> We are terribly preoccupied with tool use and physical artefacts as a defining factor of intelligence

In the context of civilisation, intelligence isn’t enough. Nomadic tribes are sapient, intelligent and have rich cultures, but they aren’t strictly civilisations.

The urban distinction is important because of economies of scale: pastoral societies are energy constrained. That doesn’t make them less interesting, again strictly speaking, personally it sort of does, but it does make them less powerful.

Within the Silurian context, the urban distinction is almost demanding: if humans stopped at Neolithic pastoralism, there is a good chance all evidence of our tool use would have disappeared within a few millennia, let alone millions of years.