Parallel cradles of civilization
The timeline lines up several early literate societies that arose largely independently. Sumer in southern Mesopotamia developed cuneiform writing and the first cities by around 3500 to 3000 BCE. Ancient Egypt unified under the early dynasties around 3100 BCE along the Nile. The Indus Valley (Harappan) civilization reached its mature urban phase around 2600 to 1900 BCE, with planned cities like Mohenjo-daro and Harappa.
Further east, China's Shang dynasty is dated to roughly 1600 to 1046 BCE and produced the oracle-bone script. In Mesoamerica, Maya civilization developed later, with its Classic period running from about 250 to 900 CE, well after the Old World cradles.
Why the overlaps matter
Placing these on one axis shows that the rise of writing, cities, and states was not a single event spreading from one place but several broadly parallel developments separated by thousands of kilometres. They differ sharply in date: Sumer and Egypt are roughly contemporaneous in the fourth millennium BCE, while the Maya Classic period belongs to the first millennium CE. The shared trait is the transition to literate, urban, state-level organization rather than a common origin.