Wrinkled Fingertips Enhance Grip

black and white photo of a wrinkled hand

Biological Strategy

Humans

Eleanor Banwell

Image: Isaac Fryxelius / Pixabay / CC BY NC - Creative Commons Attribution + Noncommercial

Attach Temporarily

Living systems must sometimes, temporarily, stay in one place, climb or otherwise move around, or hold things together. This entails attaching temporarily with the ability to release, which minimizes energy and material use. Some living systems repeatedly attach, detach, and reattach for an extended time, such as over their lifetimes. Despite being temporary, these attachments must withstand physical and other forces until they have achieved their purpose. Therefore, living systems have adapted attachment mechanisms optimized for the amount of time or number of times they must be used. An example is the gecko, which climbs walls by attaching its toes for less than a second. Other examples include insects that attach their eggs to a leaf until they hatch, and insects whose wings temporarily attach during flight but separate after landing.

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Capture, Absorb, or Filter Solids

Some living systems must secure solid particles such as sediment, usually to keep the particles from hindering their health or activity. The most common way in which they do this is through filtering. To be effective, a filtering system must be appropriate to the sizes of solid particles to be captured and must capture only what is needed. It must also be effective in the appropriate media–air, water, or sometimes solids like soil. An example is mangroves, which are trees that grow along ocean coasts. Their root system slows down and settles sediment out of the water, building up soil to support the mangrove ecosystem.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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Fingertips of primates enhance grip in wet conditions by wrinkling

We all know that our fingertips and toes wrinkle if they stay wet for around five minutes or more. Less well known is that this is an active response triggered by our nerves and that if those nerves are damaged, it stops. The wrinkles that appear in our fingers and toes have a very distinctive pattern that corresponds with the most efficient topography for moving water out of the way.

The grooves and ridges that form when our fingers, and the fingers of other primates, become wet mean that, first, a small area of skin makes contact with the surface the fingers are gripping. Like the treads of a tire, the grooves channel the water out the way. Unlike the treads of a tire, our finger pads are soft and so we are able to continue to increase the area of contact, reducing the size of the grooves as pressure increases and the water is cleared.

This active increase in grip in response to moisture makes sense in species that regularly climb on damp and rainy surfaces like trees and rocks.

Image: Llorenzi / CC BY SA - Creative Commons Attribution + ShareAlike

Image: Isaac Fryxelius / Pixabay / CC BY NC - Creative Commons Attribution + Noncommercial

A child's wrinkled right hand.

Last Updated July 23, 2019

References

Journal article

Are Wet-Induced Wrinkled Fingers Primate Rain Treads?

Brain Behav Evol | 01/01/2011 | Changizi M, Weber R, Kotecha R, Palazzo J

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