(or "The Amazing Evolution Of J'Onn J'Onzz")
At times, it sometimes seems like there's a Darwinian element to the way storytelling engines function. In fact, there most definitely is--with a finite amount of resources (to wit, dollars in the budget of comics fans) and a process of change over time, the theory of natural selection dictates that comics that can adapt themselves to produce the most exciting and interesting stories for the reading audience will survive, and that changes that increase reader interest will stick around, while changes that don't will perish. (This, in a totally random aside, is why Lex Luthor is never going back to the pre-Crisis version, no matter how hard writers like Jeph Loeb and Mark Waid push for it. The suave, corporate raider Luthor is just a more interesting character. Survival of the most interesting.)
So how does this relate to J'Onn J'Onzz, Manhunter from Mars? Because like all good species in a Darwinian world, he has adapted to survive--and the recent 'Showcase Presents The Martian Manhunter' preserves that evolution, like a fossil, for our edification. The Martian Manhunter, as it happens, was around during a very tumultuous period in comic book history, the beginning of the Silver Age of comics. (In fact, some people claim him as the first Silver Age character, a point I'm about to profoundly dispute.) And, like those tiny little mammals right around the end of the Cretaceous era, he suddenly found himself in a period of big environmental upheaval and had to adapt to survive. Let's look at his two storytelling engines in chronological order, along with the "meteor" that hit comics in the meanwhile.
Storytelling Engine #1: J'Onn J'Onzz, a martian accidentally stranded on Earth by a dead scientist, decides to help humankind while he tries to find a way home by masquerading as a human police officer with his shapeshifting abilities. He solves crimes as "John Jones", all the while secretly using his Martian powers to aid him in his detecting.
At the time, this was just one of many quirky "detective" comics that dotted the newsstand. (In fact, it ran as a backup in 'Detective Comics', home of Batman.) They had ghost detectives, detective chimpanzees, and detectives from the future, so a detective from space probably fit right in. "Detective comics" were one of several mini-trends that populated this era of comics, along with science fiction, westerns, horror, and romance...but very few superheroes. In fact, apart from Batman, Superman and Wonder Woman, DC wasn't publishing any "superhero" comics at all.
Then along came Julius Schwartz, and the Silver Age hit comics like the proverbial meteor. Schwartz sensed the enthusiasm for science fiction comics was about to boom, and so he relaunched almost every major DC hero from the Golden Age as a science-fiction themed character. From 1956 to 1960, the Atom, Hawkman, Green Lantern, the Flash, and the Justice Society were all recreated as sci-fi heroes, and comics readers couldn't get enough. So what did this mean for J'Onn J'Onzz?
Storytelling Engine #2: Suddenly (in November 1959, to be exact), the arrival of an "evil Martian" meant that he had to reveal his existence to the public or be framed for crimes he didn't commit. He kept "John Jones" as a secret identity, but transformed into "The Martian Manhunter", complete with costume, when he needed to fight crime. Occasional guest-star Diana Meade became a regular character, and suddenly developed a suspicion that John Jones and the Martian Manhunter might be one and the same. Within a few months, he even joined a super-team (the newly-formed Justice League of America), completing his transformation from "quirky detective" to "super-hero".
It's pure Darwinian evolution in action. The property completely transformed itself to attract new readers, while other characters less suited to do so fell into obscurity for many years. (Detective Chimp is just now making his comeback in the DC Universe.) What does this mean for Marvel and DC today? Perhaps it means they need to keep their options open. Nobody wants to just chase the next trend, but chasing it is a better option than being run over by it.