View full lesson: http://ed.ted.com/lessons/pruney-fingers-a-gripping-story-mark-changizi
Why do fingers become pruney when they get wet? Likely, for the same reasons that tires have treads. Mark Changizi examines the evolutionary reasons for pruney fingers, while exploring natural and manmade phenomena, like river networks, that operate similarly.
Lesson by Mark Changizi, animation by Lippy.