[lasagnaphil]

Graeber clearly explained the process of how gold currency appeared in his book (I recommend you to reread Chapter 8: The Axial Age for this). It’s because states needed some convenient medium to provide resources for the military to continue its conquests, and that was precisely what the military was already pillaging from its conquered territory: luxury items made of gold. So the state had to find a way to enforce people to sell other important commodities (such as food and equipment) in exchange for gold, and that made the state to enforce gold coins as a currency in areas near conquests.

You’re right that the social/cultural value associated with those luxury gold collectibles is an important part of the story. But I don’t think you need any other weird evolutionary argument in addition to Graeber’s view to complete the full picture.

[magicsmoke]

The state could already force people under their control to sell commodities to their soldiers for clay tokens. Why switch to gold, a much more difficult resource to obtain and produce coinage with? Was clay suddenly no longer convenient for some handwavey reason because we're now in the Axial Age, despite being used for centuries before? That's the gap in Graebers book that I don't think he covered adequately.

The reason was because now the various city states needed a way to convince people outside their jurisdiction to also provide goods and services for their wars, and those people could not be cowed into using clay. Clay only works within a states jurisdiction because they could punish counterfeits and ensure it's value among subjects as a tax credit to the state. Outside a state's jurisdiction, foreign soldiers have no guarantee that those clay tokens will continue to be a secure store of value. What if the state you were fighting for collapsed tomorrow? Now their tax credits are worthless. Gold, on the other hand, holds it's value because people like shiny things regardless of which king is stamped on it. But because the gold is issued by a state with their tendency for standardization, now your gold trinkets come in nice standardized units instead of a random assortment of jewelry, what gold would have been used for previously.

[lasagnaphil]

I thought these were also already explained in Graeber's book...

A paragraph from Chapter 8:

> Why? The single most important factor would appear to be war. Bullion predominates, above all, in periods of generalized violence. There's a very simple reason for that. Gold and silver coins are distin­ guished from credit arrangements by one spectacular feature: they can be stolen. A debt is, by definition, a record, as well as a relation of trust. Someone accepting gold or silver in exchange for merchandise, on the other hand, need trust nothing more than the accuracy of the scales, the quality of the metal, and the likelihood that someone else will be willing to accept it. In a world where war and the threat of violence are everywhere-and this appears to have been an equally ac­ curate description of Warring States China, Iron Age Greece, and pre­ Mauryan India-there are obvious advantages to making one's trans­ actions simple. This is all the more true when dealing with soldiers. On the one hand, soldiers tend to have access to a great deal of loot, much of which consists of gold and silver, and will always seek a way to trade it for the better things in life. On the other, a heavily armed itinerant soldier is the very definition of a poor credit risk. The econo­ mists' barter scenario might be absurd when applied to transactions between neighbors in the same small rural community, but when deal­ ing with a transaction between the resident of such a community and a passing mercenary, it suddenly begins to make a great deal of sense.

[ethn]

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.