Instead of saying that money was used to facilitate trade OR used to pack back debts, why not both?
Given how useful money is, I only imagine that it solved many problems that many civilizations and villages ran into.
Recent research from the Americas adds new questions to
the debate. These investigations suggest that money
independently appeared for different reasons and assumed
different tangible forms in many parts of the world,
starting thousands of years ago.To me it seems like it's almost instantaneous, but you could imagine that there would be a period of time where the 100 shells couldn't be traded, they were there to represent the debt of the bride, which would be paid pack like any debt.