Your story of the origin of money is one that anthropologists have been trying to debunk for decades, because there's simply no evidence that any group of people have gone through the timeline "self sufficiency--barter--money".
In most money-free societies, you'd simply go to your lentil friend and say, "Hey, I'd like some lentils. Come by any time you want potatoes." (Or more likely, you might let your lentil friend overhear you say to someone else, "Oh, what would I not do for lentils right now?" and the desire for credit is implicit.)
Barter only happens between complete strangers, and only under large doses of suspicion. (For what is barter if not trying to pawn off some worthless junk to a less suspecting person in exchange for something cool? It suffers from a perpetual lemon problem and is a business fraught with threat of violence.)
It's also important to consider separately money as a numeraire (in which capacity it has been around for a long time in e.g. legal codes) and money as a medium of exchange (in which capacity it's primarily been used imperially, to make the feeding of armies more efficient.)
I highly recommend reading about money and value from a historical anthropology perspective. Few things are what they seem in this field.
In most money-free societies, you'd simply go to your lentil friend and say, "Hey, I'd like some lentils. Come by any time you want potatoes." (Or more likely, you might let your lentil friend overhear you say to someone else, "Oh, what would I not do for lentils right now?" and the desire for credit is implicit.)
Barter only happens between complete strangers, and only under large doses of suspicion. (For what is barter if not trying to pawn off some worthless junk to a less suspecting person in exchange for something cool? It suffers from a perpetual lemon problem and is a business fraught with threat of violence.)
It's also important to consider separately money as a numeraire (in which capacity it has been around for a long time in e.g. legal codes) and money as a medium of exchange (in which capacity it's primarily been used imperially, to make the feeding of armies more efficient.)
I highly recommend reading about money and value from a historical anthropology perspective. Few things are what they seem in this field.