During this age, humans got food only from hunting and gathering* The Neolithic Era
The Paleolithic Era
The Stone Age
The Prehistory Age

Ithink it’s bill gates.

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.