The first direct reference of roman culture and humanity as a general reference to their economy and political structure was inherent in Ambrogio Lorenzetti's  "The Allegory of Good and Bad Government." The series of frescoes was presented for all to see on the walls of the Council Room located in the Palazzo Publico (Public Palace). His works portrayed a strong social message to cities and governments in regards to how they should interact with each other. It offered a strong warning to corrupt governments by creating a plague of destruction on a tyrannical and corrupt government, as well as offering contrast with the vibrant economy and happy culture of a "good" government.

Even though these works encompass the great importance of religion in everyday life, they signify the shift towards anthropocentric styles and beliefs that were starting to prevail in the 1300's. It is also not a coincidence that the frescoes are painted on the wall of what is know as the public place, for all to see. In my opinion Lorenzetti opened the door to future works and inspired them to create expressions in the  human world and move farther away from the theocentric style seen in the gothic era. 

Source:
http://rense.com/general92/alleg.htm
http://www.casasantapia.com/art/ambrogiolorenzetti/goodandbadovernment.htm