I would say that the real killer invention of humans, compared to other apes, is the way to overcome the Dunbar number and organize very large coordinated group

I would say that the real killer invention of humans, compared to other apes, is the way to overcome the Dunbar number and organize very large coordinated groups. The rise of agriculture in Mesopotamia enabled by it predates writing systems, and the first cuneiform records are purely numerical, for asset tracking. Huge armies, like these of Alexander or Genghis Khan, consisted of mostly illiterate warriors. I'd argue that the invention of the virtual hierarchies, when a peasant submits to a king who he never saw in person, eventually led to the invention of gods, and later a supreme "creator of the universe" figure. That allowed for even more complex cooperative social structures, still across mostly illiterate populations, even though holy scriptures play a central role in such religions.