Civilization describes a complex way of life that came about as people began to develop networks of urban settlements. The earliest civilizations developed between 4000 and 3000 B.C.E., when the rise of agriculture and trade allowed people to have surplus food and economic stability. Many people no longer had to practice farming, allowing a diverse array of professions and interests to flourish in a relatively confined area. Civilizations first appeared in Mesopotamia (what is now Iraq) and later in Egypt. Civilizations thrived in the Indus Valley by about 2500 B.C.E., in China by about 1500 B.C.E. and in Central America (what is now Mexico) by about 1200 B.C.E. Civilizations ultimately developed on every continent except Antarctica.

Characteristics of Civilization

All civilizations have certain characteristics. These include: large population centers; monumental architecture and unique art styles; shared communication strategies; systems for administering territories; a complex division of labor; and the division of people into social and economic classes. The development of urban settlements, cities, is the primary characteristic of a civilization. The other attributes that define civilization are built around urbanization.

Urban Areas

Large population centers, or urban areas, allow civilizations to develop, although people who live outside these urban centers are still part of that region’s civilization. Rural residents of civilizations may include farmers, fishers, and traders, who regularly sell their goods and services to urban residents. The huge urban center of Teotihuacan, in modern-day Mexico, for example, had as many as 200,000 residents between 300 and 600 C.E.

The development of the Teotihuacano civilization was made possible in part by the rich agricultural land surrounding the city. As land was cultivated, fewer farmers could supply more food staples, such as corn and beans, to more people. Trade also played a part in Teotihuacan’s urban development. Much of the wealth and power of Teotihuacan was due to excavating and trading the rich deposits of obsidian around the city. Obsidian is a hard volcanic rock that was highly valued as a cutting tool. Teotihuacano merchants traded (exported) obsidian to surrounding cultures in exchange for goods and services imported to Teotihuacano settlements.

Monuments

All civilizations work to preserve their legacy by building large monuments and structures. This is as true today as it was thousands of years ago. For example, the ancient monuments at Great Zimbabwe are still consistently used as a symbol of political power in the modern nation of Zimbabwe. Great Zimbabwe, constructed between 1100 and 1450, describes the ruins of the capital of the Kingdom of Zimbabwe. At its peak, Great Zimbabwe was inhabited by more than 10,000 people and was part of a trading network that extended from the Maghreb, through the eastern coast of Africa, and as far east as India and China.

Great Zimbabwe is a testament to the sophistication and ingenuity of ancestors of the local Shona people. Politicians like Robert Mugabe, the president who led Zimbabwe for nearly 40 years in the 20th and 21st centuries, built their entire political identities by associating themselves with the ancient civilization’s monumental architecture. Buildings are not the only monuments that define civilizations. The distinct artistic style of Great Zimbabwe included representations of native animals carved in soapstone. The stylized stone sculptures known as “Zimbabwe Birds”, for example, remain an emblem of Zimbabwe, appearing on the nation’s flag, currency, and coats of arms.

Shared Communication

Shared communication is another element that all civilizations share. Shared communication may include spoken language; alphabets; numeric systems; signs, ideas, and symbols; and illustration and representation. Shared communication allows the infrastructure necessary for technology, trade, cultural exchange, and government to be developed and shared throughout the civilization. The Inca civilization, for example, had no written script that we know of, but its complex khipu system of accounting allowed the government to conduct censuses of its population and production across the vast stretch of the Andes. A khipu is a recording device made of a series of strings knotted in particular patterns and colors.

Written language in particular allows civilizations to record their own history and everyday events—crucial for understanding ancient cultures. The world's oldest known written language is Sumerian, which developed in Mesopotamia around 3100 B.C.E. The most familiar form of early Sumerian writing was called cuneiform, and was made up of different collections of wedge (triangle) shapes. The earliest Sumerian writing was record-keeping. Just like written records of modern civilizations, Sumerian cuneiform kept track of taxes, grocery bills, and laws for things like theft.

Written language was a key part of shared communication during the Islamic Golden Age, which flourished in southern Europe, northern Africa, and western Asia from the seventh to the 13th centuries. So-called “Arabic numerals” and the Arabic language were shared communications that allowed diverse cultures across the Arabic world to contribute the dazzling advances in mathematics, science, technology, and the arts.

