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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.
    • Yup. (Score:3, Insightful)

      by El Jynx ( 548908 )

      Sounds about right. Such micro-ridges, I think, WOULD increase grip on rougher surfaces, which is what we would run into in daily life. Also, if those ridges - generally the top layer of skin - would rip off or shred, the damage done to the hand would be less than were it smooth, I would guess. IOW, maybe a safety feature?

    • Re: (Score:3, Insightful)

      by Anonymous Coward

      There are probably multiple reasons for the fingerprints.

      The skin has to be both flexible and durable at the same time, and gripping on moist surfaces should also be safe.

      A flexible skin is also allowing for better dexterity and a finer resolution when sensing surfaces.

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

      I would guess that the only question is why at all do we have finger prints. The uniqueness would then be expected since it would be much more complicated for a system giving rise to same print for everyone to evolve. Start with a system that produces finger prints (for whatever reason), and the usual error while copying the genetic code would certainly make sure that people get unique finger prints.

      • Or maybe the command is simply 'make tiny ridges' and leaves the body to figure out the details.
      • Re: (Score:3, Informative)

        by osu-neko ( 2604 )
        Even without errors in copying the genetic code, people get unique finger prints. The overall pattern and general style will end up the same, but they're still unique, even between twins with identical DNA. Reminds me of the markings on the cloned cat. The clone was a calico, just like the original, but that seemly random pattern in a calico's fur? Turns out, it actually is somewhat random. Identical DNA doesn't produce identical fingerprints either...
    • Re: (Score:3, Interesting)

      by Threni ( 635302 )

      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: (Score:3, Funny)

        Fingerprints would probably evolve away within a few generations if people didn't need the increased friction on the iPod click wheel.
    • 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.

      • Re: (Score:3, Insightful)

        Most mutations that get kept are somehow beneficial. Not all, but most.

        • Re:Primates (Score:5, Insightful)

          by stonewallred ( 1465497 ) on Sunday June 14, 2009 @11:18AM (#28326643)
          most evolutionary features get kept that do not kill the person/animal having it, and which does not put it at a disadvantage in reproducing. There are many more evolved features that do nothing that have been kept than you think.
        • Re:Primates (Score:4, Informative)

          by linguizic ( 806996 ) on Sunday June 14, 2009 @01:17PM (#28327393)
          It depends on what scale you're looking at [wikipedia.org]. Neutral Theory says that MOST mutations are neither beneficial nor harmful.
      • Re: (Score:2, Insightful)

        by bluesatin ( 1350681 )
        Well the main route for evolution to occur (survival of the fittest) is pretty much dead.
      • for right now, some people are the pinnacle of human evolution, until human evolution evolves and leaves those without wisdom teeth in the dust.

        You can look at individual mutations as alpha builds, communities with the same mutation as unstable beta builds, and traits shared by the entire (well, to like 5 nines) population as stable release. Simply because there will be a future build of debian doesn't mean I can't use lenny stable to satisfaction.
      • Re:Primates (Score:5, Insightful)

        by Reziac ( 43301 ) * on Sunday June 14, 2009 @12:02PM (#28326881) Homepage Journal

        Exactly -- why does it have to be for any particular use? More likely it's just an artifact of how skin develops. People forget that many traits didn't evolve for a specific purpose, but rather, were random mutations that were not selected against, becauee they did the species no harm.

        The whole question also shows a profound ignorance of the rest of the animal kingdom:

        Dogs have noseprints that are as unique as fingerprints (and in fact are legal ID for dogs in Canada). Why is this? Probably no reason at all, other than quirks of individual cell layout in the skin layer.

        Chickens have similar uniqueness in the surface of their combs. Why? Likewise, probably no reason, other than it's just a trivial quirk of how the skin cells piled up in a given individual.

    • Re: (Score:3, Interesting)

      by 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 (Score:5, Funny)

      by houghi ( 78078 ) on Sunday June 14, 2009 @10:21AM (#28326403)

      We didn't evolve to grip glass.

      Yes we did. The better you can hold your glass, the more alcohol you are able to drink. The more alcohol you drink, the more likely you are to end up with some ugly girl who also was able to drink herself unconscious.

