Indus Valley Civilization (IVC) — Complete UPSC Notes

1. Discovery & Overview

The IVC was rediscovered through systematic archaeology — the civilization had been completely forgotten for over 3,000 years until the 19th–20th century. Its discovery fundamentally changed understanding of South Asian prehistory, pushing back the origins of urban culture in the subcontinent by nearly two millennia.

2. Geographical Extent & Phases

The IVC covered approximately 1.5 million sq km — larger than the combined area of Egypt and Mesopotamia, making it the largest of the four early urban civilizations by geographical spread. Over 2,600+ sites have been identified (as of 2024).

Extreme Points

Three Phases of IVC

3. Major Sites

4. Town Planning

The IVC's town planning is its most celebrated achievement — a level of urban sophistication not seen again in the subcontinent until the colonial period. Cities were laid out on a grid with remarkable uniformity across sites separated by 1,500 km.

Grid Streets and Two-Part Layout

• Two-part layout: Every major IVC city was divided into (1) a raised Citadel (western mound) housing public/administrative/ritual structures; (2) a larger Lower Town (eastern mound) for residential and commercial use. Exception: Dholavira had a 3-part plan (Citadel + Middle Town + Lower Town).
• Grid street pattern: Streets intersected at right angles (cardinal directions). Main streets (9–10 m wide) ran north-south or east-west; cross streets (1.5–3 m wide) served residential blocks.
• Standardized burnt bricks: Ratio 1:2:4 (thickness:width:length) used across the entire civilization — e.g., 7×14×28 cm. Kiln-fired (not sun-dried), water-resistant. This ratio across 1,500+ km is remarkable evidence of centralized authority or strong trade convention.
• No windows on main streets: Houses opened onto lanes, not main streets — for privacy and dust control. Ventilation via internal courtyards.
• Wells: Each house had its own well; community wells lined the streets. Mohenjo-daro had over 700 wells.
• Garbage bins: Terracotta bins at street corners — evidence of civic sanitation management.

The Great Bath (Mohenjo-daro)

• Construction: Floor and sides of finely fitted burnt bricks; floor laid with bitumen (natural asphalt) to prevent leakage — earliest known use of bitumen as a waterproofing agent in construction.
• Access: Two staircases (north and south ends) descending into the pool; a corbelled drain at the south-west corner for emptying.
• Surroundings: Colonnaded verandah on all sides; changing rooms around the verandah; a large well to the east supplied fresh water.
• Purpose: Almost certainly ritual/religious purification — located in the citadel (ritual/administrative zone). Marshall compared it to Hindu ritual bathing tanks (pushkarini).
• Unique: No comparable structure exists in any other Bronze Age civilization of the period.

The Granaries

• Harappa Granary: Two rows of 6 granaries (12 total); floor plan ~50×40 m; air ducts beneath the floor (ventilation); nearby workers' barracks found — evidence of organized labour.
• Mohenjo-daro Granary: The largest single building of the entire IVC (54.86 m × 36.6 m); divided into 27 blocks; in the citadel area. Wheeler identified these as state grain stores suggesting centralized taxation/redistribution economy — now questioned by later archaeologists (no grain found in situ at most).

The Drainage System

• Underground drains: Every street had a covered brick-lined drain; covered with corbelled bricks or stone slabs (removable for cleaning).
• Manhole inspection: Manholes provided at intervals for inspection and desilting — showing long-term maintenance planning.
• House connection: Every house had a private drain connected to the street drain through a soakpit.
• Hierarchy: House drains → lane drains → main street drains → large collector/trunk drains → city outfall. A fully engineered drainage network.
• Comparison: No other Bronze Age civilization (Egypt, Mesopotamia, China) had an equivalent city-wide covered underground drainage system.

5. Economic Life

Agriculture

• Main crops: Wheat and barley were the primary staples; evidence from Harappa, Mohenjo-daro, Banawali.
• Cotton: IVC was the first civilization in the world to cultivate cotton. Greeks called it sindon (from Sindh). Cotton threads found on a silver vase at Mohenjo-daro.
• Rice: Found at Lothal and Rangpur (Gujarat) — not the primary crop; evidence of early rice cultivation in IVC.
• Other crops: Dates, sesame (large deposit at Banawali), mustard, peas, lentils, jowar, ragi, melon.
• Plough marks: Kalibangan (Pre-Harappan level) shows the earliest ploughed field in the world — two sets of furrows at right angles indicating simultaneous two-crop planting.
• Tools: No iron tools; stone blades, copper axes, wooden ploughs (scratch plough), chert sickles.

