Wonder Woman. (Photo: DC Entertainment/Warner Bros.)

Female superheroes are ascendant. Wonder Woman's featured role in Batman v Superman: Dawn of Justice (and her highly anticipated 2017 solo film) comes on the heels of Scarlett Johansson's Black Widow and a slew of female X-Men. Meanwhile, on the small screen, Netflix's Jessica Jones, a drama about a troubled private detective with super strength, and CBS's Supergirl, a drama about Superman's cousin, have proven to be hugely popular franchises.

Female superheroes are nearly as old as the genre itself. Wonder Woman burst onto the comic book scene in 1941, as a strong—if scantily clad—feminist (and pacifist). But in the world of super powers, Wonder Woman was an exception, not the rule; most women in the genre were plot points rather than heroes themselves. And when they did appear as more than damsels in distress, superheroines have most often been portrayed as one-dimensional characters—better examples of cisgender males' physical feminine ideals than bastions of feminism.

Generally speaking, a woman's dominance has long been linked to her beauty. Consider, for example, reports that a picture of Rita Hayworth—one of America's favorite and earliest "bombshells"—was attached to the first nuclear bomb tested by the American military after World War II. And this pattern of judging a woman's power primarily by her looks continued well into the 21st century. "Modern female characters are so thoroughly eroticized that it is nearly impossible to find a superheroine or villainess that is not defined primarily by her sex appeal," Jeffrey Brown, an associate professor at Bowling Green State University, wrote in 2011.

A woman's dominance has long been linked to her beauty.

That holds true even for superheroines with complex storylines and abilities to rival their male co-stars. In 2012's The Avengers, Johansson's Black Widow was strong and multidimensional, and got more screen time than Hulk or Thor. But it was Johansson's physical appearance, rather than her character's storyline, that took center stage in much of the media discourse about Black Widow. As Marc Dipaolo, an associate professor at Oklahoma City University, wrote in 2013: "A lot of online discussion and gossip magazine ink around this film was dedicated to describing Johansson's crash vegan diet, which enabled her to sculpt her body to the form-fitting black catsuit."

Female characters' physiques are shaped by male preferences—comic book artists know their audience. But drawings of bodacious superheroines can actually shape male preferences for real world women. A 2002 study, for example, found that, when college-age men were shown pictures of comic book women, the images had a measurable effect on their description of an ideal real-life woman. Compared to men who were shown pictures of real women, the test subjects preferred women with bigger breasts and muscles.

But a sea change in fearless female characters is underway, as Jennifer Keishin Armstrong pointed out in BBC Culture:

The new breed of superheroine, represented by Jessica Jones and Wonder Woman, has stopped pandering to the male gaze. Make no mistake: the women playing these characters are still freakishly beautiful. But Jessica Jones, at least so far, fights evil fully clothed in practical garments: jeans, leather jackets, T-shirts, boots. Gadot's Wonder Woman still wears a bodysuit, but she looks more like Beyoncé in full power position at the Super Bowl than a Victoria's Secret model posing in the boudoir. The female Ghostbusters, of course, fully embrace the janitorial jumpsuits of their male predecessors. And Supergirl actually has its heroine fret on screen over the feminist implications of her costume.

This is great news for the young women who look up to these heroines. Adolescent girls develop their identities in part by imitating the women they see portrayed in the media, according to the American Psychological Association, and sexualized representations of women can teach young girls that their value as human beings stems primarily from their sex appeal. Programming that teaches girls that females are little more than sexual objects starts young—remember Lola Bunny from Space Jam? (OK, to be fair, Lola was no superhero, but she was a better baller than her male teammates, and, honestly, why did she need to be in a crop top?) Not much has changed since Space Jam was released in 1996; even today, nearly 30 percent of female characters in family movies are dressed in what might be described as "sexy attire," while only eight percent of male characters are dressed provocatively.

These sexualized representations can be particularly harmful because the representation of gender in television and the movies is so lopsided. It's relatively rare to see females at all, let alone complex female characters who serve as more than just eye candy for male co-stars and audience members: Seventy-five percent of the top movies that came out between 2012 and 2013 featured male leads, Francie Diep reported earlier this year in Pacific Standard.

And if superheroes are to be effective role models for young fans, diversity is crucial. "It's good to have diversity—a pantheon of different characters that will fit better for different people looking for characters that look like them, that have similar histories and aspirational goals," says Robin Rosenberg, a clinical psychologist with a special interest in superheroes. Super role models are well equipped to teach kids about morality, serving the community, and finding meaning out of adversity, but only if kids can relate to, or see something of themselves in, their heroes.

The actual comic books themselves, which have long been progressive in issues related to race, the environment, and drugs, are finally making moves toward gender equality as well. A 2013 study of gendered language in modern comics found that male and female superheroes are at least equal in their manner of speech. (Comic book readers were still more likely to describe female superheroes for their physical looks than their physical abilities.) Women currently make up one-quarter of comic book characters. Behind the scenes, women are even more outnumbered; one study found that women make up just 12 percent of Marvel comics' editors, writers, and artists, and only 10 percent of DC Comics'.

And mainstream representations of superheroines do not always support progress toward gender parity. Last year, Katie Kilkenny reported for Pacific Standard on the work of Katy Gilpatric, a sociologist at Kaplan University. Gilpatric found that "violent female action heroes" in movies actually reinforced gender stereotypes; they were violent in typically masculine ways, but they were also usually submissive to their male action hero cohorts, served as love interests, and frequently died before the conclusion of the film. And these hypermasculine and hyperfeminine mash-ups can lead viewers to expect too much of real world women, Kilkenny found: "Failing to live up to these super-expectations comes at a cost.... The superwoman ideal is frequently linked to eating disorders. Others have said it increases the risk for professional burnout, bad health, and unhealthy relationships."

In other words, a female superhero is not necessarily a feminist hero. And while Wonder Woman's appearance in Batman v. Superman is good news for both Batman and Superman—not only does she save the pair in the trailer, but her character seems to be a lone ray of hope in a world of negative reviews—and for female fans of the superhero genre, she's still just one woman on a team of male heroes.