By JANE E. BRODY
In last summer's prize-winning R-rated film \"Me and You and Everyone We Know,\" a barely pubescent boy is seduced into oral sex by two girls perhaps a year older, and his 6-year-old brother logs on to a pornographic chat room and solicits a grown woman with instant messages about \"poop.\"

Is this what your teenage children are watching? If so, what message are they getting about sexual mores, and what effect will it have on their behavior?

The journal Pediatrics addressed the topic last July in a supplemental report, \"Impact of the Media on Adolescent Sexual Attitudes and Behaviors.\" It is an important and, sad to say, much neglected subject. The report, based on a thorough review of scientific literature, was requested by Congress and supported by the Centers for Disease Control and Prevention and the University of Texas Health Science Center at Houston.

A Neglected Subject Pursued

I'll start with the bottom line: \"Although a great deal is known about the effects of mass media on other adolescent behaviors, such as eating, smoking and drinking, we know basically nothing about the effects of mass media on adolescent sexual behaviors,\" the report's principal investigator, S. Liliana Escobar-Chaves of the university's Center for Health Promotion and Prevention Research, concluded.

But to hazard a guess based on clear evidence that media representations influence teenage eating, smoking and drinking habits, adolescents are almost certainly affected — negatively — by sexual references and images from television, in movies and video games, in music, in magazines and on Web sites.

Who's monitoring what teenagers see, read and hear about sex? For the most part, no one. \"There is growing concern that youth are accessing media in environments isolated from the supervision or guidance of parents or other adults,\" the report says. \"The average American youth spends one-third of each day with various forms of mass media, mostly without parental oversight.\"

Despite the advent of V-chips, movie ratings and televised warnings of appropriateness for young people, American teenagers have no trouble getting access to graphic sexual presentations. And no one restricts what they hear in popular songs. The effect of abstinence-only education pales by comparison with the many graphic messages that portray sexual activity — especially unprotected sex outside of marriage — to be a part of our culture as normal and acceptable as eating a Big Mac or drinking a Coke.

The proportion of high school students who say they have had sex has declined some and the rate of teenage pregnancies has dropped, but the numbers remain staggering. The report states: \"Approximately 47 percent of high school students have had sexual intercourse. Of these, 7.4 percent report having sex before the age of 13, and 14 percent have had four or more sexual partners.\"

Each year, nearly 900,000 teenage girls in the United States become pregnant (340,000 are 17 or younger). The rates of sexually transmitted diseases are higher among teenagers than among adults, and 35 percent of girls have been pregnant at least once by age 20. In 2002, chlamydia infections were six times as prevalent among sexually active adolescent girls as they were among sexually active women.

The risks don't end with pregnancy and disease. \"Data suggest that sexually active adolescents are at high risk for depression and suicide,\" the report states. \"Early sexual experience among adolescents has also been associated with other potentially health-endangering behaviors, such as alcohol, marijuana, and other drug use.\"

In an accompanying article, Dr. Joe S. McIlhaney Jr. of the Medical Institute for Sexual Health in Austin, Tex., wrote, \"Many parents and some physicians underestimate the negative and lifelong impact of early sexual activity.\" The main report said that, in hindsight, many sexually active teenage girls wished they had waited longer.

Exposure Is Widespread

Television is the best-studied medium, and the average teenager watches it for more than three hours a day. Two-thirds of youngsters 8 to 18 have TV's in their bedrooms, and two-thirds live in homes with cable TV, providing unsupervised access to sex talk and scenes.

The sexual content of TV is pervasive and increasing. A Kaiser Family Foundation study found that \"the shows most watched by adolescents in 2001-2002 had 'unusually high' amounts of sexual content compared with TV as a whole: 83 percent of programs popular with teens had sexual content, and 20 percent contained explicit or implicit intercourse.\"

\"On average,\" it continued, \"each hour of programming popular with teens had 6.7 scenes that included sexual topics.\"

The foundation study found that \"characters involved in sexual behavior in TV programs rarely experience any negative consequences.\"

\"Programs with a primary emphasis on sexual risk and responsibility themes represent only 1 percent of all shows that contain sexual content,\" it continues. Furthermore, only 3 percent of sex scenes observed involved protection against disease and unwanted pregnancy.

What little is known about the effects of television sex on teenage attitudes and behavior comes primarily from a national telephone survey conducted twice, in 2001 and again in 2002, among 1,792 youths ages 12 to 17.

Growing Up Faster

The survey showed that watching TV with sexual content artificially aged the children: those who watched more than average behaved sexually as though they were 9 to 17 months older and watched only average amounts. Twelve-year-olds who watched the most behaved sexually like 14- and 15-year-olds who watched the least.

