On Friday the United Nations is set to appoint Wonder Woman its "Honorary Ambassador for the Empowerment of Women and Girls." The cartoon character, turning 75 this year, will be the face of a social media campaign that the U.N., will launch at a star-studded ceremony in New York. The actress Gal Gadot — who plays Wonder Woman in the movies these days — is scheduled to be there. So is Lynda Carter, who portrayed the superhero in the 1970s television show.

But the decision has outraged many women's rights advocates, including hundreds who've signed a petition against it.

"It's an insult, frankly," says Anne Marie Goetz, a professor of global affairs at New York University and a former adviser on peace and security issues to the United Nations agency, U.N. Women. She says a big issue is the timing.

The U.N.'s anointing of Wonder Woman has actually been in the works since last spring. That's when Warner Brothers and DC Comics — which owns rights to the character — approached the U.N. about celebrating her 75th birthday and an upcoming movie with a joint social media campaign promoting women's rights through tweets and Facebook call-outs.

But news of the plan only started to filter to women's rights advocates over the last week — right on the heels of a disappointing, year-long grassroots effort to get the U.N. to choose its first female Secretary General.

"This was months and months of campaigning by feminist organizations around the world for a woman to be selected," says Goetz.

Seven women — including a prime minister and other highly qualified individuals — were in the running, an unprecedented number. But earlier this month the Security Council went with a man — Antonio Guterres. So the selection of Wonder Woman to represent women's issues for the U.N. came off to Goetz and others as a sort of demeaning consolation prize.

"It's frivolous, it's fatuous and it reduces an extremely serious human rights problem experienced by half of the world to a cartoon," she says.

And not just any cartoon, adds Goetz. Wonder Woman in her view looks like a Barbie/playboy pinup. Like most female comic action figures she's got big breasts bursting out of a skimpy outfit and an impossibly tiny waist.

"The message to girls is that you are expected to meet a male standard in which your significance is reduced to your role as a sexual object," says Goetz.

Maher Nasser, the U.N. official who essentially brokered Wonder Woman's appointment, says he and other U.N. colleagues were aware of those concerns.

"I mean we have had these discussions, of course, with our partners," says Nasser, who directs the Outreach Division of the U.N.'s Department of Public Information, which handles partnerships with celebrities and entertainment figures.

Nasser says his team worked closely with artists at DC Comics to tone down the image that will be used in the U.N. campaign.

"The campaign art that we are working with ... doesn't have that caricature image of the wrong stereotype of what a woman should look like."

They're only showing Wonder Woman from the waist up. And she's got this cape draped round her neck and shoulders, making her bust less prominent.

And Nasser says the social media campaign they're planning will be all about emphasizing Wonder Woman's girl power credentials, what he calls "the essence of the character."

"The focus [of the U.N.] was on her feminist background, being the first female superhero in a world of male superheroes and that basically she always fought for fairness, justice and peace," says Nasser.

Wonder Woman certainly has some solid feminist roots, says Jill Lepore, a professor at Harvard University who wrote a book about the comic book character's creation: The Secret History of Wonder Woman.

She was invented in 1941 by William Moulton Marston, a Harvard-trained Ph.D. psychologist-cum-advice columnist for Family Circle magazine. Marston had been brought on board by the company that eventually became DC Comics to help deal with a public relations problem.

The company's first two superheroes, created in the late 1930s, had become controversial. "Superman looked a bit like a fascist — he's an ubermensch. Batman carried a gun and was quite violent," explains Lepore.

It had gotten to the point where various religious and parental groups had banned the comics.

"So Marston said, 'You know, you need a female superhero because she will embody the nurturing values of womanhood. She will be about peace not war.'"

The character he then set about creating drew largely on a real-life woman Marston knew personally and greatly admired: Margaret Sanger, the co-founder of Planned Parenthood.

In the comic book, Wonder Woman is a princess of the Amazons of Greek mythology, living on an island where there are no men. That story, says Lepore, "comes not from science fiction but from feminist utopian fiction" popular with Sanger and other early feminists of the progressive era. (In the cartoon, a U.S. Army officer Captain Steve Trevor crash lands on the island. Wonder Woman rescues him and then resolves to go with him to America to fight for democracy and equal rights.)

Marston had an ambitious vision for his new character, laid out in a remarkable press release, distributed soon after her debut. He stated: "The only hope for civilization is the greater freedom, development and equality of women in all fields of human activity. He added, "Frankly, Wonder Woman is psychological propaganda for the new type of woman who should, I believe, rule the world."

Yet even in her earliest years Wonder Woman embodied contradictions. It wasn't just the risqué outfits. Marston insisted that in every episode Wonder Woman had to be tied up or otherwise bound by the villain.

In part, says Lepore, this was a nod to the iconography of the suffragettes of the early 1900s, who often wore chains on marches seeking the right to vote. But it also became clear from letters to DC Comics that Wonder Woman's largely male audience found this aspect of her story titillating.

Today, that bondage theme — at a time when women are under threat from extremist violence around the world — is just one more reason activists like Goetz are uncomfortable with the idea of Wonder Woman as a U.N. ambassador.

Wonder Woman nonetheless remained a darling of feminists through the 1970s — she was on the first cover of Ms. Magazine. But by the end of that decade she had started to symbolize a split within the feminist movement.

"A lot of people started to say, 'Why is she the symbol of women's power? She's just so obviously made for men to look at and ogle,'" says Lepore.

It's no surprise that Wonder Woman continues to spark debate, Lepore adds. "Part of the richness of this character is that there are many layers to understanding her. Wonder Woman is always going to have a mixed legacy."

So today Wonder Woman means different things to different people at different times. A case in point: Maher Nasser the U.N. official. He grew up reading comics and was inspired by Wonder Woman's fight for justice.

"For me these values are what brought me to the United Nations."

But when I ask him what she represents for him at this particular moment, he lets out a rueful chuckle.

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