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What is the difference between all fingerprints? And how are they different? I looked at my fingers and they are not different. How do we know if they are the same or different?
Question Date: 2017-09-15
Answer 1:

A fingerprint is the impression left as a result of the friction ridges (or raised portion of the skin consisting of multiple connected ridges) on a human finger (or other primates). Human fingerprints are detailed, nearly unique, difficult to alter, and persist over a whole human lifespan.

These ridges are caused by the underlying dermal papillae (small, nipple-like extensions of the uppermost layer of the dermis) into the epidermis. The ridge patterns are partly determined by genetics that develop before birth; even identical twins who share DNA will not have identical fingerprints. And they are partly developed from the pressure on a fetus's developing fingers in the womb.

The main purpose of the dermis is to support the epidermis. The ridges cause an increase in surface area between these two layers, thus strengthening their connection and helping prevent the layers from separating. These ridges also assist in helping the finger sense fine textures, and may assist in gripping wet surfaces.

The patterns of these ridges are commonly described as arches, single loop, double loop, and whorls. The flexibility of friction ridge skin means that no two finger prints are ever exactly alike in every detail. Even two prints from the same finger may be slightly different.

When fingerprints are used for identification, the prints are scored using a set of thresholds to determine the probability that the prints come from the same person. Modern day live scanning devices image your fingers and measure the physical differences between ridges and valleys. The uniqueness of fingerprints is determined by the arrangement, shape, size, and number of lines within the pattern. Scientists analyze very tiny characteristics, called minutiae, which cannot be seen with the naked eye.

Therefore, you may have looked at your fingers, but the prints will still have distinct characteristics.

Answer 2:

My fingerprints look the same, too - at least for the 4 fingers on my left hand.

Every person is supposed to have fingerprints that are different from the fingerprints of every other person. The patterns of the lines and curves are supposed to be different for every person.

Here's what Wikipedia says about this:

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