The research indicated that adolescents who watched shows with sexual content tended to overestimate the frequency of certain sexual behaviors and to have more permissive attitudes toward premarital sex.

As for movies, two studies that analyzed the content of top movie videos rented by young people revealed a large amount of sexual content, mostly sex among unmarried partners.

The effects of such viewing have been minimally studied. In a 2001 study of sexually active black girls ages 14 to 18, those who were exposed to X-rated movies were more likely to have multiple sexual partners, to have sex more often, to test positively for chlamydia and to be less likely to use contraception.

The music videos aimed at teenagers are rife with sexuality or eroticism, much of it explicit, the report noted. But the effects of this exposure have yet to be studied. Likewise, nothing of a scientific nature is known about the effects of magazines, advertising or video or computer games on adolescents' attitudes and behavior toward sex.

As for the Internet, one national survey of 10- to-17-year-olds found that one in five had \"inadvertently encountered explicit sexual content, and one in five had been exposed to an unwanted sexual solicitation while online.\"

The report called for better studies to assess the effects of sexuality in the mass media on adolescent beliefs and behavior, especially studies that measure over time how the cumulative effects of sexual content in different media affect teenage sexuality.

Stuart Brody, a psychologist at the University of Paisley, UK, compared the impact of different sexual activities on blood pressure when a person later experiences acute stress. For a fortnight, 24 women and 22 men kept diaries of how often they engaged in penile-vaginal intercourse (PVI), masturbation or partnered sexual activity excluding intercourse. After, the volunteers underwent a stress test involving public speaking and mental arithmetic out loud.

Volunteers who'd had PVI but none of the other kinds of sex were least stressed, and their blood pressure returned to normal faster than those who'd only masturbated or had non-coital sex. Those who abstained had the highest blood-pressure response to stress (Biological Psychology, vol 71, p 214).

Brody also made psychological measurements of neuroticism and anxiety in the volunteers, as well as work stress and partnership satisfaction. Even taking these factors into account, differences in sexual behaviour provided the best explanation for the range of stress responses. \"The effects are not attributable simply to the short-term relief afforded by orgasm, but rather, endure for at least a week,\" says Brody. He speculates that release of the \"pair-bonding\" hormone oxytocin between partners might account for the calming effect.

Pope hopes encyclical will explain true love
Wed Jan 18, 2006 7:11 AM ET

By Philip Pullella

VATICAN CITY (Reuters) - Pope Benedict said on Wednesday his long-awaited first encyclical will be published next week and that he hopes it can show Christians the proper relationship between erotic love and spiritual love.

He told pilgrims at his weekly general audience that the encyclical, called \"Deus Caritas Est\" (God is Love), will be published on January 25 to coincide with a week in which the Catholic Church prays for Christian unity.

\"In this encyclical, I want to show the concept of love in its various dimensions,\" he said, speaking without prepared remarks to make the surprise announcement.

\"In the terminology used today, love often appears very far from what a Christian thinks,\" the Pope, elected in April, told listeners in the Vatican audience hall.

The main theme of the encyclical, the highest form of papal writing, is love and charity. A pontiff's first encyclical is always keenly awaited because it is seen as a keynote for his entire papacy.

In the writing, about 50 pages long, the Pope discusses the relationship between \"eros\", or erotic love, and \"agape\", (pronounced ah-gah-pay) the Greek word referring to unconditional, spiritual and selfless love as taught by Jesus.

In his comments on Wednesday, the Pope suggested that his encyclical will warn that erotic love risked being degraded to mere sex or merchandise if it did not have a balancing component of spiritual or divine love founded on the Christian faith.

\"GIFT OF EROS\"

\"Eros, this gift of the love between a man and a woman, comes from the same source, from the goodness of creator,\" he said.

He said erotic love can be blended with and transformed into spiritual love, \"where two people really love each other and one no longer seeks his or her own joy or delights but seeks above all the good of the other person\".

The Pope told the audience he hoped his first encyclical would \"illuminate and help our Christian life\".

Vatican sources familiar with the encyclical said that in explaining his position in the encyclical, the Pope quotes not only from Biblical writings, his predecessors and Church teachings, but also from philosophers including 17th century thinker Rene Descartes.

While the Pope is believed to have written the first part himself, the second part, dedicated to the theme of charity, was already on the burner in the final years of the pontificate of his predecessor John Paul.

The second part, believed to have been written by experts and edited by the Pope, deals with the need for Christians to do charitable works.

The encyclical was due to have been published on December 8 but Vatican sources said it was delayed by a series of additions, deletions and changes after observations from various Vatican departments and cardinals who had read a draft.