      Now imagine that you would drop your glass before you are at that point. You would never be drunk enough to go with THAT girl and she won't go home with YOU.

      Without fingerprints, we would be extinct by now.

      • Re: (Score:3, Funny)

        by Provocateur ( 133110 )

        And all this time I thought the fingerprints evolved for gripping the modern day equivalent of tree branches: subway straps and bus door handles.

    • Re: (Score:2, Insightful)

      by Hal_Porter ( 817932 )

      I don't see why them being unique is so surprising. Faces are unique after all. All of us have a unique genome, apart from identical twins. Still even twins have different fingerprints and hair follicles and so on are in different places. I guess when embryos develop the process for skin folding and hair follicle development is slightly random - i.e. the genes encode the probability of a fair follicle, not its exact location.

    • Re: (Score:3, Insightful)

      by amicusNYCL ( 1538833 )

      Thank you, I'm glad this is the first post listed.

      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.

      That's totally BS science. That disproves the hypothesis that fingerprints provide improved grip on acrylic glass, not that fingerprints provide improved grip on other surfaces.

    • Re: (Score:3, Insightful)

      by Lord Ender ( 156273 )

      Why presume they have a function? Evolution weeds out costly features. If fingerprints have little cost, it is wrong to assume they necessarily exist to serve some specific purpose.

    • 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.

  • by Anonymous Coward on Sunday June 14, 2009 @08:22AM (#28325869)

    It's obvious fingerprints were designed by our creator to help the Police catch murderers.

  • by gblackwo ( 1087063 ) on Sunday June 14, 2009 @08:22AM (#28325871) Homepage
    I also love how they never counterweight their centrifuges.
  • by Karganeth ( 1017580 ) on Sunday June 14, 2009 @08:26AM (#28325881)
    If it takes an equal amount of resources for the body to grow a finger without fingerprints then it makes sense that they not meant for anything. Not everything has to have a purpose.
    • Unlikely. (Score:3, Insightful)

      by El Jynx ( 548908 )

      It's more likely for something used this much to have functional features than not. Fingers and claws have been around for quite a while. It's hard to imagine them not evolving useful properties. Of course, this can go too far. Try peeling a gecko from a wall, you need to call the Hulk to help.

      • Do you mean Gecko, or "Gecko". One is the cute little guy that eats bugs and provides an easy thing to rescue girls from, the other is a 5 foot meat eating monitor lizard that tends to try and eat people trying to rescue girls from them.

    • Re: (Score:2, Insightful)

      by koolfy ( 1213316 )
      If fingerprints had no value (to survive/reproduce) in any way, species with and without fingerprints would be equal in the natural selection.
      That would imply that when a monkey would be born without those (genetic mutation somewhere), there would be no reason for him to be less likely to survive and reproduce than his peers having fingerprints, and when he would procreate, it would create a variation of those monkeys having no fingerprints.

      If we have fingerprints, it's genetically possible to be born
      • by maxume ( 22995 ) on Sunday June 14, 2009 @09:50AM (#28326221)

        Or a population of primates that happened to have fingerprints became dominant for some other reason.

        It is often the case that an environmental shift makes an existing trait advantageous (that trait may have been meaningless in the previous environment), rather than an advantageous trait arising in a static environment.

      • by funkatron ( 912521 ) on Sunday June 14, 2009 @09:53AM (#28326243)

        If we have fingerprints, it's genetically possible to be born without, so it's very likely that that mutation existed in the history of evolution, and that one of those specimen procreated, creating that fingerprint-less type of monkey/man.

        I would actually question to what extent this is a possibility. Human skin has all sorts of textures and patterns, most of which we don't treat with any significance. It may be that smooth skin is actually difficult to produce by biological processes. This is a possibility that should at least be considered.

    • Re: (Score:3, Funny)

      Not everything has to have a purpose.

      Sometimes parents can be mean.

  • They're for US immigration to scan. Other than that they serve no other purpose, like wasps.

    Seriously though, did you know that identical twins have different fingerprints? Not so identical after all.

