What are some of the early human behaviors that mark important stages in the development towards civilization

The most important human behavior that marks the development towards civilization is the adoption of agriculture. Without agriculture, civilization in the strict sense of the word, cannot exist.

Once agriculture is established, another importat human behaviour for civilization ensues: the adoption of a sedentary lifestyle. Non-agricultural societies are either nomadic, or semi-nomadic, because they have to roam around a geographic area in search of scarce resources. Agricultural societies are sedentary instead, they can settle in a single place because agriculture produces enough food for them to not need move around.

A final behaviour is the full development of social institutions such as the division of labor, private property, and social hierarchy. While these institutions do exist in non-agricultural societies, they are developed to a much lesser degree.