The Indus valley civilization, the richest and the most ancient, originated around 2500 BC in the Indus river valley.It is thought that the valley was inhabited by Dravidians. Later, their descendants migrated to the far south of India. The inhabitants of the valley developed an urban culture which was based on commerce and sustained by agriculture. Ecological changes are generally attributed to the decline of the civilization. Pastoral, Aryan tribes migrated from North West into the subcontinent, during the 2nd millennium and they made the middle Ganges River valley as their abode. Their subsequent merger with their antecedent cultures resulted in a new milieu. The penetration of the Aryans to the east turned the northern India into a civilized land. In 500 BC, the inhabitants had acquired knowledge and made use of iron implements. In terms of political map, by then, there were too many independent states. As the population increased and people thrived with prosperity, there were disputes over boundaries. It was under Gupta Dynasty, also referred to as the golden period, when Hindu rule and religion saw its peak. As many as 16 dynasties (approx.), including the kingdoms of Magadha, Kosla, Kuru and Gandhara, rules the northern Indian plains by 600 BC.
Beginning 16th century, the rule of the Mughal dynasty continued for two hundred years. Meanwhile, in the south, Chola and Vijayanagar dynasties ruled (11th to 15th c.). In the 17th century the British East India Company established trading centers at Calcutta, Bombay and Madras. The British continued to expand and almost whole of present-day India, Pakistan and Bangladesh was under their rule by 1850s. The 1857 Mutiny in the north India led to transfer of political power from the East India Company to the British crown. Now Britain resorted to direct rule over most of India and partly through local rulers and treaties.