By a rough approximation I think this is how we got here. For millions of years humans lived in small groups. Then agriculture came along and larger groups of humans lived together. There were cities and nations. At some point groups organized militaries to defend their new cities and nations. For thousands of years the only large organizations were militaries. Then the industrial revolution came along and larger groups of humans worked together. For hundreds of years corporations grew. Now we have multinational corporations made of knowledge workers spread across the globe.
Communication in a small tribe is straightforward. Everyone in the tribe knows everyone else. Communication happens as needed. Relationships are direct.
How do cities, states, nations, militaries, and multinational corporations communicate? Fractal, often hierarchical, tribes. You know your family, maybe neighborhood, some of them know someone else. Spiraling and unfurling webs of implicit and explicit relationships.
Efficient organizations require some structure to formalize relationships. Formal relationships will codify expectations. Clear expectations will engender trust. Abstraction of trust is the key to scaling relationships across large groups of people.
A hierarchical organization is not necessary. There are other ways to organize a large group. In this curriculum we will only be considering management in hierarchical organizations. Leadership topics should be universal, but your mileage may vary.