I remember I stopped dead in my tracks. I had been walking along the flat, dark shale bed of the ravine behind my grandfather’s farmhouse in southern Indiana. There on the ground, still in perfect alignment, lay the skeleton of a cow that had wandered away one winter many years ago and had slipped and fallen into the ravine. The bones lay in precise order—the head bone connected to the neck bone, the neck bone connected to the back bone, and so on.