    • Twins are very frequently very similar (same Mom same Dad same err "dice roll")
      "Identical" twins (the bet was "split") have some very minor things different due to those features having a nongenetic component (chaos theory get in the way)

      I would bet that direct clones of a person would also have Biometric differences.

    • Which may seem to imply that fingerprints are formed during development and are not determined by genetics.

    • by Bob9113 ( 14996 ) on Sunday June 14, 2009 @11:45AM (#28326785) Homepage

      Other than that they serve no other purpose, like wasps.

      Hey, if it weren't for WASPs, who would shop at The Gap or Banana Republic? Who would buy purse-sized dogs? And who would keep psychotherapists and badminton set manufacturers in business?

  • by itsdapead ( 734413 ) on Sunday June 14, 2009 @08:43AM (#28325941)


    I'll get my coat.

    • Re: (Score:3, Funny)

      by Anonymous Coward

      Make sure you have more than just the coat, okay?

  • tactile sensation (Score:5, Informative)

    by Anonymous Coward on Sunday June 14, 2009 @08:44AM (#28325949)

    There is a fair amount of evidence that they increase tactile sensitivity. We have nerves that are sensitive to specific vibrational frequencies. As fingerprints run over edges, then generate vibrations at frequencies we have maximal sensitivity for.


  • Maybe they work like treads on car tires... let there be someplace for liquids to move *away* from to improve grip. Or, maybe having "with oil" and "without oil" surfaces that can be selected by varying grip allows gripping different types of surfaces.

    Also, grip isn't the only thing hands do. Wiping or scrubbing with your fingers requires some level of abrasiveness.

    I suspect that there may be a connection between building calluses and having prints. Possibly, prints are just the way we make "tough" skin tha

  • 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: (Score:3, Informative)

      by amicusNYCL ( 1538833 )

      <quote>quote goes here</quote>

      If you copy and paste that you'll get this:

      quote goes here

      You can also do <b>bold</b>, <i>italic</i>, and a few other basic things:

      You can also do bold, italic, and a few other basic things.

  • by Anonymous Coward on Sunday June 14, 2009 @09:12AM (#28326055)

    The USA's National Public Radio show, "Science Friday" discussed this:


    The show talks about this result, and reveals that New world monkeys have similarly ridged
    skin on the gripping side of their tails. Touch sensitivity, and resistance to blistering are
    posited as potential answers.

  • Many things (Score:5, Insightful)

    by bytesex ( 112972 ) on Sunday June 14, 2009 @09:13AM (#28326063) Homepage

    More grip, larger surface, which means more flexibility, more nerve-endings - more sensitivity, better warmth-exchange, 'folded-up-ness', which means more protection from wounds, easier to clean (like footprints, the mud just falls out), 'little bits that stick out' - meaning more sensitivity again.

    • Actually it's the bits that don't stick out that provide the sensitivity. It's kind of like a microserrated knife, they're shaped like so if you turn them edge-up: ___A____A____A____A___ The edges of the A's and the flats are sharpened, and the A's sticking out protect the other sharp parts. The raised parts of your fingers are worn off quickly and easily (it's happened to me dozens of times... but I never burned them off, so they still come back every time, even when I get cuts etc) but the grooves aren't

  • by YourExperiment ( 1081089 ) on Sunday June 14, 2009 @09:15AM (#28326075)

    With articles such as this, it's hard to tell whether we're being subjected to bad science or bad journalism. Both the summary and TFA quite categorically state that the "myth" of fingerprints being used to improve grip has been disproven. They then go on to describe how this experiment tested whether fingerprints helped when grasping an extremely smooth surface, and found out that they didn't (well okay, actually they did, but not by very much).

    Finally, some alternate hypotheses as to why fingerprints evolved are posited, the first of which is: they may improve grip on rough surfaces. Not acrylic glass or anything, but those other kind of surfaces - you know, the type that actually occur in nature.

    I'm pretty sure I don't know much more now than I did before I read the article.

