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Although fingerprints are incredibly useful for identifying criminals, scientists still don't fully understand their biological function. However, as they continue testing various hypotheses, they’re getting closer to discovering the true purpose—and uncovering some fascinating details in the process.
Could They Enhance Our Tactile Sensitivity?
In a 2009 study, researchers from the Ecole Normale Superieure in Paris developed two biomimetic tactile sensors that replicate the human ability to sense and perceive texture. One sensor had grooves mimicking fingerprints, while the other was smooth, like unmarked skin. When tested on textured surfaces, the fingerprinted sensors generated vibrations up to 100 times stronger than the smooth ones. These vibrations, the scientists found, were governed by a frequency in the optimal sensitivity range of the Pacinian corpuscles—receptors in our skin responsible for detecting pressure changes and vibrations. The researchers speculate that fingerprints may help amplify certain tactile sensations, making them easier for the nervous system to process. They also suggest that the unique swirling patterns of fingerprints ensure that some ridges consistently glide sideways across surfaces, regardless of the direction of movement, aiding the generation of vibrations.
Do Fingerprints Help Us Grip Better?
Humans, apes, monkeys, and koalas all have fingerprints. Some New World monkeys even possess ridged pads on their tails that help them grip trees. The presence of fingerprints across these species has led some to speculate that they are an adaptation to improve grip when climbing or manipulating objects. However, there is limited experimental evidence to support this idea. In 2009, biomechanicists at the University of Manchester tested this theory and found that fingerprints may not actually enhance grip. Dr. Roland Ennos and his student Peter Warman examined the grip strength of Warman's fingers at different angles on sheets of acrylic glass. The results showed that friction did not increase as expected when more pressure was applied. In fact, the grooves between the ridges of fingerprints reduced the contact area with the glass by about one-third compared to smooth skin, resulting in less friction and a weaker grip.
What Other Theories Are There?
Ennos and Warman offer several alternative hypotheses for the function of fingerprints in their paper. These include the idea that fingerprints help our skin conform more easily to the objects we touch, reducing shear stress and preventing blisters; that the ridges increase friction on rough surfaces by fitting into surface depressions, thus providing a larger contact area; and that they might help water run off, much like tire treads. Ennos has stated that his lab is investigating these theories further, though no results have been published yet.
