Other ideas I've had about evolutionary traits. I don't know if they are common knowledge anyway:
- The horrible feeling of scratching your nails on a blackboard, which sets your teeth on edge, must be a protection against damaging your teeth or nails on stones when biting or scratching in the ground for food.
- The start when falling asleep (technical term ...) forces you to check that you are not in a position to fall out of bed, or - way back - to fall out of the branches of a tree in which you are nesting.
- Could stentorian snoring have had a purpose as a scary sound to keep other creatures out of caves where humans were sleeping?