The Indus Valley civilisation flourished in what is now Pakistan and north-west India roughly between 2600 and 1900 BCE, making it contemporary with ancient Egypt and Mesopotamia. Its planned cities, standardised weights, and sophisticated drainage systems suggest a highly organised society — yet we still cannot read its script.
What was the Indus Valley civilisation?
The Indus Valley civilisation — also called the Harappan civilisation, after the first major site to be excavated — was one of the world's earliest urban cultures. At its height, between about 2600 and 1900 BCE, it covered an area of roughly 1.25 million square kilometres across present-day Pakistan, north-west India, and eastern Afghanistan. This made it the largest of the three ancient civilisations that developed simultaneously in the Bronze Age, alongside Mesopotamia (modern Iraq) and ancient Egypt.
The civilisation was rediscovered only in the 1920s, when British and Indian archaeologists began excavating at Harappa in Punjab (1921) and Mohenjo-daro in Sindh (1922). Before those excavations, the existence of such a sophisticated Bronze Age civilisation in South Asia was unknown to modern scholarship. The Indus Valley civilisation is therefore a powerful example of how much of human history remains buried and only partially understood.
What have archaeologists found at the main sites?
Mohenjo-daro (meaning "mound of the dead men" in Sindhi) is the best-excavated site and provides the clearest picture of Indus Valley urban life. Several features of the site are remarkable by any standard of the ancient world:
Urban planning. Mohenjo-daro was laid out on a deliberate grid plan, with wide main streets and narrower side lanes. This level of advance planning implies a civic authority capable of organising construction on a large scale before a single house was built — something with no parallel in the ancient Near East at the same date.
Drainage systems. Every house in Mohenjo-daro was connected to a covered brick drain — a sewer system. Waste water flowed from individual houses into street drains and thence into larger main drains. This level of sanitary infrastructure was not matched in Europe until the Roman period, over two thousand years later.
The Great Bath. A large public bath (approximately 12 metres by 7 metres, 2.4 metres deep) lined with bitumen waterproofing was excavated at Mohenjo-daro. Its exact purpose is unknown: some archaeologists suggest it was used for ritual purification; others propose it was simply a public bathing facility. The uncertainty is a useful reminder of how limited our interpretive framework is.
Standardised weights. Identical sets of stone weights have been found across multiple Indus Valley sites, implying a system of standardised measurement used for trade — but administered by whom, and how, is unknown.
| Feature | What it tells us | What remains uncertain |
|---|---|---|
| Grid-plan streets | Central planning authority existed | Who held power — no obvious palace or temple found |
| Covered drains | Advanced urban sanitation | Whether this was civic rule or shared practice |
| Standardised weights | Inter-city trade or regulation | What governing body enforced standards |
| Great Bath | Possibly ritual, possibly practical | Its exact function is unknown |
| Absence of weapons | Relatively peaceful society, perhaps | Or weapons were of perishable materials |
Where else did the Indus civilisation extend?
Mohenjo-daro and Harappa are the two largest sites, but the civilisation was far more extensive. Archaeologists have now identified over a thousand Indus Valley sites across a vast territory. Dholavira, in present-day Gujarat (India), is the best-preserved example of a medium-sized Indus city and features a large public water reservoir — evidence of sophisticated water management in a semi-arid environment. Lothal, also in Gujarat, contains what is believed to be the world's earliest known dock, suggesting the civilisation engaged in maritime trade.
Why can't historians read the Indus script?
The Indus Valley civilisation left behind a writing system of approximately 400 to 600 distinct signs, found on stamp seals, pottery, and small carved objects. Despite decades of attempts, no scholar has successfully deciphered it. The reason is the absence of a bilingual text — no Indus-language equivalent of the Rosetta Stone has ever been found. Without a text written in both the Indus script and a known language, scholars cannot establish what sounds or words the signs represent.
This means that unlike Mesopotamia or Egypt — where we can read thousands of administrative records, religious texts, and personal letters — we have no direct written evidence of what Indus Valley people believed, how they governed themselves, what language they spoke, or what they called their own civilisation. Almost everything historians say about Indus Valley religion, politics, and social structure is inference from physical evidence.
How did the Indus Valley civilisation end?
Around 1900 BCE, the major cities of the Indus Valley began to decline: populations fell, the standardised material culture (uniform weights, similar brick sizes, consistent pottery styles) broke down, and the great cities were gradually abandoned. The reasons for this collapse are debated:
- Climate change: Evidence from geological sediment cores suggests that the summer monsoon weakened significantly around 2000 BCE, reducing rainfall and making river-fed agriculture less reliable.
- River course changes: The Ghaggar-Hakra river (possibly the ancient Sarasvati) that supported many eastern Indus Valley sites may have changed course or dried up during this period.
- Migration: Population appears to have moved eastward towards the Ganges plain as the north-west became drier.
- Aryan migration: An older theory proposed that the cities were destroyed by Indo-Aryan migrants or invaders from the north-west, but this is now rejected by most archaeologists, who find no evidence of large-scale violent destruction at most sites.
Frequently asked questions
Was the Indus Valley civilisation discovered by archaeologists from South Asia or from outside?
Both. The first excavations at Harappa (1921) and Mohenjo-daro (1922) were conducted under the auspices of the British-run Archaeological Survey of India. The lead archaeologists were John Marshall (British, Director-General of the ASI) and his colleagues including Daya Ram Sahni and Rakhal Das Banerji — both Indian scholars who made foundational contributions to the discovery. Post-independence, Indian and Pakistani archaeologists have led or co-led the major excavation programmes. The question of who "owns" this discovery and how it features in modern Indian and Pakistani national identities is an active part of contemporary debate.
What is the relationship between the Indus Valley civilisation and modern South Asia?
The connection between the Indus civilisation and the peoples of modern South Asia is an area of active research and sometimes politically charged debate. Genetic studies published from around 2019 onwards suggest that the people of the Indus Valley were related to but distinct from modern South Asians, who also carry the genetic legacy of later migrations into the subcontinent. The Indus civilisation's cultural legacy is less clear: while some scholars identify elements of later South Asian religious practice (such as ritual bathing) that may trace to Indus Valley origins, direct cultural continuity is difficult to establish given the gap of several centuries between the end of the Harappan phase and the development of early Vedic culture.
Why are there no grand temples or palaces at Indus Valley sites?
This is one of the most intriguing puzzles of Indus Valley archaeology. In Egypt and Mesopotamia, large temples and royal palaces are the most prominent architectural features of urban sites. At Mohenjo-daro and Harappa, no building has been definitively identified as a royal palace, temple, or royal tomb. This might mean that Indus Valley society was organised differently — perhaps power was more diffuse, held by merchant councils or civic guilds rather than a single ruler or priestly class. Or it might mean that the relevant buildings have not yet been excavated, or that their functions have been misidentified. The absence of evidence is not evidence of absence.
What materials did Indus Valley people use?
Indus Valley artisans worked in a wide range of materials: baked brick (notably standardised in size across the civilisation), bronze and copper for tools and ornaments, terracotta for pottery and figurines, semi-precious stones (including carnelian, lapis lazuli, and steatite) for jewellery and carved seals, and shell and bone. The famous carved stone seals — small stamp seals featuring animals such as unicorns (animals with a single horn, identity disputed), bulls, and elephants alongside Indus script — are among the most recognisable artefacts of the civilisation and were probably used to mark trade goods or ownership.
Professor Harari can help you think through what the archaeological evidence for the Indus Valley actually proves and what it leaves open — a perfect training ground for the kind of source thinking that earns top marks in history. Visit aitutors.me.