Dr. Science weighs in:
It’s often said that humans are the only creatures who know they’re going to die, but I think it’s more important that we’re the only ones who know we’re going to get old, too old to find all our own food. When other creatures — even other apes — get too old to feed themselves consistently, they die. Animals have no old age in our sense, because every adult is self-supporting: if you get too old to take care of yourself, that’s pretty much it.