For an example of money showing up in Barter systems look at diablo 2's use of stone of Jordon's as a proxy for money.

It can't prove it any better than than anything else can bridge the is-ought gap. I agree that markets can't exist without money, but I think historical evidence suggests that they will create money in order to exist. Almost every society in human history has developed a monetary system; either one based around a commodity as simple as camels, bullion or sea shells, or backed by fiat.

Well, the same author from the link I gave happens to have also written a book on that very topic that you might find interesting:

https://en.wikipedia.org/wiki/Debt:_The_First_5000_Years

I'll check it out. Thank you.