Do pruney fingers grip better?
Fingers and toes will eventually wrinkle if immersed in water for long enough. The question is why?
In a 2011 article, Dr. +Mark Changizi
(currently Director of Human Cognition at the recently formed 2AI labs in Boise Idaho) and his student Romann Weber postulated “Are Wet-Induced Wrinkled Fingers Primate Rain Treads?” In the article he noted that “nearly a century ago surgeons observed that no wrinkling occurs if a nerve to the finger has been cut” ruling out the idea that wrinkling arises from some kind of local reaction to water. This led the team to postulate leading to the idea that that pruney fingers could actually be a selected evolutionary trait that enhances your ability to handle wet objects. They backed up the idea by comparing to efficient drainage networks and the designed grooves on modern tires. (Original article: http://www.karger.com/Article/FullText/328223
After Changizi’s article was published, Ed Yong at the journal Nature
wrote “The ultimate test of the hypothesis will be to see if people with wrinkled fingers are better at gripping in wet conditions." (Ref: http://www.nature.com/news/2011/110628/full/news.2011.388.html
). A subsequent study appeared to back up the idea (http://www.bbc.co.uk/news/science-environment-20951232
). Sounds like a wrap, right?
Not so fast! Now, a new research group at the Max Delbrück Center for Molecular Medicine in Germany has published a paper in PLoS with the very clear title "Water-Induced Finger Wrinkles Do Not Affect Touch Acuity or Dexterity in Handling Wet Objects."http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0084949
Co-lead authors Julia Haseleu and Damir Omerbašić compared the dry and wet dexterity of a much larger group of volunteers through a greater variety of tasks, more than doubling both the number of test subjects and types of tasks over the previous study. On average, there was no statistical difference between how fast the two groups finished their tasks. Consequently, there’s no evidence based on their data to say that pruney fingers will give any evolutionary gripping advantage in wet environments. Instead, they suggest that finger wrinkling is simply coincidental with another autonomic nervous response: vasoconstriction
– the contraction of blood vessels in response to environmental stimulation such as cold, or water immersion.
Let the pruney finger debate rage on!
Image from http://en.wikipedia.org/wiki/File:Wrinkly_fingers.jpg
used for non-commercial purposes under the
CC BY-NC: "Fir0002/Flagstaffotos".