You've probably heard about Constance McMillen by now. She's the openly-gay high school senior who wanted to take her girlfriend to the high school prom at Itawamba High School in northern Mississippi. The principal told the girls that all prom couples have to be boy-girl. Ms. McMillen called the ACLU, which threatened the school with legal action. In response, the school board canceled the prom. The ACLU then asked U.S. District Court Judge Glen Davidson to intervene and reinstate the prom. The judge ruled that although the school had violated Ms. McMillen's civil rights, he wouldn't force them to hold a prom. On Friday, April 2, Ms. McMillen attended an alternative prom at the Fulton County Country Club. According to the Associated Press, her girlfriend's parents wouldn't allow the 16-year-old girlfriend to go, so McMillen escorted another young woman instead. To make the story even worse, it turns out that the alternative prom at the Fulton County Country Club was a fake, with only seven kids attending, according to McMillen. The real prom, i.e., the prom which most of the seniors attended, was held at a still-undisclosed location, and McMillen wasn't invited.

The story continues to attract national because it's just so darn quaint. Imagine: There are still people who get upset when they see girls kissing other girls! Who knew?

Psychologist John Buss estimates that for most of human history, perhaps 2% of women have been lesbian or bisexual (see note 1, below). Not any more. Recent surveys of teenage girls and young women find that roughly 15% of young females today self-identify as lesbian or bisexual, compared with about 5% of young males who identify as gay or bisexual (see note 2, below).

As a physician and a psychologist, what I found missing in the noise surrounding the Constance McMillen story was any serious discussion of why a growing number of girls self-identify as lesbian or bisexual. Not that there's anything wrong with that, as Seinfeld might say. But why are young women today at least three times more likely than their brothers to identify as bisexual or homosexual? "I kissed a girl and I liked it," Katy Perry told us in her #1 hit single. Megan Fox, Lindsay Lohan, Lady Gaga, Anna Paquin, Angelina Jolie, Drew Barrymore—they all want us to know that they are bisexual. There is no comparable crowd of young male celebrities rushing to assure us that they go both ways. Imagine a young man singing "I kissed a boy and I liked it." Would that song reach #1 on the charts? Why not?

Why is it OK for girls to be bisexual or homosexual, but not boys?

Over the past seven years, I've posed this question to hundreds of teenagers and young adults across the United States. The most common answer I get isn't really an answer. "Girls kiss other girls at parties because guys like it," one teenage girl told me. "It makes the guys hoot and holler, so the girls do it again. They're just doing it for attention. It's not for real."

I point out, as gently as I can, that that response doesn't answer my question. Pretending to be lesbian or bisexual doesn't explain why a growing proportion of young women are lesbian or bisexual.

Or does it?

Female is different from male sexuality. If a straight boy kissed another boy, perhaps to amuse some girls who might be watching, he would be unlikely to undergo a change in as a result. But, as Professor Roy Baumeister at Florida State University and others have shown, sexual in many women seems to be more malleable (see note 3 below). If a teenage girl kisses another teenage girl, for whatever reason, and she finds that she likes it—then things can happen, and things can change. If a young woman finds her soulmate, and her soulmate happens to be female, then she may begin to experience feelings she's never felt before.

Especially if all the guys she knows are losers.

Which brings me to the second point I've encountered in my interviews with young people. Twenty years ago, when I opened my practice in a suburb of Washington DC, it was rare to find 14-year-old boys who were looking at every day. Today it's common—in fact, it's becoming the norm. When I meet with a group of 14-year-old boys and I ask them, "how many of you guys subscribe to a porn site?", all hands go up. I don't believe them. But today, no boy wants to admit that he's the weirdo who doesn't look at online porn. Twenty years ago, hardcore pornography was tucked away in adult bookstores. Today any 14-year-old can access such photos online in seconds. Role models for young men, from pop singer John Mayer to the 2009 World Series MVP Hideki Matsui, talk openly about their collections of porn (see note 4, below).

Is there any connection between these two trends—between the rise in the number of young women who self-identify as lesbian or bisexual and the increasing normalization and acceptance of pornography in the lives of young men? Maybe there is. A young woman told me how her boyfriend several years ago suggested that she shave her pubic hair so that she might more closely resemble the porn stars who were this young man's most consistent source of sexual arousal. She now identifies herself as bisexual. "It was just such a welcome change, to snuggle under a blanket on the couch with my girlfriend, watch a movie, and talk about God and death and growing old, to be intimate emotionally and spiritually as well as physically. I don't know a guy who could even comprehend the conversations we have."

I wish Constance McMillen and her girlfriend all the best. But I have to wonder: Are there so many girl-girl couples out there because the guys are such losers?



