Why Do We Have Fingerprints?

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Everything You Need to Know About Fingerprints

Fingerprints on a Scanner
Fingerprints are ridged patterns that form on our fingertips. We all have unique, individual fingerprints for life. Paper Boat Creative/Digital Vision/Getty Images

For over 100 years scientists have believed that the purpose of our fingerprints is to improve our ability to grip objects. Researchers have discovered that fingerprints do not improve grip by increasing friction between the skin on our fingers and an object. In fact, fingerprints actually reduce friction and our ability to grasp smooth objects.

While testing the hypothesis of fingerprint friction, University of Manchester researchers discovered that skin behaves more like rubber than a normal solid. In fact, our fingerprints reduce our ability to grasp objects because they reduce our skin's contact area with the objects we hold. So the question remains, why do we have fingerprints? No one knows for sure. Several theories have arisen suggesting that fingerprints may help us to grasp rough or wet surfaces, protect our fingers from damage, and increase touch sensitivity.

How Fingerprints Develop

Fingerprints are ridged patterns that form on our fingertips. They develop while we are in our mother's womb and are formed completely by the seventh month. We all have unique, individual fingerprints for life. Several factors influence fingerprint formation. Our genes influence the patterns of ridges on our fingers, palms, toes, and feet. These patterns are unique even among identical twins. While twins have identical DNA, they still have unique fingerprints. This is because a host of other factors, in addition to genetic makeup, influence fingerprint formation. The location of the fetus in the womb, the flow of amniotic fluid, and the length of the umbilical cord are all factors that play a role in shaping individual fingerprints.

Fingerprints consist of patterns of arches, loops, and whorls. These patterns are formed in the innermost layer of the epidermis known as the basal cell layer. The basal cell layer is located between the outermost layer of skin (epidermis) and the thick layer of skin that lies beneath and supports the epidermis known as the dermis. Basal cells constantly divide to produce new skin cells, which are pushed upward to the layers above. The new cells replace older cells that die and are shed. The basal cell layer in a fetus grows faster than the outer epidermis and dermis layers. This growth causes the basal cell layer to fold, forming a variety of patterns. Because fingerprint patterns are formed in the basal layer, damage to the surface layer will not alter fingerprints.

Why Some People Don't Have Fingerprints

Did you know that some people are born without fingerprints? Dermatoglyphia, from the Greek derma for skin and glyph for carving, are the ridges that appear on the fingertips, palms, toes, and soles of our feet. The absence of fingerprints is caused by a rare genetic condition known as adermatoglyphia. Researchers have discovered a mutation in the gene SMARCAD1 that may be the cause for the development of this condition. The discovery was made while studying a Swiss family with members that exhibited adermatoglyphia.

According to Dr. Eli Sprecher from Tel Aviv Sourasky Medical Center in Israel, "We know that fingerprints are fully formed by 24 weeks after fertilization and do not undergo any modification throughout life. However, the factors underlying the formation and pattern of fingerprints during embryonic development are largely unknown." This study has shed some light on fingerprint development as it points to a specific gene that is involved in the regulation of fingerprint development. Evidence from the study also suggests that this particular gene may also be involved in the development of sweat glands.

Fingerprints and Bacteria

Researchers from the University of Colorado at Boulder have shown that bacteria found on the skin can be used as personal identifiers. This is possible because bacteria that live on your skin and reside on your hands are unique, even among identical twins. These bacteria are left behind on the items we touch. By genetically sequencing bacterial DNA, specific bacteria found on surfaces can be matched to the hands of the person from which they came. These bacteria can be used as a type of fingerprint because of their uniqueness and their ability to remain unchanged for several weeks. Bacterial analysis could be a useful tool in forensic identification when human DNA or clear fingerprints can not be obtained.

Sources:

  • Journal of Experimental Biology. "Urban Myth Disproved: Fingerprints Do Not Improve Grip Friction." ScienceDaily. ScienceDaily, 15 June 2009. (www.sciencedaily.com/releases/2009/06/090612092729.htm).
  • University of Colorado at Boulder. "New hand bacteria study holds promise for forensics identification." ScienceDaily. ScienceDaily, 16 March 2010. (www.sciencedaily.com/releases/2010/03/100315161718.htm).
  • Cell Press. "Mutation linked with the absence of fingerprints." ScienceDaily. ScienceDaily, 8 August 2011. (www.sciencedaily.com/releases/2011/08/110804123904.htm).
  • Britt, Robert. "Lasting Impression: How Fingerprints Are Created." Live Science. 2 November 2004. (http://www.livescience.com/30-lasting-impression-fingerprints-created.html).