Trade with Mesopotamia — "Meluhha"

• Lothal dockyard: The world's first known tidal dock (222×37 m) with a sluice gate system to maintain water level regardless of tides — sophisticated hydraulic engineering for organized maritime trade.
• Shortugai (Afghanistan): An IVC colony/trading post near lapis lazuli mines — IVC controlled the supply chain of lapis lazuli traded to Mesopotamia.
• Sutkagendor: Persian Gulf–coast trading post on Makran coast — gateway for maritime trade.
• Goods exported: Carnelian (etched) beads, lapis lazuli, copper, timber, cotton textiles, ivory, shell objects, gold.
• Goods imported: Tin (from Afghanistan/Central Asia — needed for bronze alloy), silver (Afghanistan, Iran), gold (Kolar, Karnataka or Afghanistan).
• Currency: No coins — trade was by barter; standardized weights served as a universal measure of exchange value.

Weights and Measures

• Material: Chert (crypto-crystalline silica) — cubical weights, perfectly polished, found across all major sites.
• Binary-decimal system: Lower values used binary progression: 1, 2, 4, 8, 16, 32, 64; higher values used decimal progression: 160, 200, 320, 640. This dual system is unique.
• Uniformity: Identical weight ratios at Harappa, Mohenjo-daro, Lothal, Chanhudaro, and other sites — the most compelling evidence of a centralized authority governing the entire civilization.
• Measuring rods: Shell measuring rods at Mohenjo-daro; ivory scale at Lothal (smallest division: 1.7 mm — comparable to modern precision instruments); bronze rod at Harappa.

Bead Industry and Seals

• Bead industry: Extraordinarily sophisticated — carnelian (etched), lapis lazuli, steatite, shell, gold, faience beads. Chanhudaro and Lothal were bead-making centres. IVC etched carnelian beads found in royal graves at Ur (Mesopotamia) — direct evidence of trade contact.
• Seals: Over 4,000 identified; primarily square steatite (2.5–5 cm) with perforated boss on reverse. Most common animal: Unicorn (~70% of all seals). Other animals: zebu bull, elephant, tiger, rhinoceros, crocodile. Used for trade (stamping bales), administrative identity, and amulets.
• Pashupati Seal: Found at Mohenjo-daro; depicts a three-faced, cross-legged figure in yogic posture with a horned headdress, surrounded by four animals — elephant, rhinoceros (right), buffalo, tiger (left); two deer below. Marshall identified the figure as "proto-Shiva" or Pashupati (Lord of Animals).

6. Social Life & Religion

Social Life

• Social stratification: Evidence suggests class differentiation — some houses significantly larger than others; elite residences near citadel; workers' quarters near Harappa granary. However, stratification appears moderate compared to Egypt/Mesopotamia — no extreme wealth in royal tombs.
• Craft specialization: Distinct artisan quarters — potters' kilns, bead-making workshops (Chanhudaro, Lothal), copper-smithing areas; developed division of labour.
• Clothing: Cotton and wool garments; shawl-like garment worn over one shoulder (as depicted on "Priest-King" bust).
• Ornaments: Both men and women wore ornaments — necklaces, bangles, earrings, finger rings, anklets; made of gold, silver, copper, faience, terracotta, shell, semi-precious stones.
• Burial practices: Extended burial (most common) — body in rectangular pit, head pointing north, feet south, with grave goods (pottery, ornaments). Fractional burial and pot/urn burial also found. Double burial at Lothal (man + woman buried together — interpreted as possible sati, not conclusive). Cemetery-H (Late Harappan): different burial traditions with painted pottery motifs — possibly a new population group.
• Bronze Dancing Girl (Mohenjo-daro): A 10.5 cm bronze statuette of a young woman in a confident pose; cast by lost-wax (cire perdue) technique; shows mature artistic confidence. Now in National Museum, New Delhi.
• "Priest-King" bust (Mohenjo-daro): 17.5 cm steatite bust; trefoil-patterned robe; eyes half-closed (meditative). Tentatively identified as a priest-king or administrator. Now in National Museum of Pakistan, Karachi.

