The earliest precursor of writing (1977)
en.finaly.org
en.finaly.org
For one example of why, consider the earliest depiction of the word for sheep: a circle with a cross. Sheep were one of the largest commodities in Mesopotamian trade, and yet only a handful of tokens matching that crossed-disk shape have ever been discovered. If transactions involving sheep were taking place daily, they should be among the most plentiful of tokens. These token systems are an ingenious human invention, but they should be seen as the precursors to mathematical accounting, not writing.
Not sure of the origin of mesoamerican writing.
Middle eastern writing's origin (motivation) is also unclear.