Initial or mutual trust (the type of trust that makes us, irrationally, trust strangers) then enabled the complex planning that allowed man to transition from a tribe of hunter-gatherers whose fate depended on external factors to an agricultural society where complex, planned outcomes could be put into motion.
David Amerland, The Tribe That Discovered Trust: How Trust Is Created, Propagated, Lost and Regained in Commercial Interactions
civilization, culture, trust