- The Chalcolithic (also called the Copper Age and Eneolithic) is an archaeological period characterized by the increasing use of smelted copper. It follows the Neolithic and precedes the Bronze Age. It occurs at different periods in different areas, and is absent in some parts of the world, such as Russia. Stone tools were still predominantly used during this period.
- Sumer (Wikipedia)
Sumer (/ˈsuːmər/) is the earliest known civilization in the historical region of southern Mesopotamia (now south-central Iraq), emerging during the Chalcolithic and early Bronze Ages between the sixth and fifth millennium BC. Like nearby Elam, it is one of the cradles of civilization, along with Egypt, the Indus Valley, China, Caral-Supe, and Mesoamerica. Living along the valleys of the Tigris and Euphrates rivers, Sumerian farmers grew an abundance of grain and other crops, a surplus which enabled them to form urban settlements. The world’s earliest known texts come from the Sumerian cities of Uruk and Jemdet Nasr, and date to between c. 3350 – c. 2500 BC, following a period of proto-writing c. 4000 – c. 2500 BC.