Simon Worrall, "Building walls may have allowed civilization to flourish
," National Geographic
(October 5, 2018), an interview with David Frye, author of Walls: A History of Civilization in Blood and Brick
(New York: Scribner, 2018)
Let's go back in time to the first walls. Who built them and why?
The first walls were city walls and they originated with the very first cities, like Jericho, the city of the Bible, which was first constructed sometime in the tenth millennium B.C., as many as 12,000 years ago. It was a walled city and, subsequently, nearly all cities in the ancient world were walled.
The first border walls aren't found until the late 2000s B.C., in Mesopotamia. Security is why they were built. There were two different lifestyles developing: a lifestyle of the people I call wallers, who are workers who build things and identify themselves by their civilian occupations. They sought to secure themselves by building structures that would protect them even when they were sleeping at night. Outside the walls, you have a very different sort of society, people inured to the dangers of living in an un-walled world. Non-wallers were peoples we generally refer to historically as barbarians, like the Huns, the Goths, or the Mongols. They were viewed with fear by the wall-builders. And that's what inspired the construction of the early walls.
You write, "No invention in human history played a greater role (than walls) in creating and shaping civilization." Some people might vote for writing or gunpowder. Make your case.
I would make the case that there would be no writing and nothing as complex as gunpowder without first the construction of walls. The ancient human need for security is one of the fundamentals of life and has to be achieved before we can achieve other things. It was walls that gave people the security to sit and think. It's hard to imagine a novel being written in a world in which every man is a warrior. Until a society achieves security, it can't think about anything except the dangers all around it. As a consequence its culture will be limited.