Chronology of Indus Valley Civilization

The Indus Valley Civilisation (IVC), also known as the Harappan Civilisation, represents one of the earliest urban cultures in world history. Flourishing primarily in the north-western regions of the Indian subcontinent, it extended across present-day Pakistan and north-western India, encompassing parts of Punjab, Sindh, Haryana, Gujarat, Rajasthan, and western Uttar Pradesh. The civilisation developed along the river systems of the Indus, Ravi, Sutlej, Beas, and Ghaggar-Hakra.
Archaeological and radiocarbon evidence divides the Indus Valley Civilisation into distinct chronological phases, each reflecting progressive social, technological, and cultural evolution. The generally accepted framework classifies its development into three major phases — Pre-Harappan (Early Phase), Mature Harappan (Urban Phase), and Late Harappan (Post-Urban Phase) — spanning approximately from 7000 BCE to 1300 BCE.

Pre-Harappan (Early Harappan) Phase — c. 7000 to 2600 BCE

The Pre-Harappan phase marks the formative period of the civilisation, during which early agricultural communities laid the foundations for urban development. This stage is often associated with the Neolithic and Chalcolithic cultures that preceded full urbanisation.
Key Features:

• Emergence of village settlements and agricultural practices in the north-western subcontinent.
• Domestication of animals such as cattle, sheep, and goats.
• Early evidence of wheat and barley cultivation.
• Development of mud-brick architecture, pottery, and rudimentary craft industries.
• Gradual introduction of copper tools and ornaments, marking the Chalcolithic transition.

Important Sites:

• Mehrgarh (Baluchistan): The earliest known farming settlement, dating to around 7000 BCE, showing evidence of agriculture, domestication, and trade.
• Kot Diji (Sindh) and Amri (Sindh): Proto-urban sites showing fortified settlements and early forms of pottery and craft specialisation.
• Kalibangan (Rajasthan): Early farming and habitation site with ploughed fields and rudimentary town planning.

This phase exhibits increasing social complexity, inter-regional trade, and technological advancement, setting the stage for full-scale urbanisation.

Mature Harappan Phase — c. 2600 to 1900 BCE

The Mature Harappan phase represents the zenith of the Indus Valley Civilisation and is often referred to as the Urban Phase. During this period, the civilisation achieved an unparalleled level of urban planning, economic organisation, and cultural uniformity.
Key Features:

• Well-planned cities built on a grid pattern with streets crossing at right angles.
• Division of cities into Citadel (fortified administrative or religious area) and Lower Town (residential zone).
• Use of baked bricks of standardised size for construction.
• Advanced drainage and sanitation systems with covered drains, soak-pits, and private baths.
• Emergence of large granaries, warehouses, workshops, and dockyards, suggesting centralised control and surplus production.
• Standardised weights and measures, indicative of regulated trade and administration.
• Extensive trade networks both internal and external, linking the Indus cities with Mesopotamia, Oman, and Bahrain.
• Development of the Indus script, used on seals and pottery, though still undeciphered.
• Use of steatite seals engraved with animal motifs (unicorn, bull, elephant, etc.) for commercial and administrative purposes.
• Flourishing of crafts and industries such as bead-making, metallurgy, pottery, and textile production.

Major Urban Centres:

• Harappa (Punjab, Pakistan): Administrative and industrial centre with granaries and citadel structures.
• Mohenjo-daro (Sindh): The largest and most well-planned city, featuring the famous Great Bath, drainage systems, and residential complexes.
• Dholavira (Gujarat): Known for sophisticated water management, reservoirs, and unique city layout.
• Kalibangan (Rajasthan): Evidence of fire altars and ploughed fields.
• Lothal (Gujarat): Noted for its dockyard and trade with Mesopotamia.
• Banawali (Haryana): Agricultural settlement with evidence of trade and crafts.

The Mature Harappan period saw a highly centralised and peaceful society with little evidence of warfare. The uniformity of weights, measures, bricks, and urban layouts across a vast geographical area suggests an efficient system of governance and cultural cohesion.

Late Harappan (Post-Urban) Phase — c. 1900 to 1300 BCE

The Late Harappan phase marks the decline and disintegration of the Indus urban centres. Urbanism gradually gave way to rural, agrarian lifestyles, and regional cultural variations began to emerge.
Key Features:

• Decline of large urban centres like Mohenjo-daro and Harappa.
• Abandonment or shrinking of cities due to environmental and socio-economic factors.
• Shifts in settlement patterns from the Indus River basin towards the Ganga-Yamuna plains.
• Simplification of pottery styles and material culture.
• Gradual disappearance of standardised weights, measures, and script.
• Continuation of some Harappan traditions (pottery, agricultural practices) in modified forms in regional cultures.
• Increased use of painted grey ware and ochre-coloured pottery in later sites.

Important Late Harappan Sites:

• Rangpur (Gujarat): Agricultural settlement showing continuity from Mature Harappan times.
• Ropar (Punjab): Late Harappan levels showing interactions with post-Harappan cultures.
• Surkotada (Kutch): Evidence of horse remains and continued occupation during the decline phase.
• Alamgirpur (Uttar Pradesh): Easternmost Harappan site showing expansion towards the Ganga plains.

Causes of Decline

The decline of the Indus Valley Civilisation remains a subject of scholarly debate. Several interrelated factors likely contributed to its collapse:

• Environmental Changes: Shifts in river courses, particularly the drying up of the Ghaggar-Hakra (Saraswati) River system, may have disrupted agriculture.
• Floods or Droughts: Climatic fluctuations causing floods or prolonged droughts could have led to famine and migration.
• Decline in Trade: Reduction in external trade with Mesopotamia and internal economic stagnation weakened urban economies.
• Sociopolitical Disintegration: Loss of central authority and urban coordination contributed to the breakdown of civic life.
• Invasions or Migrations: Theories suggest movements of Indo-Aryan groups into the subcontinent, though this remains debated.