Sumer was a contemporary of early Egypt....although it had developed an agricultural tradition earlier than Egypt...It is thought that Sumer [this is a later Aggadian name given to it later in it's history by the invasion and occupation of Hammurabi]...began it's agricultural and irrigation projects about 5,000BCE (although there are arguments of a later date). The dates found at Ur, one of the earliest cities in an early City-state, is 4,000-4,500BCE.
Egypt's earliest dates, as far as cities, are from Nekhen [Greek Hierakonpolis] and are ca.4,000BCE. This date is thought to have been at the time when Nekhen was already a full-blown city with brewry, bakery, temple/shrine and a large urban population....
Late Paleolithic and Neolithic peoples had migrated into both places very early on in prehistory, and as there are more excavations, with earlier dates being found in both places...one can only state [as far as archaeology], that Sumer did trade with early Egypt....[much of what can be found online is outdated by recent discoveries in both Iraq [Sumer] as well as Egypt...this is on-going as more excavations occur]....
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