Answer:
Sequentially
Step-by-step explanation:
Concurrency is about independent events executed in random order with the same outcome. Sequential signifies dependence on execution step-by-step for desired results.
Civilizations across the world developed first from hunter-gatherers and then to permanent agricultural societies. Then this allowed specialization of labor which then allowed trading which then created merchants and a labor hierarchy. All these aspects build upon each other in order. You can't have specialization of labor without agriculture being sustained (food surplus).
Moreover, trade allowed the trading of ideas and foods among civilizations that allowed them to better develop and survive.