question today is, why do out-fingers and toes wrinkle after being in water for too long? Is it because water makes our skin swell? And why don't we notice this in other animals?
Hey, that's the common assumption, isn't it? That wrinkling is that result of water passing in to the outer layer of the skin and kind of making it swell up. But you know, researchers have found that this assumption could be false. You've got to explain this.
How did they figure this out and what did they observe? So doctors studied patients with injuries in which the median nerve had been severed, had different reactions. Now, the median nerve is one of the very main nerves running through the arm and down to the hand. And so what they noticed was that the fingers of these patients, they did not develop the wrinkles when it submerged in the water.
So today, they even used this to medically test nerve damage. Ah, yes. It's the reverse effect, the wrinkle test. That's right.
It's called the wrinkle test, or sometimes O-Rions or Lukensen's wrinkle test. It's a test of peripheral nerve function. And so what happens is that doctors, they place a patient's fingers in warm water for approximately 10 minutes. And if the fingers do not wrinkle, well, this is a sign that their nerves are probably damaged.
I see. So how do we put this all together? What does this mean then? Well, what this means is that the change in our skin, the wringling, is actually a reaction from the body's autonomic nervous system.
The system that also controls our breathing, our heart rate, and perspiration. You see, the median nerve helps control so-called sympathetic activities such as sweating and the constriction of blood vessels. So what all it means here is that the distinctive wrinkling in our fingers is purposely caused by blood vessels contracting below the skin. It's essentially our nervous system controlling the wrinkling.
And it was actually in 2011, a evolutionary neurobiologist in Boise, Idaho named Mark Changizi and his colleagues suggested that if wrinkling is an active process, it must therefore have an evolutionary function. So that would mean that there's a reason behind this function. What purpose does having wrinkles actually serve? Yeah, so scientists think that the answer is that wrinkles help to improve our grip when our hands get wet.
There's even a paper in the journal Nature, which we can link to in the show notes, and the channels that basically produce the wrinkles help water to flow away from the point of contact between the fingers and the object. So finger wrinkles might have evolved to really help us grasp wet objects and surfaces. Actually, more recently, even in 2020, there was a study of gripping efficiency that found that wrinkles decreased the force required to grip wet objects by something like 20%. So this would also help support that traction hypothesis.
Fascinating. Now, turning to a practical question, then how long does it take for your skin on your fingers to wrinkle when they're in water? Oh, well, actually anybody can try this out and test this at home, but I'll give you the short answer. It depends on the temperature.
It actually only takes a matter of seconds in hot water, like the water may be coming out of a hot shower bath. But at some cooler temperatures, it can take up to 10 minutes for you to start observing wrinkles. Most studies on this topic have shown that it takes about 30 minutes in the water for maximum wrinkles. Another interesting observation is that it often takes women longer to develop wrinkles under fingers and men.
The effect itself, though, is only temporary. Our fingers do return to normal after 30 minutes or so. So if there were benefits, evolutionary benefits, why not just have permanently wrinkled fingers? That's also a really good question.
And we don't really know exactly. Some people have said it because fingers are less sensitive in their pruning state. It's such a simple thing and simple question on the surface, but it turns out there are lots of unexplained circumstances and things that the scientists are still looking into. Plenty of medical research still being done in this area.
That's right. That's right. In fact, scientists are investigating how our wrinkling characteristics might be a good indicator for our more than just things like nerve damage. You know, there are links to a wide range of conditions, including cystic fibrosis, Parkinson's, and type 2 diabetes, where how we wrinkle might be able to give us early indications of those conditions.
So we'll definitely have to keep watching the space. We will indeed. Did you learn something new? If you did, send us an email.
We are at ely5.com. We love hearing from you, especially when you've got suggestions for us on future topics. As always, thank you to the community at r-explainlac.com and we will see you all next week.