The Indus Valley civilization

Indus builders made bricks in the same proportions, 1 : 2 : 4, in cities about 600 kilometres apart.

A civilization found in the 1920s

In 1921 Daya Ram Sahni began excavating at Harappa, beside the Ravi River in Punjab. In 1922 R. D. Banerji started digging at Mohenjo-daro on the Indus in Sindh, about 600 kilometres away in a straight line. The finds at the two sites matched: the same stamp seals, the same weights, the same bricks and pottery. Archaeologists realised they had found one civilization that had been completely forgotten. It is called the Indus or Harappan civilization, after the first site excavated, and most of its cities lie in today’s Pakistan and northwest India.

Phases and dates

Archaeologists usually divide its history into three phases: Early Harappan, about 3300 to 2600 BCE; Mature Harappan, the age of the big cities, about 2600 to 1900 BCE; and Late Harappan, after which the large cities were left behind by about 1300 BCE. The Metropolitan Museum dates its Indus seals to about 2600 to 1900 BCE. Some researchers end the mature phase around 2000 BCE instead. The boundary is partly a matter of definition, because different cities declined at different times.

Planned cities

Mohenjo-daro, Harappa, Dholavira and Lothal share a pattern: a raised, walled area on one side, often called the citadel, and a larger lower town of houses. Main streets run north to south and east to west and meet at right angles. Houses were built of baked brick in standard proportions, with thickness, width and length in a ratio of about 1 : 2 : 4. Many houses had a washing area connected to covered drains that ran along the streets, one of the earliest city drainage systems known anywhere.

At Mohenjo-daro, excavators in 1926 uncovered the Great Bath, a sunken brick tank about 12 by 7 metres with steps at each end, its joints sealed with bitumen to hold water. Nobody knows exactly how it was used. Most scholars suspect a ritual purpose, such as bathing before ceremonies, but no text explains it.

Weights, seals and trade

Indus traders used small cube-shaped stone weights that follow one system across the whole region: the smaller weights double each time (1, 2, 4, 8, 16 and so on), and the larger ones grow in steps of ten or so. Square stamp seals, carved with an animal such as the one-horned "unicorn" bull and a short row of signs, were pressed into clay to mark goods and sealed bundles. Indus seals and carnelian beads have been found in Mesopotamia, and Mesopotamian texts mention a distant land called Meluhha that many scholars identify with the Indus region.

A script nobody can read

Somewhere between 400 and 600 different Indus signs are known, but most inscriptions are very short, often only a few signs on a seal. No bilingual text like the Rosetta Stone has been found, and we do not know which language the signs recorded. The script is therefore still undeciphered, and a few researchers even question whether it was a full writing system rather than a set of symbols.

No grand royal tombs

Unlike Egypt and Mesopotamia, the Indus cities have not produced pyramids, rich royal tombs or palaces covered with a ruler’s victories. How the cities were governed, and by whom, remains an open question. After about 1900 BCE the big cities shrank. There is no sign that Harappa was destroyed by invaders. Most explanations combine slower changes: rivers shifting their courses, a weaker monsoon, and a decline in long-distance trade. People did not vanish; settlements moved east and became smaller farming villages.