Why is Every Fingerprint Unique?
First of all you need to know that fingerprints form during fetal development.
Genes determine differences in developmental timing that result in the three basic shapes: whorls, loops and arches. The small variations to these shapes, which make no two sets of fingerprints the same, are random and not inheritable.
At about week six in the womb, the tips of the fingers start to develop raised, swollen tissues, called volar pads.
These pads stop growing around week 10 and are absorbed when the rest of the finger tissue continues to grow. This physical process causes the skin to contract into the ridges and grooves that make up fingerprints.
Exactly when the contraction occurs determines the basic shape.
If the skin begins to fold into ridges while the volar pads are still prominent, the print is usually a whorl, which is a circular or spiral pattern.
If the folding happens after they’ve been absorbed a little more, the fingerprints are loops. But if the skin folds very late in the process, when the pads are almost gone, arches are formed instead.
Random differences in the patterns also emerge during the absorption, making even identical twins’fingerprints unique.
Fingerprints come in three basic shapes
Loops are the most common, occurring in about 65 percent of fingerprints. They form a hairpin pattern (here a double loop is shown).
Thirty percent of fingerprints are whorls – circular or spiral patterns. Arches, the least common shape (5 percent), rise up like tiny mountains.