Short answers, pulled from the story.
The first documented fandom formed in 1870 when a group of women in England began writing letters about Jane Austen novels. These Janeites shared deep knowledge of minor details and created early forms of fan fiction.
Science fiction fandom began holding annual conventions starting in 1939 with the World Science Fiction Convention running every year since then. This tradition established its own language called fanspeak and included members like Marion Zimmer Bradley, Poul Anderson, Randall Garrett, David D. Friedman, and Robert Asprin.
Media fandom split from science fiction fandom in the early 1970s by focusing on relationships between characters in TV shows like Star Trek and The Man from U.N.C.L.E.. Fans created fan art and fan fiction at a time when most science fiction fans only discussed criticism.
Anime and manga fandom began in Japan during the 1970s before spreading to America as an offshoot of science fiction fandom. Before anime was licensed in the U.S., fans leaked copies of movies and subtitled them to share with friends, marking the start of fansubs.
The furry fandom originated at a science fiction convention in 1980 after a drawing of Steve Gallacci's Albedo Anthropomorphics sparked discussion about anthropomorphic characters.