We have very little information about the religious life of the Indus valley people. During it's hey days the Indus valley civilization covered an area in the Indian subcontinent that was larger than the present day Europe. The civilization flourished roughly between 3500 BC and 2000 BC, with its antecedents dating as far back as 7000 -6000 BC during the Neolithic period.
The Indus valley civilization was essentially an urban civilization, characterized by well planned cities, built according to the needs of the people who inhabited them and the geographical and climatic challenges they faced. They built high rise structures, knew agriculture, pottery and metallurgy, familiar with drainage and water supply systems and traded with other peoples by navigating in boats along the river routes and also probably across the seas.
Indus Valley Seal The discovery of Indus valley civilization brought the Indian subcontinent into limelight as home to one of the most ancient human civilizations and gave scope to many scholars to present an argument that the Indian subcontinent, as a land of racial, ethnic and linguistic diversity from time immemorial and as a land that stood in the way of waves of migrating prehistoric nomads and adventurers of stone age, might be the cradle of human civilization. While it is true that the Harappn and Mohenjodaro cities might have flourished around 3000 BC, the fact that they were well planned cities lends credence to the argument that the urban planning and the level of sophistication that went into its execution, could not have been possible without corresponding development in various fields spread over a period of several centuries. It is debatable whether the technology and the knowledge that went into the construction of such great cities was wholly indigenous or foreign. Some aspects of our knowledge of base numbers, metallurgy, astrology and some elements of Hinduism, yoga and others schools of philosophy might have been part of the legacy left by this great and mysterious civilization, about which we presently know so little.
The Indus valley civilization is now increasingly referred to as Sindhu Saraswathi Civilization. This is based on the consensus opinion among many Indologists that the Indus valley civilization was probably part of Vedic civilization or not much different from it, an idea that also confronts and repudiates the classical Aryan invasion theory in support of the hypothesis that both the Indus and Vedic cultures were established by indigenous people, some of whom might have even migrated to areas outside the Indian subcontinent and played their role in the development of independent civilizations as far away as Greece and Europe.
Whatever may be the truth, the Indus people built a vast civilization that disappeared mysteriously by 1800 BC and was replaced by Vedic culture in parts of India. They had knowledge of a written script which is yet to be deciphered and which they used in their seals. About 500 such seals were found at various Indus sites. We do not know for what specific purpose they were used. It is possible that the Indus people might have used them to mark their merchandise, as emblems of authority or as tokens of commercial contracts. The seals, along with other artifacts such as stone statues and terracotta figures, provide some clues about the religious beliefs of the Indus people based on which we can draw the following conclusions.