Exponential decline late in life (we don't just go downhill. we pick up speed.)
Regarding the exponential decline in the body late in life, we believe that we know the evolutionary reason based on life history theory, but not really the proximate explanations. Do systems (organs, tissues) have a certain level of resiliency, evolved dependent on life history, that “gives way” late in life? Does somatic maintenance ever really wane, or was regular maintenance only good enough to get an animal’s body so far?