Settlements
From the beginning of the 4th millennium BC, the individuality of the early village cultures began to be replaced by a more homogenous style of existence. By the middle of the 3rd millennium, a uniform culture had developed at settlements spread across nearly 500,000 square miles, including parts of Punjab, Uttar Pradesh, Gujarat, Baluchistan, Sind and the Makran coast.

This earliest known civilisation in India, the starting point in its history, dates back to about 3000 BC. Discovered in the 1920s, it was thought to have been confined to the valley of the river Indus, hence the name given to it was Indus Valley civilisation. This civilisation was a highly developed urban one and two of its towns, Mohenjodaro and Harappa, represent the high watermark of the settlements. Subsequent archaeological excavations established that the contours of this civilisation were not restricted to the Indus valley but spread to a wide area in northwestern and western India. Thus this civilisation is now better known as the Harappan civilisation. Mohenjodaro and Harappa are now in Pakistan and the principal sites in India include Ropar in Punjab, Lothal in Gujarat and Kalibangan in Rajasthan.

Urban Development
The emergence of this civilisation is as remarkable as its stability for nearly a thousand years. All the cities were well planned and were built with baked bricks of the same size; the streets were laid at right angles with an elaborate system of covered drains. There was a fairly clear division of localities and houses were earmarked for the upper and lower strata of society. There were also public buildings, the most famous being the Great Bath at Mohenjodaro and the vast granaries. Production of several metals such as copper, bronze, lead and tin was also undertaken and some remnants of furnaces provide evidence of this fact. The discovery of kilns to make bricks support the fact that burnt bricks were used extensively in domestic and public buildings.

Occupations
Evidence also points to the use of domesticated animals, including camels, goats, water buffaloes and fowls. The Harappans cultivated wheat, barley, peas and sesamum and were probably the first to grow and make clothes from cotton.Trade seemed to be a major activity at the Indus Valley and the sheer quantity of seals discovered suggest that each merchant or mercantile family owned its own seal. These seals are in various quadrangular shapes and sizes, each with a human or an animal figure carved on it. Discoveries suggest that the Harappan civilisation had extensive trade relations with the neighbouring regions in India and with distant lands in the Persian Gulf and Sumer (Iraq).

Society and Religion
The Harappan society was probably divided according to occupations and this also suggests the existence of an organized government. The figures of deities on seals indicate that the Harappans worshipped gods and goddesses in male and female forms and has also evolved some rituals and ceremonies. No monumental sculpture survives, but a large number of human figurines have been discovered, including a steatite bust of a man thought to be a priest, and a striking bronze dancing girl. Countless terra-cotta statues of Mother Goddess have been discovered suggesting that she was worshipped in nearly every home.

By about 1700 BC, the Harappan culture was on the decline, due to repeated flooding of towns located on the river banks and due to ecological changes which forced agriculture to yield to the spreading desert. Some historians do not rule out invasions by barbarian tribes of the northwest as the cause of the decline of the Harappan civilisation. When the initial migrations of the Aryan people into India began about 1500 BC, the developed Harappan culture had already been practically wiped out.