Pope John Paul wrote 14 encyclicals during his nearly 27-year reign, including several so-called social encyclicals on themes such as the rights of workers and the relationship between the superpowers during the Cold War.

Pope Benedict has said he does not expect to write as much as his predecessor did but wanted to spread John Paul's teachings and see that they were properly understood.

Denis Campbell
Tuesday January 24, 2006
Observer

Whether it's the graphic intercourse in Michael Winterbottom's film Nine Songs, Eve fondling Jesus's genitals in Jerry Springer The Opera, or the recurring concern over issues such as teenage pregnancy, the subject of sex is often mired in controversy.
Bellowing headlines of the 'where will it all end' variety often suggest a country that would be more comfortable with the sexual mores of the 1950s than the 21st century. Raise the issues of prostitution, of the age of consent for gays, or of sex education and the very public debate that ensues seems to reveal that the British remain resolutely reactionary about their most intimate relations.

However, The Observer's authoritative survey this month of sexual behaviour and attitudes shows that, in a quiet revolution, Britons have become strikingly liberal over a range of key issues. Among a plethora of fascinating, revealing and sometimes contradictory findings, this significant degree of tolerance and an increasing appetite for more adventurous sex comes through strongly.

Most conspicuously, 84 per cent agree that schools should teach children about sexual behaviour and relationships - going beyond the basic biology of reproduction, the only sex-related education they are currently obliged to provide. On that issue, public opinion is far ahead of the government, which will almost certainly reject the recent call by its own independent advisers on sexual health to make such tuition mandatory.

'For years young people have told us this part of their school education is \"too little, too late and too biological\",' said Anne Weyman, head of the FPA (formerly the Family Planning Association). 'It's a big step forward to see so many adults agreeing with them at last.'

Similarly, about two-thirds (65 per cent) believe prostitution should be legalised, an increase of 4 per cent since our last survey in 2002. The number of people who have had some form of same-sex 'sexual contact' has also risen, from 11 to 15 per cent. And almost one in three people (27 per cent) has slept with someone from a different ethnic background. People from a non-white background make up 8 per cent of the UK's population.

'The survey has highlighted a definite softening of attitudes, which is heartening,' said Kaye Wellings, professor of sexual and reproductive health at the London School of Hygiene and Tropical Medicine. 'It shows that as a society we are losing our hypocrisy towards sex - thinking one thing and doing another - which has been a feature of our sexual mores in the past.

'It's better for society to have tolerant attitudes but quite constrained behaviour, rather than censorious attitudes and repressed behaviour. While Britons are becoming increasingly tolerant towards same-sex sex and paying for sex, for example, the vast majority of people are not doing the things they're quite relaxed about. That's good for the country's sexual health.'

As we become more comfortable with sex, we also appear to be more prepared to wait to have sex for the first time until we feel ready. The MORI poll reveals that the proportion of people losing their virginity before the age of consent, 16, has fallen from 32 per cent in 2002 to 20 per cent, with the number losing their virginity at age 14 or 15 dropping from 23 per cent to 15 per cent. The average age at which people have sex for the first time has actually gone up from just over 17 to nearer 18. The notion of commonplace underage sexual activity is just one of many myths that the poll dispels.

The average number of times Britons have sex every month has remained constant, at around six. There has also been a slight decrease in the number of sexual partners which the average Briton has had, from 9.6 in 2002 to 9.55. As Wellings says, the fact that most people do not have a greater number of sexual partners 'contradicts the misleading impression you get from the media of sexual hyperactivity and exoticism, the idea that there is more and more unselective, uncontrolled sexual behaviour going on'.

Fewer people had sex with someone whose name they did not know (17 per cent, down from 21), or with a work colleague (down from 31 to 28 per cent), or in order to boost their job prospects (18 per cent down to just 5), further substantiating that trend. The morals surrounding sex and faithfulness also appear to be changing. Yet as a nation we are often unconstrained - what some would call amoral - as the survey shows.

Two in five (40 per cent) have been unfaithful - 10 per cent 'frequently' or 'occasionally', despite the greater risk of detection from emails or text messages being read by the person being cheated on. The same number (39 per cent) have been involved in two overlapping sexual relationships - behaviour which experts say carries one of the greatest risks of catching herpes, chlamydia or other sexually transmitted diseases. And more Britons are having one-night stands: 53 per cent, up from 51 per cent in 2002.

Are we happy with our sex lives? Yes, according to The Observer's survey: 28 per cent declared themselves 'very satisfied' and another 34 per cent 'fairly satisfied'. As one in five (19 per cent) were 'fairly' or 'very dissatisfied', it appears that on the surface all is well.

