Solve Indian puzzles

An Indian chief had three wives, each of whom was pregnant. The first gave birth to a boy. The chief was so elated he built her a teepee made of deer hide. A few days later, the second gave birth, also to a boy. The chief was very happy. He built her a teepee made of antelope hide. The third wife gave birth a few days later, but the chief kept the details a secret. He built this one a two story teepee, made out of a hippopotamus hide. The chief then challenged the tribe to guess what had occurred.

Many tried, unsuccessfully. Finally, one young brave declared that the third wife had given birth to twin boys.

"Correct," said the chief. "How did you figure it out?"

The warrior answered, "It's elementary. The value of the squaw of the hippopotamus is equal to the sons of the squaws of the other two hides."