How did Mesopotamian writing develop from pictures into wedge-shaped signs?

The development of Mesopotamian writing from pictographs to wedge-shaped signs, known as cuneiform, was a gradual process driven by the practical limitations of writing on clay.12

Initially, the Sumerians used pictographic tablets to record commodities, where drawings represented concrete objects. As urbanization increased, these symbols became more conventionalized and abstract. Because clay is not well-suited for drawing curved lines, scribes shifted toward using straight lines.123

The transition to the characteristic "wedge" shape occurred when writers replaced pointed styluses with blunt, slanted ones. By pressing the edge of the stylus into the soft clay, the writer created triangular impressions. Over time, these strokes became the standard, and the script evolved from a system of realistic pictures into a conventionalized, word-syllabic script. This evolution also involved rotating the signs on their sides, fixing the writing direction from left to right.231