Science

VIDEO. Camille’s chronicle: what are fingerprints for?

CJAMY. Camille Gaubert’s column is broadcast daily in the program “C Jamy”, presented by Jamy Gourmaud from Monday to Friday at 5 pm on France 5.

Our fingerprints are unique, even between identical twins. They form in the first months of pregnancy and do not change. Their usefulness is still being studied, but it seems that they help us have a better sense of touch!

Fingerprints take shape in the first half of pregnancy

To understand, you have to go back to the beginning. It is during the first five months of pregnancy that dermatoglyphs, that is to say the patterns on the tips of our fingers that leave fingerprints, develop. At first, the fetus has smooth fingers. But over the weeks, the top two layers of the skin, the dermis and the epidermis, grow larger and put pressure on each other. They fold, like a kind of puff pastry. In the middle of the pregnancy, the reasons are definitively fixed. This process is partly guided by genetics, but also by external factors, such as the position of the baby in the womb. This explains why even identical twins have different fingerprints.

One in 100,000 billion chance of finding two identical fingerprints

Result: Scientists estimate the probability that there are two identical to 10 to the power of -14, or 1 chance in 100,000 billion. The forensic science also considers that this is impossible. To compare two fingerprints, the forensic science compares their particularities: ridges, bifurcations or line breaks. We call this minutiae. When they find 12 identical minutiae between two prints, and no discrepancy, the forensic scientists conclude that it is the same person.

Better sense of touch

But what are these dermatoglyphs for, after all … Apart from finding the criminals? According to scientists, dermatoglyphs amplify vibrations when we pass our hand over a surface, and therefore better perceive textures. Suddenly, that would give us a finer sensitivity allowing us to better handle objects, especially wet ones. In 2021, researchers showed that each sensory neuron in our fingers was linked to one of the ridges of our fingerprints, and that they had a detection area as fine as said ridges: 0.4 mm. These detection zones overlap strongly: thus, when an object is touched, the group of neurons stimulated varies according to slight modifications of the stimulus, giving us a significant sensitivity to texture, pressure or even vibration.

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