Why Do Fingers, Toes Prune Fast When Soaked in Water? Evolution May Have the Answer

Everyone must have experienced the wrinkles that develop on their fingers and toes when soaked in water for an extended period. It resembles a prune that seems to have no use at all.

But have you ever wondered how and why it happens? Scientists have an explanation about it and proposed a possible reason it happens. Some even say that it is an example of the brilliance of human evolution.

How Fingers Prune Underwater

According to Medium, the skin has many layers. The top layer is called the epidermis, followed by the dermis, where smaller blood vessels, nerves, sweat glands, and hair roots are located. Its bottommost layer is called the subcutaneous layer, where larger blood vessels and nerves, as well as fat and connective tissue, are found.

The epidermis, the outer layer of the skin, wrinkles when exposed to water for a prolonged period. Deeper into the skin, the epidermis is also divided into four layers: stratum corneum, granular layer, squamous cell layer, and basal cell layer.

Harvard Health Publishing reported that wrinkling happens at the top layer of the epidermis or the stratum corneum. This layer is like a sponge that absorbs water when it is immersed. It gets softer and more pliable as it expands when underwater for a prolonged period to compensate for the increased volume of fluid and to return to its original position.

However, the wrinkles are most notable in fingers, toes, and the undersides of hands and feet because the stratum corneum is thicker on these areas compared to other areas of the skin.

As to what purpose it has or if it does have any purpose at all, scientists have also formulated some theories, which included human evolution.

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Why Fingers Prune Underwater

Neuroscientist Mark A. Changizi said that some people might see pruning of fingers as unnecessary, but this mechanism is an example of the beauty of human evolution, NBC News reported.

Toes could prune even when not soaked in a bubble bath. Just walking around in bare feet on wet, damp grass also causes the epidermis to wrinkle as if it were submerged in water.

Changizi studies how hands work, and that includes why fingers and toes prune up when soaked underwater. He said that pruning of fingers and toes is not just some simple physical reaction. It could have been designed for a good reason throughout the evolution of humans.

In his 2011 report in the journal Brain, Behavior and Evolution, he argued that the epidermis in the toes and fingers prune because of two things. First, they create channels to help drain the water away. Secondly, it was designed to prevent slipping. He emphasized that some people have pruned skin all over their wet feet to provide them with greater skid-proof characteristics.

He added that wet fingers transform from being racing tires to all-weather tires with treads for traction. Chingizi believes that shoe and tire manufacturers could learn from the design skills of evolution from which all humans benefited.