Short answers, pulled from the story.
Émile Durkheim and Ferdinand Tönnies began laying the theoretical groundwork for what would become social network analysis in the late 1890s. Durkheim provided a non-individualistic explanation of social facts through his work on the division of labor published by F. Alcan in Paris in 1893.
Ferdinand Tönnies distinguished between two types of social groups: Gemeinschaft as personal direct ties linking those who share values, and Gesellschaft as impersonal formal links connecting people instrumentally. His book Community and Society appeared first in Leipzig under Fues's Verlag before being translated into English decades later.
Jacob L. Moreno developed the first sociograms during the 1930s to study interpersonal relationships within small groups like classrooms and workplaces. These visual diagrams mapped connections between individuals using lines and nodes to represent dyadic relationships.
Scale-free networks follow power law distributions where some vertices greatly exceed average connection counts creating hub nodes serving specific functions depending on context. Albert-László Barabási published his Linked book describing how everything connects to everything else through Plum publishing in New York during 2003.
Computer networks combined with social networking software created new mediums for interaction beginning in the late 1990s. Duncan J. Watts, Albert-László Barabási, Peter Bearman, Nicholas A. Christakis, and James H. Fowler developed models applying physics principles to online data traces.