Watch any detective show on TV and you know they will prove the guilt or innocence of the suspect if clear fingerprints were found at the crime scene. Fingerprints are unique identifiers and are not the same in any two people. Even identical twins have different fingerprints. We rely on fingerprinting as a method for security identification but until recently, it was never clear why we even have fingerprints. Now researchers have come up with a plausible purpose for these swirls and whirls that cover our fingertips and toes.
For over 100 years, it had been assumed that fingerprints provided our hands with more traction when picking up slippery objects. It was thought that the grooves on our fingertips increased the surface texture our fingers feel and permitted better grip since smooth surfaces are more difficult to grasp. This determination came from the observation that certain primates, such as koalas, have fingerprints and climb trees so their fingerprints must assist them in grabbing slippery limbs.
The theory that fingerprints increased grip was recently disproved by researchers at the University of Manchester in England through a method of testing the friction level of fingertips rubbed over an acrylic glass called Perspex®. Repeatedly, the researchers found that the friction amounts measured were less than expected until more and more of the finger was pressed against the Perspex®. The researchers reasoned that fingerprints actually were preventing more of the surface area of the finger from coming in contact with the object and even could conceivably act to loosen rather than increase grip. Based on the researcher’s results, less contact occurs to objects being touched so fingerprints can not increase our ability to hold them and do not allow us to have a tighter grasp.
So if fingerprints don’t help us have a better grip, then what do fingerprints do?
The grooves on our fingerprints are instead believed to increase our sense of touch through vibration. Our fingertips are loaded with specialized nerve endings called Pacinian corpucles that detect changes in the texture of objects.