One night, as the farmer and his wife were reading in bed, he looked up from his copy of "Animal Husbandry" and said, "Did you know that humans are the only species in which the female achieves orgasm?"
She gazed back at him hopefully, smiled, and said, "Really? Prove it!"
He frowned, said, "Okay". Then left the bedroom.
An hour later, he returned, all tired and sweaty, and said: "I know that the cow and the sheep didn't, but the way that pig keeps squealing, it's hard to tell!"
