As the only species aware of its mortality, people have always had a morbid preoccupation with death. Our agrarian forefathers anthropomorphized their fear into the Grim Reaper, whose swipe symbolized the unexpected moment of life's end. Few of us own a scythe or know how to use one, but that swish still represents the surprise of hearing about someone's death and makes us tremble at the thought of how quickly we will pass into nonexistence. The now familiar Grim Reaper figure has outlasted four or five centuries, making appearances at costume balls and in New Yorker cartoons. He's forever...