Note 1: How common has bisexual and lesbian sexual orientation been among women, historically?: In the third edition of his textbook : the new science of the mind, Professor David Buss (University of Texas / Austin) asserts that "1 to 2 percent of women" are lesbian or bisexual ("What about lesbian sexual orientation?" Box 4.1, p. 137 in the Pearson International Edition, 2009). He implies that this figure has been generally valid over time, a finding which he acknowledges poses an as-yet-unsolved mystery for evolutionary psychology. Popular accounts of homosexual behavior often suggest that these behaviors make evolutionary sense because the people practicing these behaviors make better aunts and uncles than heterosexuals do, a theory first advanced by E.O. Wilson back in the 1970s. However, studies published in the past 20 years have provided little support for this hypothesis, and have often directly refuted it, particularly for male homosexuals. It turns out that gay men are actually more likely to be estranged from nieces and nephews, which contradicts the predictions of Wilson's kin theory: see for example Bobrow & Bailey 2001, also Rahman & Hull 2005. (Nobody seems to have told The New York Times about this, as they repeated E. O. Wilson's 1970s hypothesis about homosexual men being better uncles, with breathless credulity and no substantive mention of the studies refuting this theory, in a lengthy March 29, 2010 feature in The New York Times Magazine.)

It's very difficult to estimate accurately the "true" proportion of lesbian or bisexual women 50 years ago or 200 years ago. In many jurisdictions 50 years ago, lesbian behavior would have been a criminal offense. In that era and in those jurisdictions, asking a woman whether she was a lesbian was equivalent to asking her whether she had committed a . Even when assured of confidentiality, women might reasonably under-report the true incidence of bisexual or lesbian orientation.

However, it's hard to deny that lesbian and bisexual behavior has become much more visible in our time compared with one or two generations ago.

Note 2: How common is bisexual and homosexual orientation, today? Researchers at Cornell University, examining data collected from a representative sampling of young Americans which included more than 20,000 individuals in 80 communities across the United States, found that 85.1% of the young women identified as heterosexual; 0.5% reported no sexual ; and the remaining 14.4% were sexual but not strictly heterosexual, i.e. either lesbian or bisexual. Among young men, 94.0% identified themselves as heterosexual; 0.4% of the men reported no sexual identity; and the remaining 5.6% identified as gay or bisexual. See Ritch Savin-Williams and Geoffrey L. Ream, "Prevalence and stability of sexual orientation components during and young adulthood," Archives of Sexual Behavior, volume 36, pp. 385 - 394, 2007. The proportions in Europe might be higher. For example, in Norway, more than 20% of girls and young women identified as lesbian or bisexual: see L. Wichstrøm and K. Hegna, "Sexual orientation and attempt: A longitudinal study of the general Norwegian adolescent population," Journal of Abnormal Psychology, volume 112, pp. 144-151, 2003. In a study from New Zealand, 16.4% of young women identified as lesbian or bisexual, compared with 5.6% of men who identified as gay or bisexual: see N. Dickson and colleagues, "Same-sex attraction in a birth cohort: prevalence and persistence in early adulthood", Social Science and Medicine, volume 56, pp. 1607 - 1615, 2003.

Note 3: Maybe a straight woman is just a woman who hasn't yet met—the right woman? Professor Roy Baumeister's most relevant article about erotic plasticity is " differences in erotic plasticity: the female sex drive as socially flexible and responsive," Psychological Bulletin, volume 126, pp. 347 - 374, 2000. Professor Lisa Diamond has made a compelling case that many women don't discover their "true" sexual identity until their 20s, 30s or even 40s. A woman may reach her 40s, believe that she is a straight woman, and then find herself falling in love with her soulmate—who happens to be a woman. Here are three of Professor Diamond's most relevant articles:

"Female bisexuality from adolescence to adulthood: results from a 10-year longitudinal study," Developmental Psychology, volume 44, pp. 5 - 14, 2008.

"The evolution of plasticity in female-female desire," Journal of Psychology and Human Sexuality, volume 18, pp. 245 - 274, 2006.

"What does sexual orientation orient? A biobehavioral model distinguishing and sexual desire," Psychological Review, volume 110, pp. 173 - 192, 2003.

Note 4: John Mayer said what? John Mayer's current preference for pornography over sex with real women wasn't well-known until his interview with Rolling Stone (February 4, 2010) and his March 2010 interview with Playboy magazine, in which he also explained why he now prefers porn over sex with actual women: because allows him to be in complete control. He said: "As soon as I lose that control, once I have to deal with someone else's desires, I cut and run ... I'm more comfortable in my imagination than I am in actual human discovery."