Who knew this would be such an interesting question? I was expecting a pretty simple answer, but it seems there is a lot to wrinkly finger syndrome, and some scientists even call it a mystery.
Here goes, as I understand it.
Our skin is covered in an oil called sebum (love telling that one to kids...hehehe, sebum!) which gets washed away when we soak too long.
Hands and feet get a lot of use so contain a lot of dead keratin cells, which is the matter found in hair and nails. Without the sebum, the dead keratin cells absorb water and the outer layer of skin swells. Because this skin is attached to the tissue beneath it, the extra surface area causes it to wrinkle.
Simple enough, but this is just a theory.
Another theory hypothesized by scientists at Newcastle University says the wrinkling is caused by the constriction of blood vessels beneath the skin. This seems to be an automatic function of the nerve fibres beneath the skin, which are triggered to shrink when hands are immersed. This constriction causes the skin to be pulled inwards, thus wrinkling it. This theory is backed up by the fact that people with nerve damage to their hands will not display wrinkly finger syndrome, even after a long relaxing bath.
So why would our bodies require such a function? Well, this is where it gets interesting. Newcastle University puts it down to a survival mechanism that allowed our ancestors to gather food in the wet. The wrinkles act like the tread on car tyres, providing some traction. They also create channels, allowing water to drain off the fingers, again improving grip.
This was tested using marbles. People with wrinkly fingers can grasp a wet marble better than those who haven't been soaking. The grasping of dry marbles was not improved.
How do I explain this to my kid?
Yes, perhaps a bit too much science? I would start with the sebum. The nerves would need to be explained before you continued on. Talk about how you can feel something is hot or cold, rough or smooth, etc. Then move on to the car tread and the channels and the gripping of wet vegetables in the rain. That should keep em quiet for a while.
I have news
Today my two-year-old asked if the neighbour's cat could come in the car with us to the playground. I said, no, cats don't like cars. He said....wait for it....WHY?
His first why. I'm so proud. And scared.
In two weeks
No, my next question is not why don't cats like cars. What I would like to know, and this may be a really simple one, but I'm a gonna do it anyway, is: why do we call the western world, western and the eastern, eastern?
