Reading the fine print

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Health / Medicine / Myths

I remember being told in primary school no one else on the planet had exactly the same fingerprints as me. Pretty powerful stuff for a seven-year old. It was thrilling to press my fingers onto the ink pad and look at the patterns my fingerprints made on paper. Patterns that were uniquely mine and that I’d never really looked at before, despite the fact they had been part of me since before I was born. But is it true? Are each of your fingerprints truly one of a kind?

Fingerprints. Source: iStock

Your fingerprints are formed in the womb, so even identical twins have different sets of prints. Image source: iStock

‘There is no one alive who is Youer than you’

It seems Dr Seuss got it right back in 1959, at least when it comes to fingerprints. In fact as far as we know no two people who have ever lived share an identical set of fingerprints.

Fingerprints, otherwise known as Friction Ridge Skin (FRS), come in three basic patterns: loop, arch and whorl. These describe the overall shape of the tiny ridges you see if you look closely at your fingertips. It’s possible to have just one, or two, or all three patterns of fingerprint across your ten fingers. We’ve known for many decades the overall pattern of your fingerprints is inherited, but there are a number of genes involved so it’s not as simple as saying you’ll definitely have identical patterns to one or both of your parents.

And although your genes play a big role in your fingerprint patterns, that’s not the full story. The exact path of the ridges, as well as the breaks and forks in the ridges, are affected by the conditions you were exposed to before you were born. Your fingerprints are formed during a fascinating process which began about ten weeks after you were conceived. Because these ridge features aren’t a result of genes, even identical twins end up with different fingerprints. Perhaps one twin had a slightly longer umbilical cord than the other, or simply experienced more pressure from the walls of the uterus. There are a variety of factors that can affect the environment a fetus is exposed to, which in turns affects fingerprint formation.

What use are fingerprints anyway?

It’s not just humans who have fingerprints: other primates have them too. It has long been assumed primates evolved fingerprints to provide added friction, which is obviously very useful for handling objects or climbing trees. More evidence for the friction argument comes from the fact animals like koalas, which also move through trees, have fingerprints not terribly different to ours. Great theory.

The only problem is that when scientists tested the friction created by fingerprints, they found the ridges didn’t assist with gripping at all. Others have suggested the ridges on our fingers may assist with drainage and improve grip in wet conditions or may simply improve our sense of touch.

Exactly why we evolved fingerprints is still up for debate, but we do know humans can do fine without them. A handful of people in just five Swiss families have a genetic mutation resulting in them being born without fingerprints. These fingerprint-less people are fine except when trying to cross a border, explaining why this condition has also been dubbed the immigration-delay disease.

At the scene of the crime

As a result of their uniqueness, fingerprints have long been considered a foolproof method of identification. Fingerprints were first used to convict a criminal in Argentina in 1893 and continue to be used as evidence in a high proportion of criminal cases. These days it’s routine to use your fingerprint to unlock your smartphone, a feat achieved simply by authenticating your prints against a stored template.

These uses also assume our fingerprints are fixed, but recent studies have shown in fact our fingerprints change over time. Of course permanent damage like scarring can change a fingerprint but we now know there are other more subtle changes that happen over time.

More drastically, we recently heard the case of a Singaporean man who lost his fingerprints as a result of cancer treatment. It turns out bricklayers also wear down the ridges on their fingers because they spend so much time handling heavy, rough objects.

What your prints say about you

Despite persistent claims your fingerprints reveal your personality, and can be used to predict your ideal job and your destiny, there is no evidence for any of these things. What a shame! Just last week it was announced three-thousand-year-old fingerprints have been found on the lid of an Egyptian coffin. Imagine if those prints could tell us something of the life of the craftsmen they belonged to.

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    • Hi Garry! I think it depends on both the machine being used and particularly on the quality of the fingerprints. But my understanding is that with good prints, the risk of misidentification is tiny.

  1. I love how scientists find all sorts of wonderful things to understand. The finger grip experiment is delightful. I must admit, that measurements such as co-efficent of friction don’t readily come to mind when I think of the humble fingerpad.

  2. Pingback: What do your fingers say about you? – Espresso Science

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