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Medicine Science

Scientists Wonder What Fingerprints Are For 347

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."
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Scientists Wonder What Fingerprints Are For

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  • Primates (Score:4, Interesting)

    by MichaelSmith ( 789609 ) on Sunday June 14, 2009 @08:17AM (#28325855) Homepage Journal
    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.
  • by meow27 ( 1526173 ) on Sunday June 14, 2009 @09:01AM (#28326005)
    "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:Primates (Score:3, Interesting)

    by Threni ( 635302 ) on Sunday June 14, 2009 @09:05AM (#28326035)

    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.

  • by digitig ( 1056110 ) on Sunday June 14, 2009 @09:09AM (#28326047)
    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.
  • Re:Primates (Score:4, Interesting)

    by jonbryce ( 703250 ) on Sunday June 14, 2009 @09:30AM (#28326129) Homepage

    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.

  • by jonbryce ( 703250 ) on Sunday June 14, 2009 @09:32AM (#28326143) Homepage

    My view is that the reason science and religion come up with different answers is because they ask different questions.

    Science can tell you how to create a bomb that will kill lots of people. Religion can try to tell you whether or not creating such a bomb is a good idea.

  • my guess (Score:2, Interesting)

    by purpleque ( 948533 ) on Sunday June 14, 2009 @09:38AM (#28326173)
    I am going to go with...They are for increasing touch sensations on the fingertips to increase detection of differences and variations in textures of objects.
  • by Anonymous Coward on Sunday June 14, 2009 @09:50AM (#28326225)

    My view is that the reason science and religion come up with different answers is because they ask different questions.

    Q: What makes a rainbow?

    Science A:A rainbow is an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth's atmosphere. They take the form of a multicoloured arc, with red on the outer part of the arch and violet on the inner section of the arch. The light is first refracted as it enters the surface of the raindrop, reflected off the back of the drop, and again refracted as it leaves the drop. The overall effect is that the incoming light is reflected back over a wide range of angles, with the most intense light at an angle of 40 - 42 degrees.

    Religion A:It's a sign of God's promise to Noah to never again flood the earth. (Genesis 9.13-15)

    Science, to me, is about observing the world, and hopefully learning something. Religion seems to be about accepting answers from thousands of years ago without questioning their merit.

  • by Nirvelli ( 851945 ) on Sunday June 14, 2009 @09:56AM (#28326265)
    But the appendix isn't on its way out, it's there for after you've had diarrhea. []
  • by somersault ( 912633 ) on Sunday June 14, 2009 @10:19AM (#28326393) Homepage Journal

    The only difference between you and someone who doesn't understand logic is.. almost exactly nothing. Science doesn't require irrational belief, it is simply based upon more and more thorough observation and testable hypothesis', while religion is based upon shallow observation and wishful thinking.

    The key difference to me between religion and science is that religious folks have to explain all new observations in such a way that it will fit into their current worldview, because they are terrified that conflicting ideas will mean their god doesn't exist. Most Christians in my family are terrified to look more into evolution, with the only time they view anything on it being when they read Christian articles to reassure themselves that it isn't true without doing any research. Scientists will simply say "oh well we were wrong about that, now we can record this new and more accurate understanding of things and keep working to understand even more". They do not let irrational fears restrict their thinking.

  • Re:Primates (Score:3, Interesting)

    by Anonymous Coward on Sunday June 14, 2009 @10:20AM (#28326399)

    "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.

  • Sexy (Score:3, Interesting)

    by Demonantis ( 1340557 ) on Sunday June 14, 2009 @10:44AM (#28326507)
    Fingerprints might not have any use. There could be a multitude of reasons why people have them. People could find them sexy or fear anyone that doesn't have them. They could simple be a by product of another mutation that benefited humans. Evolution is a fun random thing without any real directional purpose. Some times yes mutations are beneficial other times not. People have a lot of trouble understanding that.
  • by yttrstein ( 891553 ) on Sunday June 14, 2009 @11:08AM (#28326617) Homepage
    Right, or you can just ask someone with no fingerprints, like my uncle who went through a certain kind of auto-immune chemo treatment which caused his fingerprints to peel away permanently over the course of several months.

    He says his fingertips are no longer nearly as sensitive to heat and cold, and his ability to identify different sorts of rough surfaces has diminished severely; he can't tell the difference between rubber and suede for example without looking now.

    I'm sure he'd be willing to have a phone call with an inquisitive scientist, should there be any out there who also have a well developed sense of the obvious.
  • by johnsonav ( 1098915 ) on Sunday June 14, 2009 @11:58AM (#28326857) Journal

    Assuming they are correct ( its still just a theory ), as the human race continues to advance the need would be reduced and eventually eliminated, so ya, it should be 'evolved out' of the species.

    What is the selection pressure? The places people live with better sanitation (reducing the need for an appendix), are the same ones where appendicitis is a treatable condition; so it's more or less a wash.

  • by Anonymous Coward on Sunday June 14, 2009 @12:43PM (#28327203)

    I think we'd want to look at the methodology too. Something is odd about this one.