Infrastructure and Administration

All civilizations rely on government administration—bureaucracy. Perhaps no civilization better exemplifies this than ancient Rome. The word “civilization” itself comes from the Latin word civis, meaning "citizen." Latin was the language of ancient Rome, whose territory stretched from the Mediterranean basin all the way to parts of Great Britain in the north and the Black Sea to the east. To rule an area that large, the Romans, based in what is now central Italy, needed an effective system of government administration and infrastructure. Romans used a variety of methods to administer their republic and, later, empire.

Engineering, for instance, was a key part of Roman administration. Romans built a network of roads so that communication between far-away territories was as efficient as possible. Roads also made travel by the Roman military much easier. Romans built structures of their civilization everywhere they went: aqueducts supplied freshwater to towns for improved sanitation and hygiene, for example.

Language also played a part in Roman infrastructure. Romans spread the Latin language throughout southern Europe. The so-called "Romance languages" (Spanish, French, Portuguese, Romanian, Catalan, and Italian) are called that because they all developed from the Roman language: Latin. Having a similar language made communication and leadership easier for Rome in its far-flung territories. Roman leaders relied on a series of legal codes for administration. These codes helped structure laws between different parts of Roman territory, as well as between rich and poor, men and women, slave and free. Roman laws included restrictions on marriage, ownership of land, and access to professions such as priesthoods. 

One of Rome’s most lasting contributions to Western Civilization was the establishment of legal culture itself. Roman law was largely public, and jurists created such formalities as legal language and procedure that would define European law for centuries. In fact, “Roman law” describes the legal system used throughout Western Europe through the 18th century.

Finally, Romans used local leaders, as well as Romans, to administer the law in their territories. Residents were more familiar with their own leaders, and more likely to follow their announcements. Israeli leaders worked with Roman authorities in the Roman territory of Palestine, for example, while British leaders often worked with Romans on the island of Great Britain. Some people born in Roman territories eventually became Roman emperors: The emperor Constantine, for instance, was born in what is now Serbia; the emperor Hadrian may have been born in what is now Spain. This interaction reduced conflict between Rome and its territories.

Division of Labor

Civilizations are marked by complex divisions of labor. This means that different people perform specialized tasks. In a purely agricultural society, members of the community are largely self-sufficient, and can provide food, shelter, and clothing for themselves. In a complex civilization, farmers may cultivate one type of crop and depend on other people for other foods, clothing, shelter, and information. Civilizations that depend on trade are specially marked by divisions of labor.

The city of Timbuktu, in what is now Mali, was an important trading center for several African civilizations. Residents of Timbuktu specialized in trading such goods as gold, ivory, or enslaved people. Other residents provided food or shelter for trade caravans traveling on camels from the Sahara. The urban center of Timbuktu was also a center of learning. Its division of labor included not only merchants, but doctors, religious leaders, and artists.

Class Structure

The last element that is key to the development of civilizations is the division of people into classes. This is a complex idea that can be broken down into two parts: income and type of work performed. Changing classes has traditionally been difficult and happens over generations. Classes can mean groups of people divided by their income. This division is sometimes characterized as “economic class.” Modern Western Civilization often divides economic classes into wealthy, middle-class, and poor. In medieval civilizations of Europe, there were fewer economic classes. Kings and queens had enormous amounts of money and land. Serfs, or people who worked the land, had almost nothing. Eventually, a merchant economic class developed.

Class can also refer to the type of work people perform. There are many divisions of social class. Social class is often associated with economic class, but not strictly defined by it. In the ancient civilization of China, there were four major types of social classes. Scholars and political leaders (known as shi) were the most powerful social class. Farmers and agricultural workers (nong) were the next most-powerful group. Artists (gong), who made everything from horseshoes to silk robes, were the next order of social class. At the bottom of the social classes were the merchants and traders, who bought and sold goods and services. Known as shang, these merchants were often much wealthier than the other classes but had a lower social status.

