Answer: 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 BCE, 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 BCE, in China by about 1500 BCE and in Central America (what is now Mexico) by about 1200 BCE. Civilizations ultimately developed on every continent except Antarctica. Characteristics of Civilization All civilizations have certain characteristics. These include: (1) large population centers; (2) monumental architecture and unique art styles; (3) shared communication strategies; (4) systems for administering territories; (5) a complex division of labor; and (6) the division of people into social and economic classes. Urban AreasLarge population centers, or urban areas (1), 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 CE. 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. MonumentsAll civilizations work to preserve their legacy by building large monuments and structures (2). 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 CommunicationShared communication (3) 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 mountains. 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 BCE. 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