I think you misunderstood his point- in a system without money, you can directly barter (ie I give you an apple for your your orange), or adopt a ‘credit’ based system (ie I give you an apple today, and when I need a favor I’ll ask you for one - like the Godfather, for example).

What the book ‘Debt’ discusses is that credit based systems were the norm, not bartering.

In fact, iirc even bats have been shown to keep track of who shares food with them, and to share excess food with a less lucky partner, provided that partner continues to reciprocate.