The book (Debt, The First 5,000 Years) goes over this (IIRC it's in the Games with Sex and Death chapter). It says that these kinds of "weird money" examples like stone wheels in Micronesia, where not really used to trade for goods, but more or less to trade in social favors / honor systems.
The early mesopotamian cilivilazations got debt and credit before there was coinage. Farmers bought goods on credit, the debt set in grain for example, to be payed on harvest season. Grain, would be as good as money since that's what you paid your taxes in. The whole region had a sophisticated credit culture and the effects of debt were pervasive. That's why the old testament has provisions against usury, the jubilee, etc.