It’s a common experience: stay too long in the shower, and your fingers become wrinkly. But could these wrinkly fingertips have evolutionary significance? A recent paper suggests that they could, pointing out that cutting a sympathetic nerve to a finger eliminates the wrinkling response. This means purely osmotic interactions do not fully explain these wrinkles.
|The wrinkles, as observed in humans (a) and macaques (b).|
The authors analyzed pictures of wrinkled fingers from different people, and discovered that these wrinkles have a structure typical of drainage networks. Drainage networks include river basins, and, more importantly, rain treads on tires. These rain treads were specifically designed to reduce slippage when driving on wet roads. Thus, the structure of the wrinkles could help maintain a good grip in wet conditions – on tree bark, for example, which would have been essential for our primate ancestors.
|Rain treads on tires.|
Changizi M, Weber R, Kotecha R, Palazzo J (2001). "Are wet-induced wrinkled fingers primate rain treads?" Brain Behav Evol 77:286-290