"how did humans organise themselves in mass-cooperation networks [a.k.a. Socioeconomic systems] when they lacked the biological instincts necessary to sustain such networks? The short answer is that humans created imagined orders and devised scripts. These two inventions filled the gaps left by our biological inheritance."
Turns out these scripts tend to invoke a divine decree as a warrant for legitimacy, as we know. But it's very doubtful that these hierarchical orders were planned and hammered out by Hammurabi and co., as Harari insinuates, with many times the cunning of a modern PR consultancy or even fully consciously. Who is going to accept and carry out his social role no matter how lowly just because some clever storytellers concocted and disseminated the very story to organize hundreds of thousands into stable economic networks? Narratives probably emerged and evolved along with mass cooperation networks. The numinousness bestowed via divine blessing on the experience of the revelation of "justice" (which differs based on the socioeconomic organization in play) is a strong hint that there is indeed an instinctive aspect to human narratives supporting the social order. We don't get it yet because we're too focussed on discrete entities as ontically "fundamental" (perhaps part and parcel of the individualist script in play today that has supported the socioeconomic order known as capitalism.)
Narratives can be concocted and are influential but the notion that the powerful can manage to manipulate the organization of whole civilizations by consciously concocting tales of divinely legitimated justice is utterly simplistic. Nevertheless this and similar explanations are advanced indirectly in works like Ian Morris's Why the West Rules for Now. One thing the historical supposition of a transcendental source of justice has left even non religious investigators today is the sense that we are above nature and that our various versions of narratives of justice are not instinctually rooted.