Development of Civilization

Civilizations expand through trade, conflict, and exploration. Usually, all three elements must be present for a civilization to grow and remain stable for a long period of time. The physical and human geography of Southeast Asia allowed these attributes to develop in the Khmer civilization. The Khmer flourished in parts of what are now Cambodia, Thailand, Laos, Vietnam, and Myanmar between 800 and 1400.

Trade

The Khmer maintained vibrant trading relationships throughout East Asia, the Indian subcontinent, and even Europe and Africa through the Silk Road, a collection of both overland and maritime trade routes. The Silk Road linked the spice and silk markets of Asia with the merchants of Europe. Southeast Asia’s extensive network of waterways facilitated trade, with the Khmer capital of Angkor being built on the shores of Southeast Asia’s largest freshwater lake, Tonle Sap. The outflowing Tonle Sap River is a tributary of the mighty Mekong River, which connects Southeast Asia with the Tibetan Plateau in the north and the South China Sea in the south. In addition to material goods, the Khmer civilization facilitated a powerful trade in ideas. In particular, the Khmer were instrumental in spreading the influence of Buddhist and Hindu cultures from the Indian subcontinent to Southeast and East Asia.

Conflict

The primary conflicts of the Khmer civilization were waged with neighboring communities—the Cham, the Vietnamese, and the Thai. The Cham were a collection of kingdoms in what is today central and southern Vietnam, while the ancient Vietnamese influence extended through what is today northern Vietnam. Thai kingdoms such as Sukothai and Ayutthaya flourished in what are now Thailand, Cambodia, and Malaysia. The Khmer civilization was founded on the consistent resistance of political pressure from the Cham and Vietnamese, but it ultimately could not withstand pressure from Thai civilizations. Thousands of Thai peoples migrated from the north (what is now the Yunnan region of China), establishing small kingdoms in the southwest of the Khmer Empire. Eventually, these kingdoms became strong enough to annex Khmer territory, leading to Ayutthaya’s conquest of the Khmer capital of Angkor in 1431.

Exploration and Innovation

The Khmer civilization relied heavily on rice farming, and developed a complex irrigation system to take advantage of the rivers and wetlands that dotted their territory. An efficient series of irrigation canals and reservoirs, called barays, allowed fewer farmers to produce more rice. This, in turn, allowed more people to pursue nonagricultural lifestyles and migrate to great urban areas, such as Angkor. Angkor, the capital of the ancient Khmer civilization, is home to one of the largest most distinctive religious monuments in the world, Angkor Wat.

Angkor Wat was originally constructed as a series of shrines to the Hindu god Vishnu in the early 12th century, although it became a Buddhist temple complex less than a hundred years later. Angkor Wat and its sister complex, Angkor Thom, are beautiful examples of classic Khmer architecture. The towering, stepped pyramid towers of Angkor Wat are called “temple mountains.” The towers are surrounded by open gallery walkways, and the entire structure is enclosed by a wall and square moat. The thousands of square meters of wall space at Angkor Wat and Angkor Thom are decorated by thousands of bas-reliefs and sculptures depicting Hindu stories and characters. The Khmer monument at Angkor Wat helps define the modern nation of Cambodia today. It is the nation’s primary tourist attraction, a World Heritage Site, and even appears on the Cambodian flag.

Fall of Civilizations

Many civilizations have flourished and then failed or fell apart. There are many reasons for this, but many historians point to three patterns in the fall of civilizations: internal change, external pressure, and environmental collapse. The fall of civilizations is never the result of a single event or pattern. Sometimes, civilizations seem to “disappear” entirely.

Internal Change

Population dynamics are the most pervasive forces of internal change to a civilization. A sudden population shift or a shift in demographics may force a civilization’s infrastructure to break down. Populations may grow, due to migration or a period of unusual health. Populations may shrink, due to disease, extreme weather, or other environmental factors. Finally, populations may redefine themselves. As civilizations grow, cities may grow larger and become more culturally distinct from rural, agricultural areas. Large empires may extend across such large regions that languages, cultures, and customs may dilute the identity of the empire’s residents.

