The worldwide oppression of women is the greatest moral issue of the 21st century, Pulitzer Prize-winning columnist Nicholas Kristof told a packed Graham Chapel Monday afternoon.

In the Assembly Series lecture, Kristof called on his audience, men and women alike, to join in fighting discrimination against women by getting out of their comfort zones.

“If only women are involved, then it is merely a marginalized struggle of the society,” Kristof said.

The New York Times writer came to campus to promote his book “Half the Sky: Turning Oppression into Opportunity for Women Worldwide,” which addresses the atrocities of social discrimination faced by women in underdeveloped countries such as India, Cambodia and Pakistan.

Kristof started his lecture by talking about how the idea for the book came to him and his wife and co-author, Sheryl WuDunn, when they visited China and noticed young girls dropping out of school.

Kristof discussed human trafficking, which, according to him, is one of the worst forms of “gendercide” and a form of 21st century slavery.

“More girls are killed in any one decade than people were slaughtered in all genocides of the 20th century,” Kristof said.

Kristof showed the audience pictures of women who were tricked or forced into prostitution, revealing the worlds these women have to face every day. He recalled a time when he saved a girl’s life by buying her from her pimp and got a receipt for it.

“When you get a receipt for buying a human in the 21st century, that should just be a shame on us all,” he said.

Kristof also touched on women’s health issues, citing examples of girls in Ethiopia who suffer from malnutrition while the male members in their families are in perfect health.

He told the story of a malnourished teenage girl named Mahabouba, who suffered a fistula while trying to give birth to her child but could not as a result of her underdeveloped pelvis, a common occurrence among girls in Ethiopia.

Kristof closed by discussing the measures taken in many places to ensure safety and health benefits for women. Kristof told the audience about medical reforms in Africa and about how women can be provided with microfinancing to start small businesses. Many of the women whose stories he told, such as Mahabouba from Ethiopia and Beatrice from Uganda, changed their lives because of their own determination and courage.

“Very modest amounts of money will help. People can transform the lives of people like Beatrice,” he said. “There is a way for people in St. Louis to make a real meaningful difference around the world.”

Kristof’s book is currently included as reading material for the Introduction to Women and Gender Studies class in the Women, Gender and Sexuality Studies department in Arts & Sciences. Students in the class responded positively to the presentation.

“The lecture was really good,” sophomore Ambica Sastry said. “A lot of the things that [Kristof] mentioned are from the book, but he supplemented the book more when he talked about his own personal experiences. That just gave a whole new dimension to the reading.”

Many students commented that the lecture brought forward previously-unknown information about human trafficking.

“The book opened my eyes to a huge problem in the world that’s not mentioned much in politics or media,” sophomore Sonya Rich said.

As a result of his work, Kristof’s travels have taken him around the world.

“Confusing, embarrassing experiences change our perspective and make us better human beings,” Kristof said. “I am just blown away by what I see.”

The George Warren Brown School of Social Work, the School of Law, the Association of Women Faculty, the Women, Gender and Sexuality Studies program, GlobeMed and Student Union co-sponsored Kristof’s lecture.

With additional reporting by Perry Stein.