I think we're terrified of being forgotten. I think that as soon as an ounce of intelligence entered our being, our first instinct was to scratch walls and make art out of sharp sticks and stones; We wanted it to be known that we were here.
Perhaps when Adam ate the Apple he was more relieved at being able to die than he was afraid of God's anger, perhaps even the Gods hate all this immortality business.
We are here to die. And perhaps the only reason we aren't relieved at that is because we might just forget to do anything but continue dying, we might just forget to live.
So here we are: scratching walls or ourselves, trying to make it become something other than our own coffins at the end of this journey.