Wondering if my paradigm that people are territorial was correct, I did a web search to find the definition of territorial. Found an interesting article by Desmond Morris regarding territorial behavior. Glancing at other search result blurbs about animals marking their territory, I already had my answer before reading Morris' article. Humans are animals, so yes, it is true, we are territorial.
It has been too long since I worked at a job to remember exact incidents that lead me to define co-workers or people in general as being territorial. Except perhaps in lunch or break rooms, where certain people sat in the same place daily, and lord help the newcomer who unwittingly sat on their chair or at their place at the table.
Who's the boss?
When I am at my neighbor Phil's church to help with the Food Bank, I notice the same kind of territorial behavior.