A joke that proves blonds are smart

A guy was seated next to a blond girl on an airplane. Being bored, he turned to the girl and said, "Let's talk. I''ve heard that flights go quicker if you strike up a conversation with your fellow passenger." The girl, who was reading a book, closed it slowly and said to the guy, "What would you like to talk about?" Oh, I don't know," said the guy. "How about nuclear power?" "OK," she said. "That could be an interesting topic. But let me ask you a question first. A horse, a cow and a deer all eat the same stuff... grass. Yet a deer excretes little pellets, while a cow turns out a flat patty, and a horse produces clumps of dried grass. Why do you suppose that is?" The guy thought about it and said, "Hmmm, I have no idea." To which the girl replied, "Do you really feel qualified to discuss nuclear power when you don''t know shit?"