The notion of using fingerprints in the investigation of crimes and as a means of identifying individuals began in the late 1800s. Prior to this, many cultures had been aware of unique fingerprint properties, and even ancient societies used fingerprints in clay as a form of identification.
Babylonians were using fingerprints and clay tablets for business transactions. Obviously, it was not the sophisticated process that it is today, and people were not aware that fingerprints are so unique and that they stay with a person for their entire life, but they understood there was some significance.
Fingerprinting has been a staple of what we understand police work to be for many years now. Even if you’ve never had to deal with a criminal investigation, you probably have seen enough movies and TV shows to understand how the process works. The suspect leaves their fingerprints at the scene. The prints get dusted and lifted and compared to some database, and then someone is arrested based on fingerprint evidence. Since everyone has a unique fingerprint, you must have been at the crime scene if your fingerprint is there. Pretty simple stuff.
Have you ever wondered why fingerprints are unique? What purpose do they serve and why do they need to be so different from one person to the next? A lot is going on right at your fingertips and some of the explanations are pretty interesting.
What is the Purpose of Fingerprints?
At first glance or touch, it’s hard to appreciate what fingerprints do for you. If you rub your thumb and forefinger together right now, it probably feels fairly smooth. Even though you know your fingerprints are there, you’re not going to feel the texture of them. Ironically, however, the texture of your fingerprints is incredibly important to how you feel the world.
For a long time, one of the prevailing theories about why you have fingerprints was that they provide grip or traction. They were compared to the treads on tires and the idea was that, fine though they may be, they allow you to create friction and therefore grip so you could hold on to things.
In reality, when the theory was tested, it was shown that fingerprints, in fact, do the opposite. They reduce the friction between your fingers and the objects you’re trying to hold or touch. Fingerprints may improve your grip under wet conditions, but it’s actually harder to test that theory than you would think and there’s no definitive answer on it.
Some studies show that moisture can actually increase your grip. You have a lot of sweat glands in your fingers and when you grip a smooth surface, the sweat pores on your fingertips can ensure you are hydrated enough to get a good grip. Interestingly enough, the grooves in your fingerprints may also help grip something that is too wet by allowing dirt and moisture to follow the channels away, making it easier for you. You still might not be able to grip it, but you can grip better than you would without fingerprints.
The other theory that stood up better under testing was that fingerprints aid you in your sense of touch. Our fingers have several mechanoreceptors that respond to touch in them, but one kind, 2mm below your fingerprints, is called Pacinian corpuscles. When biomimetic sensors were tested, one smooth and one ridged like it had fingerprints, the fingerprinted version created vibrations at the exact frequency Pacinian corpuscles are sensitive to, thus indicating a finger with prints would be far more sensitive to fine textures than a finger without them. The vibrations were 100 times stronger.
If you didn’t have fingerprints, then everything you touched would be very similar to handling the world with rubber gloves on. Your ability to gather and interpret sensory data through your sense of touch is very dependent on your fingerprints. Being able to appreciate the subtleties of something soft, smooth, rough, leathery, silky, or anything like that is much harder if you don’t have fingerprints.
Are Fingerprints Really Unique?
All of us have heard that your fingerprints are unique multiple times throughout our lives. It’s just something we take for granted at this point. Like snowflakes, no two are unique. However, it’s worth taking a moment to consider what that implies. Has anyone ever fingerprinted you? What about your parents? Your best friend? If you take any 10 people, you’re probably going to find a few who have never been fingerprinted before. And if that’s true, then how do you know all of our fingerprints are different for sure?
It might be a little pedantic to ask that question, but the fact is saying all our fingerprints are unique is a generalization rather than a proven fact. We believe they are unique because, for all the ones we have recorded, they have been different. It makes sense to believe they are all unique, and for the most part, they appear to be that way. But you can’t definitively say that they all are because there is not enough data to back that statement up.
The idea stemmed from the adoption of fingerprints as a crime-solving method. It was seen as an immutable science. It didn’t need to rely on a witness who may have seen something in the dark and wasn’t sure. It didn’t have to rely on supposition. Prosecutors could bring the image of a fingerprint from a murder weapon into a courtroom and then the fingerprint taken off the suspect on trial and show them side by side. It didn’t have to rely on appealing to anyone’s feelings or preconceived notions. It was a pure science, at least that was how it was presented.
