>Barter involves agreeing on a specific exchange rate

This does not match with any definition that I've seen. Graeber debunks a parable used by Adam Smith and economists used to explain why money is more efficient than barter. The problem is that the central thesis of the parable still stands: trade is more efficient with through a medium of exchange.

Wikipedia opens that

> barter, for example, features immediate reciprocal exchange

Reciprocality requires figuring out how many chickens a Ford Taurus is, i.e. the exchange rate.

Graeber's examples of early debt are reciprocal. Otherwise, there would be no need to record them. Sure, it's not as transactional as money is, but it's a transaction nonetheless. I'll admit it's not immediate, but I don't think that's a particularly meaningful distinction. It's not particularly difficult to trust a farmer within your community when they say they'll offer you grain in the future during harvest season. They'd risk ostracization if they break their promise, which is close to a death sentence in that era.

I remember several examples of qualitative generosity and not quantitative reciprocity, but it was a while since I read the book, so I accept that I might remember incorrectly.