Superman’s continuity is, and has always been, a fluid affair. Since his first appearance a succession of writers and editors have consistently expanded and enriched Superman’s backstory and mythology to the extent that many of his adventures have been reinterpreted and reinvented multiple times. It starts with Jerry Siegel, Superman’s co-creator and his first writer. His Superman is surprisingly different than the one we read today. He is considerable less powerful, but he is also more over bearing and at times acts more like we’d expect Batman to act. His character quickly evolved under the influence of DC editorial policies and a succession of innovations from the licensed cartoons and radio show to become the more familiar paternal/authoritarian figure.

In the late 1940s Siegel and Joe Shuster lost a court case with DC that left them excluded from the character they had created. About the same time editor Mort Weisinger returned to DC after his wartime national service ended. He worked under DC executive Whitney Ellsworth on the Superman franchise and then assumed full control after Ellsworth moved to the West Coast to liase with the producers of The Adventures of Superman. By that time Superman as a character (Clark Kent, last survivor of Krypton, etc) had been defined and his core supporting cast established (Lois Lane, Perry White & Jimmy Olsen). However, it was Weisinger who presided over the foundation of we would now consider the wider Superman mythology – the Fortress of Solitude, Kandor, the Legion of Superheroes, and almost everything we know about Krypton.

In the early 1960s the evolution of Superman’s mythology was encapsulated into DC’s parallel worlds setting. The Weisinger Superman as chronicled in the ongoing magazines was explained to be the Superman of Earth-One (Superman II) while the earlier Siegel Superman (Superman I) belonged to a parallel world called Earth-Two. The two versions even met each other with the Earth-Two version drawn to look like an older man with streaks of white-hair at his the temples. The parallel world structure allowed writers to invent other possible versions of Superman (e.g. Ultraman from Earth-Three), but none of these were ever the prime Superman – the actual hero whose name was on the magazine’s masthead.

The separation between their adventures is not as clear-cut as you might believe as the Earth-Two Superman is an idealised version of the 1940s Superman where his later chroniclers have cherry picked plot elements to deliberately make him appear distinct from the Earth-One Superman. For example it was retroactively decided that only the Earth-One Superman had ever been Superboy despite the fact that Superboy had first appeared during the time when the Earth-Two Superman was still the primary Superman. This fuzzy overlap even led fan-guru Mark Gruenwald to postulate the existence of Earth-E – a hybrid version of the Earth-One and Earth-Two with its own hybrid Superman.

Weisinger retired in from DC in 1970 just as a new wave of energy swept into the Superman franchise. Most of his core duties were taken over by his friend Julius Schwartz. Under his guidance a group of comic book fans turn professional comic book writers refined Weisinger’s expanded continuity into a cohesive canon. These were the first generation of writers who had actually grown up reading about Superman. Their ranks included Cary Bates and Elliot S Maggin and the legendary E. Nelson Bridwell who became the guardian of Superman’s stricter continuity. Several innovations were introduced during Schwartz’s tenure including Clark Kent becoming a TV reporter and elsewhere at DC Jack Kirby was injecting a huge slew of ideas into the Superman franchise by tying it to his own Fourth World stories.

Despite his refinements Schwartz’s Superman was still the same one as Mort Weisiger’s Earth-One Superman, albeit shorn of some of his more whimsical elements. There had never actually been a “hard reset” of Superman continuity. Then in the mid-1980s DC made the decision to eliminate the parallel worlds element of their universe and collapsed the histories of Earth-One and Earth-Two into a single timeline. That would have played havoc with characters like Superman who had distinct doppelgangers in different universes. So for clarity, and more importantly for economic reasons, DC retired the Earth-One Superman and hired writer/artist John Byrne to launch an entirely new version of the character.

Byrne’s version of Superman deliberately harked back to the less cluttered stories of the Earth-Two Superman, but after his departure the wider mythology slowly crept back into the stories. Writers including Dan Jurgens, Roger Stern, and Jerry Ordway transposed many of the old elements to the new stories and reimagined them to integrate them with the new history. However, the reboot of Superman’s continuity was not as clean as it should have been. His removal from the Legion of Superheroes was messy and was only successfully healed when the Legion were rebooted themselves in 1994. The post-1986 DC Earth was never officially named like the old parallel Earths, but fans have used the term Earth-Zero (after the 1994 Zero-Hour crossover). For all intents and purposes the Earth-Zero Superman would be Superman III although Byrne resisted DC’s attempts to label him as such and the character was never officially called that.

As Superman had changed so have the people reading his stories. Originally they were aimed purely at children and it was assumed that nobody would remember stories that were more than a few years old. This made traditional character development impossible. The break from Earth-One to Earth-Zero changed that philosophy and Superman’s status quo slowly began to alter. The first significant sign of this was Superman’s execution of three alien criminals – an act that left him with psychological repercussions that never really went away. Later on came the entire Death of Superman story arc that remains the highest profile story involving the Earth-Zero Superman. On a character level his sixty-year old status quo was irrevocably changed when Clark Kent revealed his secret identity to Lois Lane and the two married.

The Earth-Zero Superman’s adventures came sharply to an end with the Infinite Crisis. DC made a conscious effort to “break” their own characters. To introduce deliberate confusion in their histories (e.g. Superman: Birthright) and to play up instances where they seemed out of character. The heroes had fallen and that this new Crisis was to be their redemption. It also served to reintroduce the parallel worlds plot device by shattering the single universe into an infinite number of fragmentary universes that were then reassembled then into 52 different universes rather than the single Earth-Zero universe. Of these universes the so called “New Earth” Universe was to be the new primary universe. Large swaths its history matched that of Earth-Zero, but there are also large parts, particularly of the Superman canon, that have changed.

The 64,000 dollar question is whether we should consider the New Earth Superman as the fourth distinct primary incarnation (Superman IV) or as just an evolution of the Earth-Zero Superman. My gut feeling is that yes we should. The New Earth Superman is at the same place as a character as the Earth-Zero Superman was, but he arrived there by a slightly different route. More over, too much has changed about his backstory and his surrounding mythology and it is those things that define the different incarnations of the primary Superman more than his personality.