Graeber’s model is refuted by the existence of pre-fiat currencies, the Wampum, the Chinese copper cowrie, and Bitcoin. Where Bitcoin is a currency but just deflationary like gold. Optimal currencies of course are inflationary or stable [1].

[1] This is a simplification, the real optimal rate of inflation is really -0.8% as shown in the seminal paper The Optimum Quantity of Money.