According to the passage, what is the oldest known civilization of India?
Comparable to the decline of the great Mayan culture, the fall of the ancient Indus Valley people yields interesting information about their daily lives. It seems that this civilization is the oldest recorded civilization in India, yet many of their practices seem advanced. For example, there is evidence of careful and creative design of bathroom facilities, including sewage disposal. What is evident in other ancient societies seems to be missing from the Indus Valley one, namely social conflict, slavery, armed forces, and various vices. The cause of their sudden demise is a mystery.