20,000 B.C. to 2,500 B.C.
The invention of arithmetic provides a way to abstractly compute numbers of objects.
The Lascaux cave paintings record some of the first known narrative constructions.
The Babylonian census begins the practice of systematically counting and recording people.
Written language emerges [pictured: an early cuneiform tablet], providing a systematic way to record and transmit knowledge.
The first known calendar system is established in Mesopotamia, creating a 360-day year.
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