Religion

• No identified temple: Unlike Mesopotamia and Egypt, no building at any IVC site has been definitively identified as a temple — one of IVC's most striking features. Religion appears to have been practiced at home, at open-air fire altars, and possibly at the Great Bath.
• Mother Goddess worship: Over 2,000 terracotta female figurines found — the most common religious object; often with elaborate headdresses; many depict pregnancy; interpreted as a fertility/mother goddess cult.
• Pashupati (Proto-Shiva) worship: The Pashupati Seal (Mohenjo-daro) shows a three-faced, cross-legged, ithyphallic figure in yogic posture surrounded by four animals. Marshall identified the figure as proto-Shiva/Pashupati — suggesting continuity between IVC religion and later Shaivism.
• Phallus (lingam) and ring stones (yoni): Numerous stone phalluses and perforated ring stones found — widely interpreted as Shiva-lingam and yoni worship; evidence of proto-Shaiva religion.
• Tree worship: Pipal tree depicted on seals and tablets (a deity or spirit stands in a pipal tree; a kneeling worshipper below). Pipal is still sacred in Hinduism/Buddhism — long continuity.
• Fire worship: Fire altars found at Kalibangan (on the citadel — 7 fire altars in a row with ash and animal bones), Lothal, and Banawali — earliest evidence of fire worship/ritual in South Asia.
• Water worship: The Great Bath suggests ritual bathing as a purification rite; water clearly had a sacred dimension.

7. Indus Script

• Signs: ~400–600 distinct signs (scholars disagree on the exact count); this number is consistent with a logosyllabic script (like Sumerian cuneiform or Chinese), not a pure alphabet (~20–30 signs) or pure syllabary (~50–100 signs).
• Direction: Written predominantly right-to-left; some inscriptions show boustrophedon (alternating right-to-left and left-to-right) — similar to early Greek writing.
• Inscription length: Most inscriptions on seals have only 4–5 signs; the longest known inscription has only 26 signs — making statistical/frequency analysis very difficult.
• No bilingual text: No Rosetta Stone equivalent has been found — the main barrier to decipherment.
• Where found: Seals (most common), pottery graffiti, copper tablets, bronze objects, ivory rods, terracotta tablets.

Decipherment Attempts

8. Decline Theories

The decline of IVC was not a sudden collapse but a gradual process of de-urbanization beginning around 1900 BCE, accelerating through 1700 BCE, and resulting in the complete abandonment of all major urban centres by 1200 BCE. No single cause explains the entire phenomenon.

Theory 1: Aryan Invasion / Migration (Wheeler, Piggott, Gordon Childe)

• Proposed by Mortimer Wheeler in the 1940s–50s based on: (a) Rigveda's description of Indra as Purandara (destroyer of forts/puras); (b) a group of ~37 skeletons found in the upper levels of Mohenjo-daro in what appeared to be a violent death.
• Now largely discredited: The MJD skeletons are from different time periods, not a single massacre event; they show no sword/battle injuries consistent with military attack; no clear destruction/battle layer at any major IVC site; Rakhigarhi DNA evidence (2019) does not support a massive external invasion replacing the IVC population.

Theory 2: Climate Change and Monsoon Failure (Possehl, Giosan, Petrie)

• A 2012 Yale University/PNAS study (Giosan et al.) using geomorphological and palaeoclimatic data showed that South Asian monsoons weakened significantly around 2100–1900 BCE — precisely when IVC began its decline.
• Reduced rainfall → reduced river flows → crop failures → food insecurity → abandonment of sites that depended on regular flooding for agriculture.
• Eastern sites (Gangetic plain) were less affected — explains why Late Harappan cultures expanded eastward while western/Indus-valley sites were abandoned.
• Currently the most widely accepted primary cause of IVC decline in mainstream archaeology.

Theory 3: Drying of the Saraswati / Ghaggar-Hakra (B.B. Lal, K.S. Valdiya, Possehl)

• The Ghaggar-Hakra river system (identified by many with the Vedic Saraswati) was the most densely settled IVC zone — more sites than the Indus river itself.
• Tectonic activity and/or reduced Himalayan glacial melt caused the Ghaggar-Hakra to dry up around 2000–1900 BCE, depriving hundreds of eastern IVC sites of water and forcing mass migration.
• Explains sudden abandonment of sites like Kalibangan, Banawali. K.S. Valdiya's satellite/geological studies have traced the course of a once-mighty river system that dried up in this period.

Theory 4: Tectonic Activity and Flooding (Robert Raikes, Lambrick)

• At Mohenjo-daro specifically, evidence of repeated flooding is visible in stratigraphic layers — habitation floors were raised repeatedly (up to 10 times) to escape flood levels.
• Raikes and Dales proposed that tectonic uplift downstream dammed the Indus, causing extensive flooding. Explains Mohenjo-daro's decline specifically; less applicable to other sites far from the Indus.

Theory 5: Trade Collapse

• The Akkadian Empire (Mesopotamia) collapsed around 2200–2150 BCE (possibly also due to climate change), disrupting the long-distance trade network that IVC depended on.
• Loss of trade revenue undermined the IVC urban economy; Sumerian records show Meluhha trade declining after c. 2000 BCE — corroborating evidence.

Consensus View: Gradual Multi-Causal Decline with Eastward Migration

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