A nomadic, Indo-European tribe called the Aryans suddenly overwhelmed and conquered the Indus Valley Civilization.
Indus Valley Civilization, located in modern-day India and Pakistan, began to
decline around 1800 BCE. The civilization eventually disappeared
along with its two great cities, Mohenjo-daro and Harappa. Harappa lends its name
to the Indus Valley people because it was the civilization’s first city to be
discovered by modern archaeologists.
evidence indicates that trade with Mesopotamia, located largely in modern Iraq, seemed
to have ended. The advanced drainage system and baths of the great cities were
built over or blocked. Writing began to disappear and the standardized weights
and measures used for trade and taxation fell out of use.
have put forth differing theories to explain the disappearance of the Harappans,
including an Aryan Invasion and climate change marked by overwhelming monsoons.
Invasion Theory (c. 1800-1500 BC)
Valley Civilization may have met its demise due to invasion. According to one
theory by British archaeologist Mortimer Wheeler, a nomadic, Indo-European
tribe, called the Aryans, suddenly overwhelmed and conquered the Indus River
who was Director-General of the Archaeological Survey of India from 1944 to
1948, posited that many unburied corpses found in the top levels of the Mohenjo-daro
archaeological site were victims of war. The theory suggested that by using
horses and more advanced weapons against the peaceful Harappan people, the
Aryans may have easily defeated them.
after Wheeler proposed his theory, other scholars dismissed it by explaining
that the skeletons were not victims of invasion massacres, but rather the
remains of hasty burials. Wheeler himself eventually admitted that the theory
could not be proven and the skeletons indicated only a final phase of human
occupation, with the decay of the city structures likely a result of it becoming
opponents of the invasion theory went so far as to state that adherents to the idea
put forth in the 1940s were subtly justifying the British government’s policy
of intrusion into, and subsequent colonial rule over, India.
elements of the Indus Civilization are found in later cultures, suggesting the
civilization did not disappear suddenly due to an invasion. Many scholars came
to believe in an Indo-Aryan Migration theory stating that the Harappan culture
was assimilated during a migration of the Aryan people into northwest India.
scholarship suggests the collapse of Harappan society resulted from climate
change. Some experts believe the drying of the Saraswati River, which began
around 1900 BCE, was the main cause for climate change, while others conclude
that a great flood struck the area.
major environmental change, such as deforestation, flooding or droughts due to
a river changing course, could have had disastrous effects on Harappan society, such
as crop failures, starvation, and disease. Skeletal evidence suggests many
people died from malaria, which is most often spread by mosquitoes. This also
would have caused a breakdown in the economy and civic order within the urban
Another disastrous change in the Harappan climate might have been
eastward-moving monsoons, or winds that bring heavy rains. Monsoons can be both
helpful and detrimental to a climate, depending on whether they support or
destroy vegetation and agriculture. The monsoons that came to the Indus River
Valley aided the growth of agricultural surpluses, which supported the
development of cities, such as Harappa. The population came to rely on seasonal
monsoons rather than irrigation, and as the monsoons
shifted eastward, the water supply would have dried up.
1800 BCE, the Indus Valley climate grew cooler and drier, and a tectonic event
may have diverted the Ghaggar Hakra river system toward the Ganges Plain. The Harappans may have migrated
toward the Ganges basin in the east, where they established villages
and isolated farms.
These small communities could not produce the same agricultural
surpluses to support large cities. With the reduced production of goods, there
was a decline in trade with Egypt and Mesopotamia. By around 1700 BCE, most of
the Indus Valley Civilization cities had been abandoned.