One can find precursors of nearly every aspect of the modern social media back in newsgroups from the Usenet era during the 1980s and 1990s, including cat memes. Unix developer Rob Pike even invented role-play trolling in the 1980s on Usenet (mostly manually, but an automated bot was also tried). Back then it was a harmless hoax, and today on the modern web it's now causing massive troubles. [0]

Old-timers like Ken Thompson clearly have understood the nature of a social network since a long time ago.

[0] https://en.wikipedia.org/wiki/Mark_V._Shaney#History