Anyone who has ever squirmed through a dental cleaning can tell you how sensitive teeth can be. This sensitivity gives important feedback about temperature, pressure—and yes, pain—as we bite and chew our food. However, the sensitive parts inside the hard enamel first evolved for something quite different.
I beg your pardon
Swim bladders evolved from lungs. You wouldn’t think that something that makes the fishies better ocean divers originally evolved to let them breathe air.