No effort. No allergies. No cleanup. In the early 1970s, Gary Dahl, a freelance advertising copywriter, was having drinks at a bar with friends when the conversation turned to the destructive nature of pets. Dogs and cats chewed and clawed. Gerbils need to live in packs of 2 or more. Pet fish means regular cleaning of the tank. Then there was the fact that pets required constant attention—they must be walked, played with, fed, and cleaned up after. Dahl said he didn’t have to worry about that because he had a “pet rock.” ….