Why Do People Have Fingerprints?

There are billions of people on planet Earth, yet you’ll never find two people with the same set of fingerprints. Even identical twins have different fingerprints! Why is that?

Fingerprints can show a random pattern that no computer could replicate. Their development occurs because of genetics and the environment. Nearly all of the factors that go into each of our own fingerprints, however, are completely random.

Source:  www.publicdomainpictures.net Source: Darren Lewis

Fingerprints really help us out in nature, as well. A leading theory is that they most likely developed as a way for humans to grip objects better. After all, fingerprints are nothing more than narrow grooves and channels within the layers of the skin, almost like the tread found on running shoes.

Another postulates that fingerprints formed as a way for our skin layers to stretch out more, decreasing the chance for injury on one of our most sensitive and necessary areas of the body.

History of Fingerprints

Since then fingerprints have evolved to have other uses. Fingerprints can be found on ancient art dating all the way back to the ancient Babylonians and Egyptians. In Babylon they were even used to sign documents, telling us that people long ago knew of their unique aspects. The same took place in China during the third century BC.

It wasn’t until the 1820s, however, that a Czech physiologist named Jan Purkyne wrote and published a thesis that detailed nine unique fingerprint patterns. By 1858 fingerprinting in India had begun and in 1902 it gained international recognition with the Scheffer case in the United States, the first case to use fingerprints to prove that a murder occurred.

Since then fingerprints have become an accepted part of law enforcement, reliable identification, and even computer encryption. They’ve entered our cultural consciousness through books, films, and television and will only be used more in the future.

Types of Fingerprints

We all have fingerprints, that’s clear, but how do they form, and why?

The outer epidermis and the inner subcutaneous tissue both enclose the dermal cell layer between them. As the pressure builds, this layer compresses and buckles, erupting in random surface patterns. All of this occurs in the womb, the place where fingerprints are made.

But that doesn’t mean we can’t see some similarities in fingerprints. When fingerprint identification began there were three main systems used. One that gained the largest foothold in the English-speaking world was that of Edward Henry.

Henry noticed three main types of fingerprints: the arch, which makes up about 5% of fingerprints; the whorl, which makes up about 35%; and the loop, which makes up about 60% of all fingerprints.

Back in 1900 when Henry first published his findings that was a big deal. Since then systems have been developed that recognize even more fingerprint patters, such loops that are radial-shaped or ulnar-shaped, and arches that can be considered more-tented or simply plain. Whorls aren’t left out either, and you can classify them if they’re plain, accidental, composite, central-pocket, double-loop, and even peacock’s eye.

Fingers are classified as either R or L and each finger on the hand is also identified by an initial such as ‘m’ for middle finger or ‘p’ for pinky. When written out, each hand almost reads like a mathematical formula.

The Use of Fingerprints

We’ve already discussed a bit on how fingerprints may have been used for gripping or simply as a way to prevent injury. Scientists have of course studied fingerprints greatly, and here are some of their recent findings.

In 2009 scientists at Paris’ Ecole Normale Superieure found out that vibrations are integral in giving us a greater sense of touch. There were actually special nerve-endings called Pacinian corpuscles that were picking up these vibrations.

They also theorized that the swirl patters of fingerprints are coming about because that way a perpendicular angle is always in contact with a surface being touched. Those scientists also found out that those ridged-nerve endings were sending information back to the brain’s sensory neurons.

Where Fingerprints are Found

We know that police use fingerprints to solve crimes. We’ve all seen TV shows where police pull a print off of some surface, but what we might not know are what those surfaces always are.

There are four main types of fingerprints in this regard: exemplar, latent, patent, and plastic.

Exemplar prints are those taken from a subject or given willingly. Think of someone being brought into the police station and printed or someone getting some biometrics done at the hospital or a government office. These are the typical prints seen on ink blotter sheets.

Latent prints are those left on some surface, typically in another material. Think about movies where a murder occurs, and a fingerprint is left in blood. This can also occur with things like oil, dirt, and even the natural oils and sweats of our hands.

Patent prints make an indelible mark on the surface they touch. If you’ve ever pressed your finger into wet clay you’ve probably seen how the print and shape of your finger remains. This is an example of a patent fingerprint.

Plastic prints are very similar to patent prints in that they’re left in some other material. Think of leaving your print in wax or touching an especially dusty old car. Investigators can often lift these prints right off, not having to take pictures of them.

As you can see fingerprints have a long and varied history. They’ve always been known as being unique, although the reasons are still shrouded in mystery and still being researched. The use of fingerprinting to solve crimes is also a recent phenomenon, and one that’s gained traction all over the world.

Notes

Conklin, Barbara Gardner, Robert Gardner, and Dennis Shortelle. Encyclopedia of Forensic Science: a Compendium of Detective Fact and Fiction. Westport, Conn.: Oryx, 2002. Print.

Engert, Gerald J. (1964). “International Corner.” Identification News 14 (1).

Henry, Edward R., Sir (1900). “Classification and Uses of Finger Prints” London: George Rutledge & Sons, Ltd.

Further reading

Onin.com – The History of Fingerprints
HowStuffWorks – How Fingerprinting Works
Federal Bureau of Investigation – Fingerprint Identification Overview (PDF)