Why do we have fingerprints?

21 September 2009
Presented by Diana O'Carroll.

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Just what is the point to all those ridges and furrows set into our fingers, toes, palms and soles? We do some detective work on the answer. Plus, we ask how sharks make blood when they have bones made from cartilage.

In this episode

Fingerprint

00:00 - Why do we have fingerprints?

Fingerprints are all well and good for finding out whodunnit, but why have they evolved?

Why do we have fingerprints?

We put this question to Dr Roland Ennos from the University of Manchester...Well, the answer, I'm afraid, is that no one truly knows. The most obvious idea is that they roughen our fingers to increase the friction. But we've done some test here in Manchester and we found that in fact the fingers actually behave rather like car tyres and because the fingerprints reduce our contact areas with a surface, they will actually reduce friction, just like the grooves in car tyres in a wet weather tyre and reduces the grip of the formula one car. Another possibility which I must say I favour, is that the ridging could actually help to prevent blister formation because the pattern will allow our skin to have much greater compliance and so that can help to reduce the sheer stresses around the edge of our contact zone. And the reason I believe is that if you ever do DIY tasks, what you tend to find is that the only bits where you get blisters is the bits, not on your fingerprints or wherever the big pattern of your palms, but in areas where there aren't any prints. Well, of course there is no doubt that one of the roles the fingerprint must be to improve tactile discrimination because rubbing you finger over a surface, when it hits the rough projections they seem to help to detect vibrations and so, it is likely that one of the roles of finger prints is to improve touch discrimination. But that can't be the main function because the soles of our feet, the palms of our hands also have finger prints. So, that must be just the secondary function.

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