Why do we have fingerprints? We have fingerprints to help us grip and to help us feel things.
We all have fingerprints on our fingers that are made up of swirls and creases in the skin of our fingers. All primates have fingerprints, which goes a long way to showing how useful they are for grip. You can test this for yourself. Put chalk dust or talcum powder on your fingers and then try to pick something up. If the dust fills the creases in your fingers, it becomes very hard to grip things. We have fingerprints so that we can grip. Primates have fingerprints so that they can climb more easily. Interestingly, climbers actually use chalk when they are climbing. This is, however, just to dry the sweat off their fingers and make sure they don’t slip.
It is said that all fingerprints are unique, and this is mostly true. It is estimated that your fingerprint is a 1 in 6.4 billion. That is so large as to be almost unique. If you consider the law of large numbers, it is possible that someone with the same fingerprints as you has been alive at some point, but the chances of them being alive right now are slim. One interesting thing is that the difference in fingerprints is not just in how the fingerprint on my thumb differs to your thumb, but how the fingerprint on my thumb differs to my middle finger. All of the fingerprints on our hands are different and this combination makes my hand unique. Fingerprint analyzers have always looked at the branches and the endpoints on fingerprint ridges to compare fingers and they have always said that even two fingers on the same hand are unique. This was put to the test recently and found to be not quite true. An AI system was trained on a database of 60,000 fingerprints. It was then able to identify if fingerprints were from a different finger of a person already in its database with a 77% success rate. It turned out that the AI system was looking at the angles and the curvatures of the swirls and loops in the center of the fingerprint. Our prints might be different, but one person has extreme similarities here across the fingers.
Fingerprints help us grip and that is also why we have prints on our toes. We don’t use our toes so much anymore, but there are a lot of primates that do. The grip our fingerprints offer can also be seen in more depth after a bath. When we are in the bath for a long time, our fingers become all wrinkly and the ridges of our fingerprints are much more pronounced. This is to aid us gripping things in the wet. Presumably, it would have been useful to have this ability when we were climbing trees, and it was raining. It was thought that this happened when the outer layer of the skin absorbed a lot of water from the bath. In actual fact, that is not the case. The wrinkles appear because of a reaction in the body’s autonomic nervous system that makes the blood vessels contract below the skin. Water is the trigger for it, but water is not the cause. The shape of the fingerprint creates channels for the water to go through, almost like a car tire.
Our fingerprints also help us to feel things as well. We have nerves all over our skin, but in our fingers the nerves on the outside of the fingerprint touch a surface before the nerves on the inside of the fingerprint. The nerves in the depths of the fingerprint are actually very responsive to vibrations. When we move our fingers over a surface, the edges of the fingerprint slide over the surface and make imperceptible vibrations that the nerves inside the fingerprint can pick up. These vibrations would be slightly different depending on the texture of the thing we were touching, and they give us a far more detailed sense of touch.
Our fingerprints are decided by our DNA, but also how fast our fingers grow, what we eat, and a whole host of other things. They start forming in week 12 of an embryo’s development. The ridges of the fingerprint go down through the top layer of skin, and they regrow in the same way as all the rest of the skin. You can burn your fingerprints off, but they will always grow back the same way. If you really wanted to hide your fingerprints, then scarring would be the only way. And this is what I learned today.
Photo by cottonbro studio: https://www.pexels.com/photo/close-up-photo-of-fingerpints-on-paper-8382611/
Sources
https://www.bbc.com/news/magazine-19740979
https://www.ojp.gov/pdffiles1/nij/225321.pdf
https://www.livescience.com/why-do-humans-have-fingerprints.html
https://www.scientificamerican.com/article/why-do-our-fingers-and-toes-wrinkle-during-a-bath
https://www.sciencefocus.com/news/fingerprints-not-unique-ai
https://www.the-scientist.com/finally-scientists-uncover-the-genetic-basis-of-fingerprints-70983