The Indus civilization, an ancient civilization in South Asia, existed from about 2700 to 1750 BC. It is sometimes referred to as the Harappa civilization; one of its major centers. It stretched from north of the Hindu Kush down the entire length of the Indus and beyond into peninsular India. The Indus civilization is known only from archaeological evidence. Its origins traditionally were viewed as the result of the diffusion of farming and technology from more advanced cultures in Mesopotamia and on the Iranian plateau to Baluchistan and ultimately to the Indus Valley. One of the most important centers of Indus civilization was Mohenjo-Daro, situated along the west bank of the Indus River. Like most cities of the Indus civilization, it consisted of two major areas of occupation: a high citadel to the west and a lower city of domestic dwellings to the east. The Indus people supported themselves by irrigation-based agriculture. They grew domesticated rice, wheat, and barley, and they may have cultivated dates and cotton. Among the first people in the world known to have kept chickens, they also had dogs, buffalo, and humped cattle. They may also have domesticated pigs, horses, camels, and, possibly, elephants.
The Aryan was a tribal and nomadic people who lived far away in Euro-Asia. They were unquestionably tough people and they were fierce and war-like. So their culture was oriented around warfare, and they were good at it. The Aryans first settled along the Indus River, in the same place where the Harappa people had lived. They settled down and mixed with the local Indian people. They lived there from about 1500 to 800 BC. It seems to be at this time that the caste system began in India. It was the Aryans who developed Hinduism, and also the classical language of Sanskrit. Aryans created four main castes. The top castes were made up of priests, kings, and warriors. The lowest caste was made up of workers who served the higher