Hadean
The Hadean () is a geologic eon of the Earth pre-dating the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the ICS, 4 billion years ago. , the ICS describes its status as ""informal"". Geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth. W. Brian Harland later coined an almost synonymous term, the "Priscoan period", from "priscus", the Latin word for "ancient". Other, older texts simply refer to the eon as the Pre-Archean.
Early Dynastic Period (Mesopotamia)
The Early Dynastic period (abbreviated ED period or ED) is an archaeological culture in Mesopotamia (modern-day Iraq) that is generally dated to c. 2900–2350 BC and was preceded by the Uruk and Jemdet Nasr periods. It saw the invention of writing and the formation of the first cities and states. The ED itself was characterized by the existence of multiple city-states: small states with a relatively simple structure that developed and solidified over time. This development ultimately led to the unification of much of Mesopotamia under the rule of Sargon, the first monarch of the Akkadian Empire. Despite this political fragmentation, the ED city-states shared a relatively homogeneous material culture. Sumerian cities such as Uruk, Ur, Lagash, Umma, and Nippur located in Lower Mesopotamia were very powerful and influential. To the north and west stretched states centered on cities such as Kish, Mari, Nagar, and Ebla.