A young boy had been taken for his first visit to a nudist camp by his parents.
He was surprised at the different sizes of the male organs and mentioned it to his father.
The father, being rather well endowed, explained that it was a measure of intelligence, the big ones being smart and the small ones being dumb.
That afternoon the father was looking for his wife and asked his son if he had seen his mother.
"I saw her about ten minutes ago, She was with a real dumb man, but he seemed to be getting smarter all the time."