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Why do we have fingerprints or 'prints' on only our palms and feet? Is there a difference between the types of the skin?
Question Date: 2011-10-28
Answer 1:

Good observation! The skin on our hands and feet is different. First, we dont have any hair there. Even places on your body that dont seem to have hair usually have short, fine hair. But the soles and palms have none. There are a lot of sweat glands here too.

For another thing, theres less pigment (color). Even people with very dark skin elsewhere usually have pinkish-white palms of their hands and soles of their feet.

The skin is also thicker (about 8-14 times thicker) here, which makes sense since theres so much chance to wear down these areas. The cells here divide sooner, while they are still smaller than skin cells in other places. The differences in color and thickness are because of one gene that makes a protein called DKK1. The body only makes this protein on the palms and soles.

Fingerprints (and footprints) are tiny ridges in the surface part of the skin (epidermis) that are formed by lines in the deep skin (dermis). They probably give us better grip by giving our skin more friction. They may also help keep the skin from tearing easily.

Scientists still havent figured out why the patterns are so different, but it probably has to do with ridges that form when the skin is first formed, only about 2 months after an egg is fertilized. As the growing layers push and pull, permanent ridges are made. We are born with the same fingerprints that we will have all of our lives.

Do you think identical twins have identical fingerprints?

Thanks for asking,

Answer 2:

The leading theory as to why we have fingerprints is that it enhances our sense of touch. The ridges are thought to pick up vibrations as we run our fingers (or toes) over a surface, giving our brains more physical input about whatever it is that we are touching. It makes sense, then, that we have evolved to only have fingerprints on our palms and bottom of our feet, since that is what we use by and large to explore our physical environment. This is also why we have a much higher level of sensory molecules and nerves in our hands and feet than in other places in our skin. You can test this by taking something with a really fine point, like a pen or a needle, and gently touching your fingertip and then the top of your forearm. You can have a friend do it while you close your eyes and see if you can tell when they touch your arm.

Here is a short article on fingerprints and how they enhance our sense of touch:

sense of touch

Answer 3:

Let me begin by saying that the skin on the palms of your hands and feet is different, which is why palms have "finger" prints. To the best of my knowledge, people aren't sure why the skin there is different, but there was an article in a respected science journal (think of a blog where scientists promote and publish their ideas) a couple years ago, that suggested fingerprints helped improve our ability to feel texture. That is, they make our sense of touch more sensitive.

On an interesting note, no one really knows why your fingers prune up when they get wet! It's actually a reflex! It's not that they just soak up water and buckle, like many people incorrectly believe. A recent scientific article in a respected science journal put forward the idea that the skin on your hands and feet prunes up and leads to better grip, particularly when wet. Although it's debated, this group suggested that the pruning skin acted like treads on a tire, and helped remove water while retaining better grip. However, it's just a hypothesis, and many people disagree.

Answer 4:

Fingerprints are a result of distinct ridges on the skin that do not change over time and are unique to each person. Even identical twins do not have the same fingerprints. Our fingerprints develop while we are still in the womb and may have evolved so we could grip things better. This may explain why prints are only on surfaces we use to grip items with, our fingers (and our evolutionary ancestors used their toes for gripping as well).

The fingerprints are produced from a layer in the skin called the papillary layer, which is a layer within the dermis layer of skin. It produces an extra thick layer to form the ridges of fingerprints. The papillary layer is found in all skin but only produces extra thick parts on the hand and feet and as a result those are the only areas with "prints."

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