Internal changes contributed to the collapse of the Maya civilization, which had thrived in Mesoamerica for more than a thousand years. The “Classic Maya” collapse happened relatively quickly in the 800s. Diseases such as dysentery and lethal hemorrhagic fevers killed and disabled thousands of Mayans. Millions more were forced to relocate from cities to more rural areas. Such huge population shifts reduced the ability of the Maya to communicate, administrate, and unite against outside forces and natural disasters (such as drought).

External Pressure

The clearest example of external pressure on a civilization is foreign invasion or sustained warfare. Protecting a civilization’s borders can be extremely expensive and demand a strong military at the expense of developing or maintaining other aspects of a civilization. External pressure can lead to the relatively abrupt end of a civilization (and, often, the adoption of another). The fall of the Aztec Empire with the arrival of European conquistadores is such an example.

External pressures can also lead to the gradual diminishing of a civilization. The “fall” of what we often think of as Ancient Egypt is a good example of how external pressures can redefine a civilization over hundreds of years. Egypt had faced longstanding, intermittent conflict on its borders, with competing civilizations such as the Nubians (to the south), the Assyrians (in the Middle East), and the Libyans (to the west). Later, Egypt encountered the civilizations of Ancient Greece and Rome, and eventually became part of the Roman Empire. Ancient Egypt also faced external pressures not directly associated with armed conflict. The powerful forces of Christianity and Islam influenced the eradication of both hieroglyphics, the writing system of Ancient Egypt, and its polytheistic religion.

Environmental Collapse

Some anthropologists think that both natural disasters and misuse of the environment contributed to the decline of many civilizations. Natural hazards such as drought, floods, and tsunamis, become natural disasters as they impact civilizations. Drought contributed to the fall of civilizations such as the Maya and the Indus Valley or Harappan civilization.

The Indus Valley Civilization was a Bronze Age civilization in what is now Pakistan, India, and Afghanistan. The Indus Valley Civilization depended on seasonal monsoon rains to supply water for drinking, hygiene, and irrigation. Climate change made monsoons much more unpredictable and seasonal flooding less reliable. Harappans suffered from water-borne diseases and were unable to effectively irrigate their crops. The collapse of Minoan civilization, a major influence on Ancient Greece, is often associated with a catastrophic eruption of the Thera volcano on the island of what is now Santorini. The eruption caused a massive tsunami that reduced the population, trading capabilities, and influence of the Minoans.

Human activity can also strain the environment to the point of a civilization’s collapse. One of several factors contributing to the collapse of the Viking outpost in Greenland, for instance, was the failure of European settlers to adapt to Greenland’s climate and soil. Farming methods that were successful in the rich, loamy soils of Northern Europe were ill-suited to Greenland’s colder, thinner soil and shorter growing seasons. The land could not support the crops necessary to sustain Viking livestock, including goats, cattle, and sheep. In addition, the land itself was harvested for peat, the outpost’s primary construction material. The Vikings in Greenland also faced internal pressures, such as a weak trading system with Europe, and external pressures, such as a hostile relationship with their Inuit neighbors.

‘Lost Civilizations’

History and myth are rich with “lost civilizations,” entire ways of life that seemed to flourish and then disappear from the historical record. The disappearance of the Ancestral Puebloan civilization is one such mystery. Ancestral Puebloan civilization thrived in what is now the Four Corners region of the United States: the states of Utah, Colorado, New Mexico, and Arizona.

Ancestral Puebloan civilization developed around 1200 B.C.E. and thrived for more than a thousand years. Ancestral Puebloan civilization was marked by monumental architecture in the form of apartment-like cliff dwellings and large urban areas known as pueblos. Culturally diverse Ancestral Puebloans were connected by a complex road system, a standard style of religious worship, and a unique art style evidenced by pottery and petroglyphs.

Ancestral Puebloans seem to have abandoned their urban areas around 1300 C.E. The disappearance of this civilization remains a mystery, although most scientists say Ancestral Puebloans engaged in warfare with their Navajo neighbors, internal groups competed for land and resources, and sustained droughts reduced Ancestral Puebloan ability to irrigate crops in the arid Southwest. The Pueblo people never disappeared, of course: Diverse groups developed their own, competing civilizations after the Ancestral Puebloans migrated or fell apart. These groups include the Zuni and Hopi civilizations.