There can never be an exactitude attached to the question concerning the "earliest" civilizations. With that said two early civilizations have left ruins, writings and traces of their early existence. One early civilization formed in the area we now know as Syria and land surrounding it. In a place called Sumer, we have evidence of a people living in a mesopotamian style of civilization dating back to 3500 BC.
The second early civilization is further south in the area we now call Egypt. There in around 3100 BC, are the relics and ruins of an ancient Egyptian type of civilization. The hyper dry climate surrounding this civilization has allowed for the preservation of many writings and temples there. Some in total ruin, other ruins are better preserved.
Other civilizations may qualify as the two "earliest" ones.
India and Chinese
Asia has the majority of the earliest civilizations.
Mesotopamia and Egypt. They were both born near river systems.
The three civilizations commonly referred to as "The Classical Civilizations" are the Mediterranean, Indian, and China Civilizations.
atlantis
Some of the world's earliest civilizations developed in the Fertile Crescent in the Middle East. Some of the civilizations are: Sumer, Mesopotamia, and Akkadian.
They were the Aryans and the Dravidian that made it early Hinduism.
the fertile crescent
Near riversThe earliest civilizations arose in Greece and Italy.
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The Persian civilization The Babylonians
river valleys