The men and girls in the photos hold hands and embrace – the young women are in long white dresses, the men in suits or military regalia. If some of the girls in the pictures weren't so young - Laila and Maya Sa up there are seven and five years old, respectively - the portraits could be mistaken for wedding or prom pictures. What they actually capture, though, are images of those who participate in purity balls – father-daughter dances featuring girls who pledge to remain virgins until marriage and fathers who promise to protect their daughters' chastity.

The images from Swedish photographer David Magnusson's new book, Purity, are beautiful, disturbing and tell a distinctly American story – a story wherein a girl's virginity is held up as a moral ideal above all else, a story in which the most important characteristic of a young woman is whether or not she is sexually active. This narrative of good girls and bad girls, pure girls and dirty girls, is one that follows young women throughout their lives. Purity balls simply lay that dichotomy bare. In a clip from a Nightline Prime episode on these disconcerting events , a father tells his braces-clad daughter, "You are married to the Lord, and your father is your boyfriend." (Update: As part of a purity event over the weekend sponsored by the Las Vegas police department, one of its officers told girls that if they had pre-marital sex they would end up rape victims, gang members, drug addicts or prostitutes.)

While it would be easy to dismiss purity balls as fringe – most American fathers don't require their daughters to pledge their virginity in an elaborate ceremony – the paternalism and fear of female sexuality underlying the events are present throughout American culture. (I wrote about this phenomenon in my 2009 book, The Purity Myth: How America's Obsession with Virginity is Hurting Young Women.)

The idea of girls' chastity as a mobilizing force in culture and politics may feel like a throwback, but it's something that still tangibly impacts thousands upon thousands of modern women – even through policy.

For example, it took the US Food and Drug Administration (FDA) years to approve emergency contraception – also known as Plan B – for over-the-counter status. Why? Because of fears that teenage girls would become promiscuous. An internal memo showed that Janet Woodcock of the FDA was concerned that increased access to the contraceptive could cause "extreme promiscuous behaviors such as the medication taking on an 'urban legend' status that would lead adolescents to form sex-based cults centered around the use of Plan B."

Yes, teen sex cults.

When the FDA finally did recommend Plan B become available on pharmacy shelves, Health and Human Services Secretary Kathleen Sebelius publicly overturned the agency's decision. When President Obama voiced his support for the unprecedented move, he invoked fatherhood and protectionism: "As the father of two young daughters, I think it is important for us to make sure we apply some common sense to various rules when it comes to over-the-counter medicine." Apparently fatherly concern was meant to trump science. As Ann Friedman wrote last year at New York magazine, "Obama may be setting policies based on his preteen daughters, but all women have to live with the consequences."

American paternalism and patriarchy also reared its head recently when Harvard professor Dr Kimberly Theidon filed a discrimination suit against the college, claiming she was denied tenure because of her work supporting sexual assault victims. (Harvard is one of the 55 colleges and universities named by the Education Department on Thursday as currently under federal investigation for mishandling sexual violence and harassment on campus.) Theidon alleges she was told numerous times to be a "dutiful daughter" if she wanted to succeed at the college.

Facebook Twitter Pinterest 'I realize that my biggest dream is to go to France, and I can't do that if I get pregnant before marriage,' says Erin Hope Smallwood, 13, pictured at left with her father, Jay, in Haughton, Louisiana. At right in Tuscon, Arizona, 17-year-old Nicole Roosma and her father, Will. 'With everything being about sex through the culture and around us,' she says, 'it's especially hard for my generation to keep a promise like this.' Photographs: David Magnusson

Magnusson says he hopes his pictures elicit empathy,not judgment:

As I learnt more, I understood that the fathers, like all parents, simply wanted to protect the ones that they love – in the best way they know how.

I have no doubt that families who participate in purity balls are doing what they think is best for their children – but that doesn't make them any less wrong. When we teach girls that their virginity makes them special and valuable, we're sending the simultaneous message that without their virginity they are tainted and damaged.

Take Elizabeth Smart – now an activist against child abuse and sexual exploitation – who was kidnapped when she was 14, raped and held for nine months before she escaped. At a forum last year, Smart talked about the way that abstinence-only education made her feel "dirty and filthy" after she was raped. "That's how easy it is to feel like you no longer have worth, you no longer have value. Why would it even be worth screaming out? Why would it even make a difference if you are rescued? Your life still has no value."

But our lives do have value, whether we're "chaste" or not. Too bad there's no party for that.