> Before the invention of money there was only direct exchange; I do/give something for/to you and you do/give something for/to me in return.

This is ahistoric. Widespread barter is only really takes place in post-currency societies. Pre-currency societies mostly engaged in reputation or "gift" economies. When I have a surplus, I share with peers, with the understanding that they have done and will do the same in the future. It can be tempting to map that social obligation onto currency debt, but reputation doesn't really behave the same way as currency does. It's not linearly combined (giving someone with no bread a loaf of bread is going to provide you much greater than half as much standing with that person than giving them 2 loaves), its transaction costs are much, much lower (you probably wouldn't pay the village idiot, but if you enjoy listening to his tall tales, you probably think fondly enough of him to help him out in a pinch, or share some extra berries you found, or you might value the fact that your neighbor gave a loaf of bread to the guy with none from the earlier example, but it would be weird to pay him for that indirect, incidentally service), and it's barely portable: maybe your kid might benefit somewhat from your prestige in the community, but unless he lives up to it it doesn't matter if you saved the village by single-handily slaying the lion that was picking off children and livestock. Likewise you can't just hop over to the next village and expect people to help you any more than basic hospitality rules demand.