Three American anthropologists head to an island...

inhabited by a group of indigenous cannibals, in order to study the native culture. While filming the natives, the three men are captured by a savage hunting party are returned to the native's village.
The Americans are told by the chief that they have one chance to save their lives. Each person must go into the jungle and bring back whatever fruit they can find. If they don't return, a hunting party will find them and skin them alive.
The first anthropologist runs into the jungle to find fruit. He quickly returns with a bushel of apples within hours.
The chief then tells his people that the American must put all of the apples that he brought back in his own anus. If the American makes any facial expression whatsoever, he will be killed and eaten.
The American hesitates, then starts to shove the apples in his own anus, one by one. He gets two of the five apples in, but winces in pure agony on the third.
The natives kill him and begin to cook him, when the second man returns, with a handful of berries. The chief explains what the man must do. Without hesitation the American starts putting the berries in his anus. He puts in three. Five. Seven. He has one berry left, but then out of nowhere he starts laughing.
The natives are confused, but since he broke the rule, he is immediately killed.
In heaven, the first anthropologist meets up with the second one. He says, "Dude, you were so close! You could have survived! Why on earth did you laugh?"
The second guy chuckles and says, "I saw our buddy returning with pineapples."