Throughout your life, your communities and networks have changed. When you were a baby, you only knew a few people—maybe parents or siblings. As you grow up, you meet people in school or in your neighborhood. But over time, your networks grew to include people farther away—maybe some you met through social media, people who listened to the same music or played the same games as you. Your sense of community developed as you made friends who lived in other parts of town or even other cities or countries. But networks and communities don’t always expand. Sometimes, networks can shrink—maybe as your family moves houses or you lose touch with people.

We can see these same basic patterns throughout human history. Our foraging ancestors lived in family groups in communities of fewer than 250 people. We think this because evidence suggests that’s the biggest a group can get without laws or writing. These family groups met and traded with their neighbors. While networks grew as resources moved long distances, community sizes stayed the same. The growth of the city and the state changed all those things, at least a bit. A city could be a community of thousands—even tens of thousands—of people living under the control of a government. The government sets laws and develops social systems that determine how people act towards each other. Cities and states both supported trade, first in local networks and later across longer distances, although this trade probably remained limited to a few luxury or durable goods.

In this unit, we look at how very large states—called empires—and portable belief systems began to develop and spread. Both empires and portable belief systems represented another evolution of growth for communities and networks, at least for some. Before we talk about how and why that happened, remember: just like the shift from foraging to farming, the growth of communities and networks didn’t happen for everyone at the same time or at the same rate in every place. And sometimes, even if just temporarily, they shrank. Still, this period experienced an overall trend of growth. Let’s discuss how that expansion happened.

The development of portable belief systems

First, let’s talk about portable belief systems—or more simply, religions.

Today, our world has vast communities of people who belong to the same faith. Major religions include Hinduism, Buddhism, Christianity, Judaism and Islam, among many others. While some belief systems are very local, others stretch across continents and millions of followers. Within these communities, there may be disagreements and differences. However, each group is still bound together by a set of common beliefs, practices and understandings about ways one should act in the world.

Most belief systems early in this era were connected to a location or a group of people. People associated their gods or spirits as attached to sites like rivers and mountains. Or gods lived within a single shrine or temple. But about 3,000 years ago, some people began to think of their gods as universal, meaning they could communicate with followers anywhere. Everyone, regardless of location, could become part of their religious community. These beliefs in universal gods allowed people to create vast networks based on religion. So even while traveling, they might find a like-minded member of their religion to do business with or to reside or worship with. There were huge advantages to joining these universal, portable religions, and many people did so—although, of course, some did not!

But, notably as religions grew, people changed them to fit their way of life. Sometimes people even mixed the new religion with their local beliefs. We’ll see in this unit that the expansion of religions meant a lot of mixing, matching, and adapting—a process called syncretism. This kind of merging and changing happens so often in human history, and not just with religion.

The growth of empires

As religions grew, so did the state. States are political units. More explicitly, they are communities that share a single ruler (or system of rulers) and a unified set of laws, borders, and government institutions. States expand, often by conquering new groups of people who have different laws and governments. However as states grew, they faced the problem of how to make conquered people follow their rules and government. One answer to this question was the empire.

Empires are more than just large states. Empires rule societies that contain many different communities—people in different cities and regions with many religions, ethnicities, and languages. Generally, the empire's solution to these many differences isn’t to make everyone equal. Instead, in an empire, one group of people holds significant power over the others in society.

Around 2400 BCE, Sargon of Akkad created the first empire in Mesopotamia (modern-day Iraq). Since then, many different empires have sprung up. Often, the rulers of an empire let their subjects carry on their own customs and practices, as long as the conquered people paid tribute or taxes. In other cases, empires were very controlling and took advantage of colonized groups to enrich their ruling class.

Empires were a useful solution to the problem of ruling over large and diverse communities. In addition to Mesopotamia, there were others: the vast Persian Empire, the Zhou and Qin dynasties in China, the Mauryan and Gupta empires in South Asia, and the Macedonian Empire of Alexander the Great.

Two great empires of the ancient Afro-Eurasian world were the Roman Empire and Han Dynasty China. These were impressive due to their size, and the number of technologies they invented to rule over great distances. They developed sophisticated roadways and systems of government known as bureaucracies, made up of many officials and departments. Both empires lasted a long time, successfully managing the vast and varied populations under their control.

Importantly, both states existed around the same time. This meant that they also helped create a huge network of trade that extended from Britain to China and Japan. However, they differed from each other in many ways, including how they viewed the role of women in their societies.

Conclusion

Eventually, both empires collapsed. Empires often became politically unstable. This can happen because some populations within them were not treated as well as others. The Roman Empire and Han Dynasty China survived as long as they did because they developed new systems to hold everything together. But just as sometimes happens with people's personal communities and networks, imperial communities and networks sometimes shrink. We’ll explore that theme in the next unit, where we look at the regional aftermath following the collapse of these great world empires.