Is the human body (and other life forms animal/plant) programed/designed to kill itself?
Well that appears to be the case in every species of animal and plant life, the pattern of time of gestation and or birth, growth from infancy, childhood, adolescent, youth, middle age, old age, predeath and death and is variable but species specific as long early death does not happen due to unnatural causes. There appears to be a genetic code governing the evolution from conception/birth to death. Only avenues in practice are mainly to prevent premature death. On experimental basis in flies research is in progress to increase the age, but all that is far from application to humans.