    • Bingo! Wonderful insight! The popular press (and /.) is a wonderful pool for fishing interesting topics for further reading, attention, or contemplation. Anyone I know who has lived life for any length of time and has experienced real world events only to have later read of them finds that almost all contemporary press accounts are either incomplete, misleading, or overly simplistic. That's not to indict the press. It's human nature. In the military one learns never to trust first reports. Criminologists sa
    • Hmm, so TFA says that the myth of fingerprints improving grip is busted, and then begin to posit that fingerprints improve grip? I call bad journalism, probably because the paper states other things to test, doesn't mention the myth, and the journalist wanted to go with the science busting myth meme that has been so popular since mythbusters premiered.
    • by Reziac ( 43301 ) *

      They may have more value in gripping *rough* surfaces, for the same reason that serrated knives stay sharp longer than smooth-edged knives -- only a small amount of the skin (or knife edge) ever comes in contact with abrasive hard surfaces, therefore improving skin (and knife) endurance. Also, it's easier to grip rough surfaces (as occur in nature) if the gripper isn't entirely smooth.

      But even after all that.. it's still extremely trivial as it would affect everyday life; I'd guess well below any threshold

  • by Hurricane78 ( 562437 ) <deleted@slashdot ... minus physicist> on Sunday June 14, 2009 @09:17AM (#28326079)

    Why do they have to be for something?
    Evolution does not forbid random things, that are neither bad nor good for something.

    Sometimes, humans try too much, to fit things into the artificial set of meta-rules that they did create, to describe the complex results of more basic and emergent rules. But those meta-rules have their own artifacts, that are not present in the basic rules and therefore are not present in the world. Like there having to be a "reason" for everything. A human concept that should describe causality, but adds something more to it, which does not exist in reality.

    Other than that, it is obvious, that they enhance the grip, even in situations with liquids.

  • So what? Who is to say they aren't slowly evolving away and they were much more pronounced in the past when we needed it living out in the wild?

    Much like an appendix, its most likely something once useful that is on the way out. Evolution doesn't happen overnight.

    • Re: (Score:3, Interesting)

      by Nirvelli ( 851945 )
      But the appendix isn't on its way out, it's there for after you've had diarrhea. [wikipedia.org]
      • by nurb432 ( 527695 )

        Such a function is expected to be useful in a culture lacking modern sanitation and healthcare practice, where diarrhea may be prevalent.

        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.

        • Re: (Score:3, Interesting)

          by johnsonav ( 1098915 )

          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.

  • my guess (Score:2, Interesting)

    by purpleque ( 948533 )
    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.
  • Celestial barcodes. The gods are thinking of moving towards an RFID based solution but for now it works.
  • 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.
  • I lose my fingerprints from time to time due to a skin condition, and I drop things a lot more when they're not there. While that's anecdotal and lacks a lot of scientific rigor, I'm not inclined to discard the idea that they're there to improve grip.
  • Fingerprints are for nothing. Fingerprints are a byproduct of the processes necessary for the production of new cell growth.
    • Nope.
      The fact that fingerprints are unique, and grow exactly in the same form even after a burn or erasure clearly shows a higher purpose.
      Don't you visit the Creationist mueseum in Texas.
      God made us. In his image.
      And his fingerprint is what all of us have.

    • by Reziac ( 43301 ) *

      That's my contention too... based on a lot of side-thoughts but mainly on the fact that dogs' noses also have a unique print, which probably serves no "purpose" either, but is just an artifact of the way skin develops, and the type of skin found on commonly-used pressure points (hands, feet, or with dogs, noses).

      Remember, your toes, soles, and palms ALSO have unique "prints". I'd hazard that the microwrinkles in everyone's skin are the same thing (and equally unique), just less "codified" because that skin

  • Obvious! (Score:3, Funny)

    by AmigaMMC ( 1103025 ) on Sunday June 14, 2009 @05:30PM (#28329413)
    Since we were genetically engineered by an extraterrestrial civilization they designed fingerprints in our DNA so that they could catalog us for later use.
  • by Douglas Goodall ( 992917 ) on Monday June 15, 2009 @08:45AM (#28333993) Homepage
    When you hold your hands together and pray, the fingerprints sign the prayer so God knows who it came from. That is why you hold your hands in front of your face in the usual pose. The prayer passes over both hands on it's way to God.

If I had only known, I would have been a locksmith. -- Albert Einstein