How did I get my own unique set of fingerprints?
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How do we get the fingerprints we have? – Oscar V., 8 years old, Somerville, Massachusetts
Fingerprints are those little ridges on your fingertips. These are essentially folds of the outer layer of the skin, the epidermis. The “footprints” themselves are the patterns of skin oils or dirt that these ridges leave on a surface you have touched.
Your fingerprints started forming before you were born. When a fetus begins to grow, the outer layer of its skin is smooth. But after about 10 weeks, a deeper layer of skin, called the basal layer, begins to grow faster than the layers above it, causing it to “curl” and bend. The expanding bottom layer ends up crumpled and bunched under the outer layer.
These folds eventually cause the surface layers of the skin to wrinkle as well, and by the time the fetus reaches 17 weeks of age – about halfway through pregnancy – its fingerprints are set.
Although this folding process may seem random, the overall size and shape of fingerprints is influenced by the genes you received from your parents. So you probably share some fingerprint patterns with your family members.
But the details of your fingerprints are influenced by many factors other than genes. For example, the shape and size of the blood vessels in your skin, the rate at which the different layers of skin grow, and the chemical environment inside the uterus all play a role. No two people end up with exactly the same fingerprints, even identical twins.
It was only in 2015 that a large long-term study showed that fingerprints are stable throughout a person’s life. The ridges of a fingerprint are visible on the surface layer of the skin, but the pattern is actually “coded” underneath. Even if you have a serious skin injury, your prints will return when the outer layer heals – although you may also have a scar.
Your fingerprints are therefore completely unique to you and were so before you were born. No matter how much you change as you grow, you will always have the set you have now, no matter how long you live.
What is the point of a fingerprint?
Surprisingly, no one really knows what fingerprints are for.
People have long thought that fingerprints provide the friction that helps our hands grip objects. This makes sense because other animals besides humans that have fingerprints – including many other primates like monkeys and koalas – are all tree climbers.
But sometimes what makes sense isn’t true, and a recent study found that fingerprints don’t really help people retain objects — at least, not objects with smooth surfaces.
Other possibilities are that fingerprints enhance your sense of touch or help protect your fingers from injury. But scientists don’t yet know for sure.
Use your prints
Police have used fingerprints and their unique loop, whorl and arc shapes to help catch criminals for more than 2,000 years, dating back to ancient China.
Fingerprints are now used for many other purposes, all based on the fact that each person’s fingerprints are different. You can use this unique code to unlock your phone or enter a restricted area, for example. In Malawi, fingerprints were used to identify farmers who took out loans. They can even be taken from babies and used throughout the person’s life to access their vaccination records.
Police forces also continue to find new uses for fingerprints. As methods of detecting and studying fingerprints have improved, detectives can even use them to see who threw a particular rock. These small ridges can also hide tiny amounts of substances, meaning they could be used to detect the use of illegal drugs like cocaine and heroin. And now forensic scientists can also detect decades-old fingerprints – perhaps allowing detectives to solve very old crimes – thanks to a new technique that uses a color-changing chemical to map the sweat glands of your fingerprints.
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This article is republished from The Conversation, an independent, nonprofit news organization that brings you trusted facts and analysis to help you make sense of our complex world. It was written by: Sarah Leupen, University of Maryland, Baltimore County
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Sarah Leupen does not work for, consult, own shares in, or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond her academic appointment.
