One of the hallmarks of the great mythical hero is that he or she is apart from society—an outcast. Sure, Robin Hood may steal from the rich and give to the poor, but what thanks does he get? He’s branded an outlaw, hounded by the authorities, and forced to live in the forest.

So it is with Marvel Comics’ Uncanny X-Men, heroes who, while maybe not possessing the household name of a Superman or Spider-Man, have defined the pinnacle of comic book success during the past five decades.

The X-Men were created by two of comicdom’s most legendary figures, writer Stan Lee and artist Jack Kirby, in 1963. Lee and Kirby envisioned a team of young mutants—people born with special powers—living at a school for the gifted, where, under the tutelage of the telepathic “Professor X,” they secretly would learn to harness their unique abilities and use them for the good of mankind. They were stock teenagers straight out of Central Casting: one shy, one awkward, one fun-loving, one self-absorbed, one wisecracking. Sales of the title foundered.

Then, in 1975, Marvel released Giant Sixe X-Men #1 and everything for the X-Men—and the world of comics—changed forever. The most notable difference in these “All-New, All Different” X-Men was their diversity. The team now featured characters of different colors from all over the world: Kenya, the Soviet Union, Japan, West Germany, Ireland, and Canada. A Native American character also was featured.

As the adventures of these new X-Men were chronicled, their “otherness” was more strongly emphasized, as was the mistrust of mutants by the inhabitants of the fictitious Marvel Universe. Written by Len Wein and later by long-time X-scribe Chris Claremont, the X-Men were now “sworn to protect a world that hated and feared them.” The Xavier School for Gifted Youngsters became a refuge for young mutants who were despised simply because of how they were born. They were misfits, outcasts, and disenfranchised. In short, they were the heroes with which every young comic book reader who had ever felt “different” could immediately identify. X-Men sales skyrocketed, setting new standards for the industry. In the wake of this success, multiple X-Men spin-off titles and characters were created.

The unique nature of the X-Men’s popularity wasn’t lost on its creators. Soon, the franchise was overtly dealing with themes of bigotry, prejudice, and racism. Professor X, like Martin Luther King Jr., envisioned a world in which humans and mutants could live in peace. Magneto, the mutant master of magnetism, sought to protect mutantkind “by any means necessary,” echoing the words of Malcolm X. Mutants were often the victims of mob violence, as African Americans had been for generations. Beginning in the 1980s, an X-Men storyline featured mutants being segregated on the island of Genosha, recalling the struggle of black citizens under South African apartheid.

The X-Men’s exploits in comics and films have also mirrored the struggles of other American minority groups. Magneto was revealed to be a Jewish survivor of the Holocaust who was experimented on as a teenager. “I’ve been at the mercy of men just following orders,” he tells Professor X in X-Men: First Class (2011). “Never again.” The religious backgrounds of other team members, including the Catholic Nightcrawler and Dust, a devout Muslim, have also been woven into X-Men storylines.

As sexual orientation became a more prominent issue in American society, so too did the struggle for LGBT rights reflect in the adventures of the X-Men. After Bobby “Iceman” Drake “comes out” to his parents as a mutant in X-Men 2 (2003), his mother asks, “Have you tried not being a mutant?” In the pages of the X-Men comics, several gay and bisexual characters, including Destiny, Shatterstar, Karma, and Courier appeared. In 2012, the mutant Northstar was wedded in a same-sex marriage. Two decades earlier, a disease known as the Legacy Virus, a clear analogy of the AIDS epidemic, swept through Marvel’s mutant population, killing hundreds before turning its attack on humans.

Like the X-Men themselves, comic book fans are a remarkably diverse group. The vast majority of them, however, have something in common: at one time in their lives, they’ve felt as if they’re different, as if they’ve been set apart from a world that doesn’t understand them, as if they’re outcasts. Who among us can say they’ve never felt that way? In this aspect, we’re all the same, and therein lay the essence of the X-Men’s appeal: at heart, we’re all mutants. In the end, we’re all X-Men.