The Last American Man by Elizabeth Gilbert

By the time Eustace Conway was seven years old, he could throw a knife accurately enought to nail a chipmink to a treeee. By the time he was ten, he could hit a running squirrel at fifty feet with a bow and arrow. This amazing man, at seventeen, moved out of his family's home and headed into the mountains, where he lived in a teepee of his own design, made fire by rubbing two sticks together, bathed in icy streams, and dressed in the skins of animals he had hunted and eaten.