to the person who asked about death being necessary: death by ageing is caused by deterioration of the telomeres that cap chromosomes, which means that eventually the cells aren't able to divide anymore, so they die. it's called cell senescence (and some cells like rat brain cells don't have this problem and they can keep on dividing forever). so it is possible that in the future we could maybe prevent death, by altering DNA so that the telomeres don't go bad. (telomeres shorten after each cell replication). I don't know if you'll post this but I think it's cool info that people don't hear about unless they search for it specifically