Scientists Wonder What Fingerprints Are For

Hugh Pickens writes "The BBC reports that scientists say they have disproved the theory that fingerprints improve grip by increasing friction between people's fingers and the surface they are holding. Dr Roland Ennos designed a machine which enabled him to measure the amount of friction generated by a fingerprint when it was in contact with an acrylic glass at varying levels of pressure. The results showed that friction levels increased by a much smaller amount than had been anticipated, debunking the hypothesis that fingerprints provide an improved grip. Ennos believes that fingerprints may have evolved to grip onto rough surfaces, like tree bark; the ridges may allow our skin to stretch and deform more easily, protecting it from damage; or 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."

Comments

Primates

[MichaelSmith]

I noticed this at the zoo watching a bunch of monkeys swing from branch the branch in a cage. The tree branches they had been given had been worn smooth through long use and every time a monkey grabbed on to a smooth branch I felt a jab in my fingers in sympathy. There is something bad about grabbing a smooth object and relying on it to save your life.

So maybe finger prints improve grip with smooth timber surfaces. Testing against glass doesn't sound very realistic. We didn't evolve to grip glass. Or maybe (as the summary suggests) it is something to do with detecting the texture of a surface to find a place to grip.

Of course they don't ask why people have unique finger prints. Maybe it evolved to make murderers easier to catch.

Re:Primates

[Threni]

The fingerprints we have now may be little use for increasing friction, but perhaps at some point in the past before they'd evolved away they'd have been been more pronounced, and would have trapped sticky dirt within more efficiently than todays generally cleaner hands.

Re:Primates

[jonbryce]

Or maybe it didn't evolve that way for any particular reason.

These sort of studies assume we have now evolved to perfection. But that suggests there will be no further evolution, which I don't think is the case.

Re:Primates

[Anonymous Coward]

"Of course they don't ask why people have unique finger prints."

What are the other unique features? Vein patterns and eye color patterns are as unique as finger prints. The odds are the uniqueness is a function of growth unrelated to purpose.

Re:Primates

[daymitch]

This doesn't follow (that there should be folks without fingerprints if they have no purpose). It depends on the genetic basis of fingerprints and the genetic history of our species.

One thing we have learned about human genetics is that the human population went through several 'bottlenecks' where the population was reduced to low numbers. Is this what you are referring to?

It's a process called genetic drift. My old botany prof described it with a fun story. Imagine some disaster that reduces the entire human species to a small group on a raft. Everyone is dark-skinned except for Gunter, a blonde-haired, blue-eyed nordic type. Gunter trips and falls off the raft and gets carried away by the current (he drifts away, get it).

It's an accident that has nothing to do with his reproductive potential. Anyone else could just as easily have had the same accident. If they had, the genes for blonde-hair and blue eyes would still be in the human population and human evolutionary history would be different in that respect. Small population sizes increase the importance of drift.

Of course, other factors come in to play when you imagine the difficulties a fair skinned guy would have on a raft relative to other human types. That's another story.

ummm where did captain obvious go?

[meow27]

"Other researchers have suggested that the ridges could increase our fingerpads' touch sensitivity."

from TFA (sorry i can figure out how to use the quote function :/)

how is this not obvious? where he have some sort of ridge like pattern (hands, feet) we have more sensitive nerves there. The ridges increase surface area of our skin which means we can feel more using up less volume

the star nosed mole is the perfect example of increased surface area for more touch sensitivity.

Re:Maybe they're for nothing?

[digitig]

Careful with "purpose" -- Evolution is non-teleological, and "purpose" has no place in evolutionary explanations. I think you mean that everything has to ba adaptive, but even then I wonder how you know -- surely evolution would allow characteristics that are not adaptive as long as they have no cost. In fact, evolution depends to some extent on things that are not necessary, as Stephen J Gould pointed out -- a part of an organism can only adapt to a new function if it's not needed for something else.

It's wet grip

[R2.0]

I've had the experience of having no fingerprints for a time. I worked at UPS unloading trucks; one of the customers shipped many thousands of small boxes just before the end of the year; the boxes were the precise size that the only way to grip them was with the pads of fingers and thumb (I'm looking at you, Daytimers!). A large portion of those boxes passed through my hands. Shortly after I started work there, I noticed that I was having trouble gripping items that were wet - a water glass with condensation on it would routinely slip through my fingers. When I examined my hands I saw that the ridges of my fingerprints were basically worn away. I wore gloves for a bit while working and the problem cleared itself up.

Another illustration would be to look at the skiving on the bottom of a pair of deck shoes. On a dry surface, they offer no advantage whatsoever, but on a wet surface the difference in grip is remarkable. Or for that matter tire treads - a set of slicks is the absolute best way to maximize grip - unless it's wet, at which point they become the WORST configuration.