What are fingerprints good for, besides aiding police investigations? That’s the question that biomechanics researcher Roland Ennos recently set out to answer. This notion that human fingerprints (and presumably footprints) evolved because they act like tire or boot tread–increasing the friction against a smooth surface so we don’t slip or drop stuff–is a 100-year-old urban myth that, apparently, had never been put to the test [NPR].
To test the impact of fingerprints, Ennos rigged a machine that measured the amount of friction generated by a fingertip (belonging to study coauthor Peter Warman) when it was pressed against a piece of acrylic glass. Warman gradually increased the pressure, going from a light touch on the glass to a tight grip, but the corresponding friction didn’t increase as much as the researchers expected. Soon they realised that the skin was not behaving like a normal solid, where friction is proportional to the strength of the contact. Instead, it was behaving like rubber, where the friction is proportional to the contact area between the two surfaces [BBC News].
Explains Ennos: “Because there are all the gaps between the fingerprints, what they do is reduce the contact area with the surface.” … Measurements taken from ink marks then revealed that fingerprints actually reduce the area in contact with a surface by about one third, compared with smooth skin. Therefore fingerprints actually reduce friction [New Scientist]. The study appears in the Journal of Experimental Biology.
But if fingerprints don’t help us keep a grip, what do they do? Ennos suggests that fingerprints may allow our skin to stretch and deform more easily, protecting it from damage. Alternatively, they may allow water trapped between our finger pads and the surface to drain away and improve surface contact in wet conditions. Other researchers have suggested that the ridges could increase our fingerpads’ touch sensitivity [BBC News], possibly by amplifying the vibrations caused when a fingertip sweeps over a finely textured surface.
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Image: flickr / kevindooley
June 15th, 2009 at 6:36 pm
It could also be that the ridges of our fingerprints deform in order to improve contact, and thus grip, with rough surfaces. I would say our ancestors had much more experience with rough objects than smooth and the improved grip on rocks and branches represented an evolutionary advantage.
Also, no mention of the role of calluses in the equation.
Also, an “n” of one? Really?
June 16th, 2009 at 6:37 am
Several years ago I tore a fingernail off. Until it grew back, I lost my ability to grip things with the finger in question. Having fingerprints was no help at all. I think it’s the nails that give our grip strength. When, in the course of work, I accidentally cut a fingertip, I experience a kind of creepy loss of tension. Maybe that means something.
June 16th, 2009 at 9:19 am
…however in the end the species died out; for even with their grip enhancing fingerprints they were still unable to scale the acrylic tree and fetch themselves some bananas to eat.
June 16th, 2009 at 5:59 pm
“When, in the course of work, I accidentally cut a fingertip, I experience a kind of creepy loss of tension.”
endorphin response to injury, maybe?
June 16th, 2009 at 11:31 pm
The ridges could also help form a type of minuscule vacuum that could aid in grip. Ever notice when your hands are just a little bit sweaty it is much easier to grip things and they almost seem to stick. This small amount of moisture could be creating an air tight seal that could only be made possible through ridges or suction cups….we just happen to have ridges. I have to call BS on this article.
June 17th, 2009 at 6:56 am
Interesting stuff…
I think the title & debate about this research is a bit misleading, for fingerprints have multiple ‘effects’:
The research has described that our skin behaves like RUBBER, which implicates that CONTACT SURFACE is needed to enhance a grip. And because of the ridges of the fingerprints (bumbs and holes) the contact surface is about 33% lower compared to a flat skin. In that sense the fingerprints to not provide a positive effect on our hand grip.
However, Roland Ennos also stated that fingerprints are likely to sort of protect the skin: the prevent the process of blistering. And in that sense fingerprints are very important for the efficiency of our hand grip!!
You can read more details + quite a few quotes from the researcher in the following article:
http://www.handresearch.com/news/fingerprints-unlikely-increase-hand-grip-friction.htm
Including a podcast with a Roland Ennos interview about his findings!
Thanks for the discussion + greetings from The Netherlands,
Martijn.
June 17th, 2009 at 5:08 pm
Perhaps fingerprints are there so that we can control the amount of friction produced. Depending on how hard one presses it is easy to imagine that this effects the ridges. This could control how much skin is actually in contact with the surface, and thus how much friction is experienced.
July 23rd, 2009 at 5:04 am
You all are way off base on this one…..The function of Fingerprints is to remove cellular waste deposited om the skin by the lymphatic system.