A civil engineer

A civil engineer, a chemist and an economist are traveling in the countryside.

Weary, they stop at a small country inn. "I only have two rooms, so one of you will have to sleep in the barn," the innkeeper says.

The civil engineer volunteers to sleep in the barn, goes outside, and the others go to bed. In a short time they're awakened by a knock.

It's the engineer, who says, "There's a cow in that barn. I'm a Hindu, and it would offend my beliefs to sleep next to a sacred animal."

The chemist says that, OK, he'll sleep in the barn. The others go back to bed, but soon are awakened by another knock.

It's the chemist who says, "There's a pig in that barn. I'm Jewish, and cannot sleep next to an unclean animal." So the economist is sent to the barn.

It's getting late, the others are very tired and soon fall asleep. But they're awakened by an even louder knocking.

They open the door and are surprised by what they see: It's the cow and the pig!