If,on your way to work/school this morning, you saw a bunch of hung-over warriors and bedraggled mages blearily waking up in a shop doorway they were probably just on their way home from the 30th birthday pub crawl they organized for the Massively Multiplayer genre.
On October 20th 1978, Roy Trubshaw of Essex University threw the switch on MUD - the original Multi User Dungeon. This simple game was the first to let users experience a shared virtual world - albeit one depicted purely through text descriptions - but still featured the core elements of the modern MMO - collecting loot, gaining experience and killing the other guy first.
Although the original server is long since buried in a landfill, MUD games are still running on UNIX and VMS boxes in th e depths of the internets.