Since the first wave of feminism hit the shores of the US in the early 20th century, the gender gap between men and women has been narrowing a lot and in many different ways.

Today colleges in the US graduate more women than men. More women work than men. And their salaries, though still generally lower, are inching toward the male levels.

But still, at the top of the tree, women are a lonely group. They make up less than 9 percent of global heads of state and 4 percent of the heads of Fortune Global 500 companies.

Many people have been trying to figure out the reasons. Social bias, corporate ecosystems that don't match women's needs and lack of affordable child care, are all listed as culprits. But few dare to blame the victims themselves.

Few, unless you are Sheryl Sandberg. The chief operating officer of Facebook recently published a book contesting that women have to be partly blamed for their own underachievement. The book calls women to aim higher, push themselves further out of their comfort zones, and not compromise work for family so easily.

Having a supportive husband, loving kids, a pretty face, a sharp brain, and at the same time, running a $104 billion company, Sandberg has all the reasons to tell women what's better for them and all the means to have people listen.

But whether women should follow their hormones or work against them, or, in other words, what role gender awareness plays in one's success or failure is still the focus of a heated debate.

Indeed, the battle for gender equality is no longer a simple question of a struggle between women and men. It is between women or men with their own identities.

The developments are clear in early education. Gender-specific toys have made controversial headlines during Christmas in recent years. And toy manufacturers have started to come up with ideas such as having Barbie roam around a construction site to ease criticism that they are enforcing gender stereotypes.

Last year, a 13-year-old girl collected 40,000 signatures on an online petition that eventually persuaded Hasbro to print images of boys on the boxes of their Easy Bake Ovens as well, so that her younger brother, who wanted it for a gift, wouldn't think he was playing with a girl's toy.

Yet amid the gender blending trend is the return of single sex schools in the US.

According to the National Association for Single Sex Public Education (NASSPE), 10 years ago there were only a dozen public schools in the country that offered single sex classrooms. The number has jumped to more than 500 now.

Of those about one-fourth are in schools that are entirely single sex, reflecting the increasing popularity of the belief among some educators that the different needs of boys and girls should be tended separately.  

But this is not without conflicts. The American Civil Liberties Union has been trying to fight back and has filed lawsuits against some of these schools on the basis of gender segregation. And NASSPE has recently taken down a list of the schools from its website to protect members.

In Europe, an opposing effort caused no less controversy. Egalia, a public kindergarten opened in 2010 in Sweden, has been trying to tune down the gender identities of kids by encouraging them to play with the same toys and avoid using the gender-oriented words such as "boys," "girls," "he" or "she."

While some experts welcome the idea, others think this will make kids confused and ill-prepared for the real world. And some even describe it as brainwashing.

During the Maoist era in China, the idea of gender equality was forced into a longtime patriarchal society by wiping out gender characteristics with uniform clothes and thoughts.

It only led to a boring looking country submerged in an ocean of blue and grey. And the awakening of gender identity since then has created a colorful country as well as inequalities in education and job opportunities.

It's hard to say which side of the battle will win, or which side is right. Before making such judgments, one has to face a key question: Exactly how much difference you can keep on the road of pursuing equality? It could take a few generations to come up with an answer.      

The author is a New York-based journalist. rong_xiaoqing@hotmail.com