An Arkansas couple was watching a program on the Discovery Channel about a
West African bush tribe whose men all had penises 24 inches long. When the
black male reaches a certain age, a string is tied around his penis and on
the other end is a weight. After a while, the weight stretches the penis to
24 inches.

Later that evening the wife looked at her husband, "How about we try the African string-and-weight thing?"

 The husband agreed, so they tied a string and a weight to his penis.

A few days later, the wife asked the husband, "How is our little tribal experiment coming along?"

"It looks like we're about half way there," he replied.

"Wow, you mean it's grown to 12 inches?"

"Not yet, but it's turned black."