It is due to the process of tissue growth. Formation of these fingerprints can be caused by the surface buckling of the skin near the finger of the growing skin. There are many different types of fingerprints: Arch, tent-arch, loop, double loop, pocked loop, whorl and mixed, meaning that not two people have the same fingerprint, they would have different shapes and textures to it. The test of fingerprints in the scene of the crime, are done and verified in the forensic laboratory to see if the accused person were at the murder venue. They would check other fingerprints of other past offenders in the crime database to see if any of them tallies with the owner of the fingerprint at the crime scene.
Fingerprints are not an entirely genetic characteristic. Fingerprinting is an example of a phenotype. This means that it is determined by the interaction of an individual's genes and the way the baby develops in the uterus. The shape of fingerprints are influenced by environmental factors during pregnancy such as blood pressure, levels of nutrition and the overall position in the womb and the growth rate of the fingers at the end of the first trimester. (The first three months of the pregnancy) Thus, you will find similar patterns of ridges in the fingerprints of identical twins. The seven types of fingerprint are loop, accidental, double loop, central pocket loop, plain arch, plain whorl, plain arch, and tented arch. The use of fingerprinting allows police an extremely accurate means of identification. In earlier times branding, tattooing, or even maiming was used to mark and identify criminals. Although man had been aware of the fact that each person possessed a unique set of ridges on the fingers and hands, the use of these prints for criminal identification was not accepted until the early 1900s.
You could answer your own question somewhat if you asked yourself why are faces different. We are all human but we are all highly unique, excepting of course ,identical siblings but even they are exposed to environmental differences, which begins in utero. Though identical siblings have the same DNA, their fingerprints can differ, though they are similar.
There are several basic patterns of fingerprints, including whorls (spirals) and arches. Then within those basic types there is a lot of room for variation. As to why we have fingerprints - apes and monkeys have them too, so maybe it has something to do with grip, and the ability to use fine touch - needed for dexterity.
A possible explanation of the variety of fingerprints comes from the consideration of the mechanics of the tissue growth. Formation of fingerprints is a result of the surface buckling of the growing skin.
