A Moment of Science

What Good Are Fingerprints?

Readers of detective fiction knows one thing fingerprints are good for, their unique patterns. Why have we evolved such convoluted fingertips and why so useful?

A fake example of a fingerprint

Photo: piddaz (Flickr)

A fake example of a fingerprint.

Any reader of detective fiction knows one thing fingerprints are good for, their unique patterns. They never fail to give away who done it.

For an evolutionary biologist however, the question is somewhat different. Why have we evolved such convoluted finger tips? What makes them useful?

For one, our fingerprints help us grip and hold onto things under a variety of conditions. If your finger tips were completely smooth, you would be able to pick up dry objects pretty well, but wet objects would literally slip through your fingers.

Finger prints form miniature channels for moisture to gather in. The ridges stick through the moisture, allowing a better grip. In this way, your fingerprint’s ridges work just like the all-season tires on your car. They increase your traction in all sorts of weather.

Fingerprints also help prevent blisters on the tips of your fingers.

Your skin has two main layers, the outer epidermis and the inner dermis. You get a blister when there is shearing, or sideways stress, which separates these layers. For example, if your shoe rubs the skin of your ankle too roughly, it can break the connection between the dermis and epidermis in that area. The space between the now separated skin layers fills with fluid, and you have a blister.

When the layers of skin are flat, sitting next to each other like books on a shelf, this kind of sliding can happen pretty easily. In a fingerprint, however, those ridges and channels form an interlocking geometry, like a waffle in a waffle iron. This helps hold the layers in place, preventing blisters.

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