The name Mesopotamia (meaning "the land between the rivers") refers to the geographic region which lies near the Tigris and Euphrates Rivers and not to any particular civilization. In fact, over the course of several millennia, many civilizations developed, collapsed, and were replaced in this fertile region. The land of Mesopotamia is made fertile by the irregular and often violent flooding of the Tigris and Euphrates Rivers. While these floods aided agricultural endeavors by adding rich silt to the soil every year, it took a tremendous amount of human labor to successfully irrigate the land and to protect the young plants from the surging flood waters. Given the combination of fertile soil and the need for organized human labor, perhaps it is not surprising that the first civilization developed in Mesopotamia. The origins of civilization can be traced to a group of people living in southern Mesopotamia called the Sumerians. By c.3500 BCE, the Sumerians had developed many of the features that characterized subsequent civilizations. Towns grew to be cities, an early form of pictographic writing was used, metal working had begun, and temples were built on a monumental scale. Generally speaking, however, true civilization is said to have begun around 3100 BCE with the development of cuneiform writing. Cuneiform was a system of writing established by the Sumerians which required the use of a stylus in order to make wedge-shaped marks on wet clay tablets, once the tablets were dry they could by stored, transported, etc. After its development, cuneiform became the dominant system of writing in Mesopotamia for over 2000 years. Even after Sumerian became extinct as a spoken language, many other Near Eastern cultures continued to write using cuneiform. As a result of its extensive use of several centuries, many cuneiform tablets have survived. These tablets provide historians with the opportunity to glimpse the culture of the ancient Mesopotamian civilizations.