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How and why do we have fingerprints?

Have you ever used a device that incorporates touch ID? If you have, you’ve experienced the modern-age use of fingerprint recognition. With everyone’s fingerprints being different, detecting someone’s fingerprint is a great way of uncovering someone’s identity. However, have you ever wondered how it is even possible for everyone in the world to have a different set of fingerprints, even twins who share the same DNA? Moreover, have you ever wondered what other potential (biological) advantages there are in having fingerprints? Surely we haven’t inherited fingerprints for the sole reason to differentiate individuals for the favour of society - evolution doesn’t work like that. In this article, I will be introducing the answers to these questions so that you understand the concept of how and why we have fingerprints.

 

What are fingerprints and how are they formed?

Fingerprints, which are scientifically known as dermatoglyphs, are folds/ridges of the outer layer of the skin called the epidermis.

 

figure 2 Skin Diagram

Fingerprint formation occurs during pregnancy. At around the 10th week, the basal layer of the skin grows faster than the other layers of the skin (epidermis and dermis), causing foldings to form. These foldings are what results in the surface layer of the skin to be folded as well and form what is known as ridges. The fingerprint is set when the fetus is 17 weeks old by this process (Leupen, 2020). Due to the basal layer being the layer that folds, even if we attempt to burn our fingerprints off (as some people did out of curiosity), they will regenerate!

Types of fingerprints

Have a look at your own fingers to see what type of fingerprint you have

The main 3 types of fingerprints are the arch, loop and whorl. The subcategories and images are shown below. 

 

Figure 3: types of fingerprints

Loop:

Loop fingerprints are the most common type of fingerprint, and they make up 60-70% of all prints. In total, there are 3 separate subcategories of loop fingerprints. Radial, ulnar and central pocket loops.

Whorl:

Whorl fingerprints make up 30% of all prints. There are also 3 subcategories of whorl fingerprints. Plain, double loop and accidental whorl fingerprints.

Arch:

Arch fingerprints are the rarest fingerprint, making up only 10% of all fingerprints There are 2 separate subcategories. plain and tented arch (Smart Eye Technology, 2022)

What determines the type of fingerprints we have?

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Genetics

Although it seems that the type of fingerprint we have may be derived from a gene relating to the skin, it was found that it was the gene responsible for finger length was in fact the determinant for our fingerprint type. This was found during the following experiment:

In order to find the balance of genes that may alter the probability of having an arch, loop or whorl fingerprint, scientists decided to assess the DNA from a group of volunteers. From there, they discovered that the genes responsible were mainly to do with limb and finger formation. Therefore, the gene EVI1 (a gene that develops the human limbs) was reduced in mice to see if it would have any effect on the ridges of a mice’s digits. The experiment showed a change, and therefore it was concluded that EVI1 was responsible for the fingerprint pattern (Young, 2022). Additionally, to further support this gene in being responsible for the type of fingerprints we have, scientists found that “fingerprint patterns were genetically correlated with hand proportions.” (Li et al, 2022)

Environment of the womb

Apart from genes, many other factors affect the formation of fingerprints. This is why even identical twins, who have the same DNA as each other, have different fingerprints from each other. These factors include: umbilical cord length, blood flow and pressure, position of fetus in the womb, rate of finger growth, access to nutrition in the womb (Cherney, 2019).

 

The fingerprint’s role in touch

Our fingers are known to have 2 types of neurons: type 1 (FA-1) and type 1 (SA-1). However, it was never found out how they mapped on the receptive field of fingertips. To find this out, Ewa Jarocka and her team brought 12 volunteers who, whilst sitting in a dentist’s chair, had their fingertips stimulated with a polymer ring. The electric signals that were picked up when the volunteers’ fingers were stimulated revealed that the receptive fields weren’t uniform and didn’t have a maximum sensitive point as suspected. Instead it showed that our fingers had “hotspots”, which are high sensitive points. These hotspots turned out to be mapped onto papillary ridges. Therefore, with the conduction of this experiment, it could be concluded that fingerprints help to enhance our sense of touch by acting as our finger’s sensitive spots (Mackenzie, 2021).

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The fingerprint’s role in grip: still unsure

Even though this role hasn’t been 100% confirmed to be real or fake, I still wanted to include this experiment since it disproved a theory which scientists had believed to be true.

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A famous theory that fingerprints helped with gripping smooth objects was debunked by Ronald Ennos, a biomechanics researcher. He thought that fingerprints worked like car tires to help increase friction; the grooves in tires help to increase surface area for friction. However, by dragging an acrylic plate across a person’s finger pad with varying force and finding how much of the finger was touching the plate, he found out that fingerprints actually reduced the surface area, and therefore friction, due to the fact that the valleys did not touch the plate. In other words, a finger with no fingerprints would provide more friction than one with fingerprints.

Figure 4 experiment 

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However, it still is not 100% proven that fingerprints are not used for grip. Scientists are now speculating that fingerprints help with grip underwater, but this theory is harder to investigate than the first theory (Bryce, 2019).

Ari Kim 13W, a student at Bangkok Patana School

Work cited:

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