Introduction

The Indus River Valley is important to ancient human history. It is located in the Middle East. Today, we know the areas as the countries India and Pakistan.

Starting in the 1800s, archaeologists began searching here. Many artifacts were found. We learned about people who lived here. Still, we do not understand their writing. So, we try to understand their way of life based on other evidence. Their art and objects left behind are some examples. More recently, genes and DNA have been studied. These are the body’s instructions on how to grow and work. Genes are passed from parent to child.

We do know that the major cities of this society were well organized. They had advanced technology. These farming communities shared religious or spiritual beliefs. Language and trade networks were shared too. The society appears to have declined around 1700 BCE. Historians and archaeologists continue to debate reasons why.

Harappa and Mohenjo-daro (c. 3500—1700 BCE)

Two large cities have been found from the Indus River Valley society. They are Harappa and Mohenjo-daro. Both are located where Pakistan is today. The cities are about 400 miles apart. Still, they are similar in interesting ways. Some parts are built on mounds. Being high up protected them from flooding. It could likely help defend from attackers, too. The streets were laid out in a grid. Special well systems delivered fresh water to people. A drainage system could dump waste outside of the city. Neither city had a central palace or temple. It’s possible this society was run by several wealthy families rather than a central ruler. Producing and trading goods seemed to be their main focus. Trade networks were broad. Goods traveled back and forth from the Indus cities. They even went places further out, such as Mesopotamia.

About 40,000 to 60,000 people lived in each city. With numbers that high, farming was needed to feed everyone. These culturally connected cities covered a large area. It was bigger than modern city-states of Mesopotamia and the society that had formed in Egypt.

Both cities began as small farming communities. They also produced handmade items. Beads and metal work are examples. The cities grew over time to become important trading areas. As their wealth grew, so did their size. More mounds were added. Some new buildings were for producing goods. Other mounds had homes. They put in roads that allowed wheeled carts to move through the city for trade. Some expanded to two-lane roads. Even more traffic could get through this way. (Yes, sadly, there was traffic back then, too.)

Writing, Trade, and Spiritual Beliefs

The most significant forms of writing that we have of these societies also involve trade. Thousands of stamp seals¹ have been found. They had a variety of animals and decorations on them. The writing on these seals has yet to be translated. Still some images show up more than others. About two of every three seals found show a unicorn. Other seals with real animals have also been uncovered. Archaeologists believe that the animal symbols stood for a rich family or person. These would have been used to mark their goods for trading purposes. It’s possible that some of the seals were important for religion. For example, look at the seated male figure below with horns on his head. He appears often and may be a god, but we do not know for sure.

The same theory holds for the female figure shown below at right. She is shown strangling two tigers. Archaeologists, however, haven’t found any proof of a main temple for the worship of gods. Maybe religious beliefs were more personal for these communities. The symbols and images appear similar to those of other nearby societies. The image of a god-like figure strangling wild beasts such as tigers can also be found in the Mesopotamian Epic story of Gilgamesh.² This could show that ideas got shared through trade networks.

Researchers have also found pottery with some of the same markings as those on seals. Such signs could suggest another connection between the seals and rich families involved in trade. Also, small tablets with the Indus script and symbols have been found. Language scholars believe that these could be a numbering system. Interestingly, many of the tablets were broken in half. They may have been business contracts: each party received half of the tablet as proof of the deal. It’s like a receipt on a rock.

Trade networks certainly peaked between 2600 and 1900 BCE. Very many items from different societies of that period have been found in the region. The beautiful blue stone called Lapis lazuli was one. Metals such as gold, silver, and tin have all turned up in Harappa. These would have traveled from areas such as modern-day Afghanistan and Iran. Harappan pottery, seals, and weights have been found in many modern societies such as those in Mesopotamia. From about 1900 BCE, some of the main cities experienced changes in population. Still, historians still don’t know why these changes happened. Or many don’t agree why.

Decline? Invasion? Transition?

The people of Mohenjo-daro left about the same time Harappa declined. According to environmental historians and geographers, the river that supplied fresh water to Mohenjo-daro changed course. That would have been a good reason to leave town. Archaeologists have noticed less care for drains and roads in Harappa from about 1900 BCE. They believe that this could be because resources were spread too thin. Overpopulation, climate change, and less trade were likely to blame.

For many years, experts wondered if Indo-Europeans invaded the Indus River Valley region. We do have evidence of a group of Indo-Europeans from the Eurasian steppes, or grasslands, moving into the area. They brought their language, knowledge, and horses and chariots, which were pretty high-tech at the time. Genetic studies³ were done recently. They show that, rather than invading, the Indo-Europeans migrated and mixed in with the native people of the Indus Valley region. But they likely did not cause the population to fall or change.

Today, most experts believe that people left some cities because of climate change, moving tectonic plates, and a change in the course of rivers. Tectonic plates are large interlocking slabs on Earth’s hard outer layer, called the crust. The plates fit together like puzzle pieces, right beneath our feet.

The Indus River Valley communities did not die out or fall apart. Populations migrated in some areas and trade declined. Still, the culture lived on and transformed for many more years.

1 Stamp seals were carvings made in stone. They were then used to stamp (make impressions) in soft clay that was then hardened.
2 According to most scholars, the Epic of Gilgamesh is the oldest surviving work of literature (2100 BCE).
3 Note that these genetic studies are often debated. Additional data is most certainly needed before making conclusions about these ancient migrations.