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| Those pruney toes may have helped our ancestors get better footing in wet conditions, and today the wrinkles help us grip objects, scientists have found. CREDIT: Brian Chase / Shutterstock |
Fingers
may wrinkle when wet to help people grip wet objects, find researchers, who say
the pruney feature may have helped human ancestors do the same in wet
conditions. When a person's hands and feet are soaked in water, wrinkles
eventually develop on the tips of fingers and toes. Scientists once thought
this puckering resulted from the outermost layer of skin absorbing and swelling
with water, but recent studies revealed the nervous system actively controlled
this wrinkling by constricting blood vessels below the skin.
That
the nervous system controls this behavior suggests these wrinkles served a
purpose. Now researchers find these wrinkles could help fingers and toes grip
wet surfaces. "A phenomenon that everybody is familiar with is not just
some kind of side effect of the nature of the skin on fingers and toes, but a
functional feature that has very likely been selected for by evolution,"
researcher Tom Smulders, an evolutionary biologist at Newcastle University in
England, told LiveScience.
Smulders
and his colleagues had 20 volunteers pick up wet marbles and small lead weights
of different sizes. Volunteers attempted the task either with normal, dry hands
or after their fingers had wrinkled following a 30-minute soak in warm water.
The participants picked up wet items 12 percent faster with wrinkled fingers. "We
have shown that wrinkled fingers give a better grip in wet conditions,"
Smulders said. "It could be working like treads on your car tires, which
allow more of the tire to be in contact with the road, [which] gives you a
better grip." Another possibility is that wrinkling causes changes in skin
properties, such as its flexibility or stickiness, which help the fingers and
toes perform better when wet. "The most surprising thing to me was how the
effect was there in all 20 participants, independent of how fast they were on
average," Smulders said. "I never expected the effect to be so strong
and obvious."
As a
potential explanation of why this effect might have evolved, Smulders said,
"it could have helped with gathering food from wet vegetation or streams.
And as we see the effect in our toes, too, this may have been an advantage as
it may have meant our ancestors were able to get a better footing in the
rain." Wrinkled fingers apparently made no difference when it came to
picking up dry objects. "This raises the question of why we don't have
permanently wrinkled fingers, and we'd like to examine this further,"
Smulders said. "Our initial thoughts are that this could diminish the
sensitivity in our fingertips or could increase the risk of damage through
catching on objects."
Future
research should analyze what other primates or non-primate animals might also
show this phenomenon to shed light on when and why it evolved, Smulders said. "Which
other animals share this trait? And is the link among species that share it
phylogenetic — that is, they're all related — or environmental — that is, they
all deal with submerged objects, for example?" Smulders said.
The
scientists detailed their findings online Jan. 9 in the journal Biology
Letters.
Source: Live science
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