As pure science, fingerprinting had to be infallible. So that meant no two fingerprints could be alike, and the idea was just accepted as fact. It’s pretty much been that way for over a hundred years now. In fact, in 1894, it was published in Scientific American that the odds of two prints being identical were one in 64 trillion. That means it will be over one million years before someone who has your identical prints is likely to show up.
One of the reasons that DNA evidence is more heavily relied on today than fingerprints for solving crimes is because of the potential problems with fingerprints. For instance, do you know how to tell two fingerprints apart? If they’re incredibly different, sure. But what if two were remarkably similar? You’ve probably seen on crime shows when there are little areas that are circled on a fingerprint, these loops and whorls.
Fingerprint matching needs to line these up, but not every jurisdiction has the same standards. In some places, 12 characteristics need to match. In the UK it used to be 16 points and then, in 2001, they just changed it to whatever an expert concluded, as long as they could defend the conclusion. In the US, it can change from one county to another, with some not having any set standards. So the point matching, if they use it at all, could be 6, or 12, or 16, although 12 is sort of the go-to.
Given that some fingerprints are partials or smudged, it makes doing this job even harder and there has been some criticism of it as being infallible.
No two people have ever been recorded as having the same fingerprints before. Thus, it’s not unreasonable to say that all fingerprints are unique. Even identical twins have different fingerprints. But when there are not any particular standards for comparing fingerprints, it means that there’s potential for innocent people to be convicted and guilty people to go free because the science isn’t being pursued as purely as it should be.
One fairly recent advancement in fingerprint comparison and study has come thanks to AI analysis. In 2024, it was revealed that similarities between fingerprints could be detected between different fingers of the same person. This was something forensic science had never noticed before, but a computer was able to analyze different prints and determine with a success rate of up to 77% if two prints came from the same person, even though they might have come from different fingers.
This doesn’t mean that your fingerprints aren’t unique. It’s not like you’re sharing prints with a complete stranger, but it does mean they aren’t unique from one finger to the next, which is not something forensics realized before. Or at least not that unique.
Why Are They Different?
So there’s a reason for fingerprints, that’s all well and good. But what is the reason they’re so unique? Wouldn’t it be just as easy if they were all mostly the same? Not that your genes put a lot of effort into doing things, but it seems like maybe wasted effort if that’s the right term, for them to become so unique in each and every person.
As it happens, your fingerprints are a little bit feral. In the same way that zebras get stripes and a leopard gets spots, you get fingerprints. Researchers investigating how fingerprints form discovered that they begin before birth in the epithelium. Before they form into what they look like now, they resemble hair follicles. Several genes are activated, which operate uniquely compared to hair follicles, however, to develop prints on your fingers.
Once the genes are activated, they follow a Turing pattern. Turing’s idea was that natural patterns, like stripes and spots, might be due to a pair of molecules working together. One is an activator and one is an inhibitor. They always work in conjunction, sort of reigning each other in and allowing for these specific patterns to form and branch out, covering the whole organism or, in our case, our fingertips.
The active genes produce proteins that work as an activator, and other proteins work as an inhibitor, much like Turing suggested. The patterns begin in the three places across the fingers – near the nail, right in the middle, and then down near the crease in the first knuckle. The patterns spread out from those spots and end up merging and creating that unique fingerprint that you have that will be different from anyone else’s. How and where they start and spread will always be a little different from person to person, hence the uniqueness.
Do They Ever Change?
So your fingerprints are unique when they are formed, but do they stay that way? Over the course of a human’s life, your appearance will change dramatically. Everything about you will change, so do your fingerprints not go through an alteration of any kind?
Your fingerprints do change over time, just like the rest of you. That said, it’s not nearly enough to give you a get-out-of-jail-free card for committing crimes. Analysis of fingerprints that had been taken over five years showed that there is some variation, but it is basically statistically insignificant. And in terms of matching fingerprints from early to later, it’s a negligible difference that no computer would ever mess up.
Even after 12 years, the matches were still within the margin of error. Computers can notice a difference and you can definitely see that your fingerprints have changed, but it’s still not enough to hope that you can possibly get away with a crime if you’ve left fingerprint evidence behind.
The problem with matching fingerprints would only come with poor-quality prints to begin with. That is to say, it was a bad image or a partial print that wasn’t scanned very well. That, combined with age, could certainly make it difficult to match prints, but age is really not a factor.
A person can temporarily destroy their fingerprints by trying to cut them off or burn them with acid, or something. But your fingerprints will heal and when they grow back, they will be the same as they ever were. In short, you’re stuck with your uniqueness forever.