    I worked a while with a chap who'd worn his pads smooth from his day-job making elm & maple baskets. He had trouble with wrenches. There'd be a regular clank from a dropped wrench in the shop, and he'd have to curl his fingers around them more to pick up. Couldn't do the usual 'tip-grip' that you and I do to pick up a steel wrench. Ditto sockets, rulers, pens, and the like. There was nothing else odd about the chap, and he used to work as a mechanic without the trouble. The slippage was just an annoyance that came along after the wear problem.

    I have a similar problem with one little finger where I destroyed the pad on a belt sander, and had a smooth section grow back. The un-printed area is slick. Can't really call it scar tissue anymore because that was about fifteen years ago. There's just no pad because the sides had to grow together in place.

    Maybe there's a difference with pure flat surfaces dragged in Dr. Ennos's method, as opposed (sorry) to pressing the pads around a curved smooth surface? Maybe subtle surface moisture and dust content comes into play? Kudos to Dr. Ennos for applying science, but I suspect this experiment isn't going to be the last word, but rather an interesting start of a direction of inquiry.

  • It's wet grip (Score:5, Interesting)

    by R2.0 ( 532027 ) on Sunday June 14, 2009 @03:06PM (#28328173)

    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.

  • Re:Primates (Score:3, Interesting)

    by daymitch ( 699517 ) on Monday June 15, 2009 @12:58AM (#28331979)

    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.

  • by Nate4D ( 813246 ) on Monday June 15, 2009 @03:49AM (#28332741) Homepage Journal
    Science requires a belief which there is no way to prove, which is that what you sense is reliable.

    In your view, does a belief have to be provable to be rational?

    In a less philosophical vein, faith in scientific approaches requires a belief that the universe is predictable ("If we do X a bunch of times, and get result Y, it's reasonable to expect that we'll see result Y the next time we do X.").

    That's actually a large (and unprovable) assumption, as many philosophers will happily tell you. Of course, by definition, an assumption is unprovable. Call it a postulate or an axiom, if you prefer, but it's still the same thing - something you take for granted, and acknowledge you cannot prove.

    In the end, scientific methods are anything but logically rigorous. The whole system of science is predicated on a method of argument that is considered fallacious in formal logical arguments.

    Are scientific approaches useful? Definitely. Forming hypotheses based on what you see, then testing them is an extremely pragmatic tool for getting through life, and also for developing technology and building mental models of how things seem to work.

    Don't mistake it for a logical tool, though. I guess it's fine to call it rational, if your definition of rational doesn't require logical rigor. Mostly, though, I think the word "reasonable" is used to describe something that seems intuitively correct based on observation, not "rational". Maybe it's just my social circle that uses it that way, though.

    All human beings have a strong tendency to explain new observations in a way that it fits into their current worldview. We call it confirmation bias, and in some contexts, it can be a problem.

    While confirmation bias is not logically rigorous in the least, it can actually be a pragmatic tool for going through life. I've never met anyone whose life philosophy was completely bulletproof - if you rethought things from first principles every time you learned information that conflicted with how you currently thought the world worked, you would starve to death pretty quickly. Thus do creationists keep their beliefs despite geological dating, and thus do atheists keep their beliefs despite soft tissue in dinosaur bones. For any worldview, there are observations about the universe that have troubling implications, I think. It's my personal belief that the human mind is just too small and simple a thing to fully know and understand the universe, and that no human will ever be able to do it, so I don't worry about having a perfect philosophy. I try to figure out what seems to make the most sense based on what I've experienced to date, and go with that, even if it's not perfect.

    As far as Christians not investigating evolution - most people, regardless of their beliefs, refuse to examine other people's beliefs. It's a very common human trait - while I know very few creationists who've read Dawkins, I also know very few atheists who've actually read the Bible, and even fewer who've actually read any serious defenders of Christianity (C.S. Lewis is a decent place to start). It's pretty obvious to me that people are fundamentally selfish, greedy, angry jerks, who don't want to actually understand anyone else's perspective (I see this tendency in myself on a daily basis, which is why I believe it).

    As a theist who doesn't quite buy macroevolution, I've read chunks of Dawkins, and I don't find his arguments at all persuasive. Terry Eagleton wrote a scathing review [] of The God Delusion that summarizes the apparent gulf between Dawkins' arguments and what many theists believe pretty well. However, in case I've missed something, I'm planning to do a good careful read of some of Dawkins' books again this summer, to be certain I really do get what he's trying to say. I've had The God Delusion, The Blind Watchmaker, and The Ancestor's Tale recommended to me. Any other additi
  • by Anonymous Coward on Monday June 15, 2009 @08:35AM (#28333933)

    The presence of "print" ridges and valleys on the human hand extends to the entire gripping surface and, arguably, a small area just beyond. They clearly have a key role in gripping, touch or both, but I'm not sure how useful it is to show that they don't help much with friction on the sort of overly-smooth surface that rarely occurs naturally.

    For what it's worth, mind, my vote is for a "cat's whiskers" sort of sensory function - that having raised ridges increases skin distortion as objects are touched, which in turn increases sensitivity, precision and discrimination in the hand as an organ of touch.

In the realm of scientific observation, luck is granted only to those who are prepared. - Louis Pasteur