But, as Paula Hall, a sexual psychotherapist with relationship counsellors Relate, points out: 'Add the 17 per cent who said they were \"neither satisfied nor dissatisfied\" to those 19 per cent who are unhappy, and that shows that 36 per cent of people can't say they are satisfied, which is disappointing. There's a mythology that says that everyone else is having a great sex life, which creates anxiety in people who feel they should be satisfied as much as everybody else. But a third of us aren't, which is sad.'

Hall, whose client list is drawn from that dissatisfied minority, believes 'the increased medicalisation of sex in recent years, through things like Viagra and firms offering solutions to female sexual dysfunction, has increased the pressure on people to feel they are \"good at sex\". It has made us focus more on performance rather than pleasure. It has prioritised physical fulfilment, through the number of orgasms and erections achieved, over emotional and sensual fulfilment. We have lost sight of the fact that real sexual fulfilment lies in the whole of your body and your heart and your head.'

Perhaps inevitably, our poll brought out some big differences between the sexes. Women, in general, come over as more cautious and less adventurous than men. For example, the average woman has had eight sexual partners, three fewer than men. More than a third of women wish they had waited longer before losing their virginity, but only one in seven men said the same. And 18 per cent of men compared, with 2 per cent of women, would consider paying for sex.

Asked 'After starting a new relationship, how long do you usually wait to have sex with that person?', 20 per cent of men answered either 'immediately' or 'one week', whereas 6 per cent of women gave the same answers.

Wellings said that the survey's findings will put many people at ease about their sex life. 'Despite the sexualisation of society, and the impression you get from the media about unselective and uncontrolled sexual behaviour, and the fact that we're constantly bombarded with advice about how to improve our sex lives, it's heartening that most people are still having sex six times a month with a monogamous partner,' she said. 'That may not fit with the more salacious impression the media gives, but it's actually the case, and that will be reassuring from the point of view of both our sexual health and ordinary people's expectations.'

MORI conducted the fieldwork online among 1,790 British adults aged 16-64 between 6 and 10 January. Data were weighted to reflect the national population profile.

Twentysomething

Emily Bynoe, 27, regeneration worker, London. Lives with long-term boyfriend

For me, sex is really important; it's one of the vital aspects of a relationship. I'm very relaxed about sex and, in terms of my own sex life, very open to trying new things. Even though I was brought up as a Roman Catholic, I don't link sex to guilt.

Sex is one of those things that changes when you've been with someone for a while. It means more, gets better because you know each other and becomes differently satisfying. But some of my friends who are in long-term relationships say they just don't have it any more. I think they carry on in their relationship because sex isn't that important to everyone, and people are in relationships for friendship too.

In theory, the sexual power balance between men and women has changed significantly, but not in reality. More women dress more overtly sexily than before, and some people say that's a sign of women being more in control of their bodies. They may well be, but I think we should move away from seeing women's bodies as their only playing card. We are sometimes the ones to make ourselves one-dimensional sexual creatures.

Of course women should be able to wear what they want without people making judgments about them. But with the emphasis on how everyone looks these days there's a danger that we go down a road where a woman's sexual attractiveness is seen as her most important quality. Men treat women pretty much as they always have done, and women treat men the same as they always have, except for a small minority. It's sad that so little has changed.

Fortysomething

Trish Malone, 40, former development executive in BBC Scotland drama department. Single

About 70 per cent of my female friends are in serious long-term relationships and the other 30 per cent are single, like me. The single ones really want to find a man, to be in a relationship and have all the fulfilling things that involves. They're frustrated because there aren't many decent men - interesting, available men - out there, even for very attractive women. In your twenties the pool of talent seems endless, but in your forties it's very limited indeed. Relationships are much more complicated once you hit 40. Your body clock is ticking really loudly by then, so do you want kids or not? If you want a child, does the man you're seeing want the same?

You find that a lot of attractive single women in their forties date younger men. I love the excitement of a younger guy, who may have less baggage than someone older.

Being 40 now feels very different to 10 years go. I don't feel on the shelf. There are great role models, like Madonna and Sharon Stone, who look great and are happy. I could have had children in the two long-term relationships I had in my twenties and thirties, but assume now that I won't. I'm philosophical about that.

If I met Mr Right tomorrow and we fell madly in love I could envisage trying to get pregnant, though.

Seventysomething

Alec Grieve, 72, retired GP, Glasgow. Widower and father of three

When I was growing up in the late Forties and early Fifties, you were taught that there was no sexual intercourse before marriage. You didn't expect to have sex with a girl after a date; if you were lucky, you got a bit of heavy petting. Even if you were going steady, you felt constrained not to go that final mile. The sexual climate now is different. The only sexually stimulating material available in my day was the odd magazine. Nowadays even the posh papers have sex advice columns and problem pages.

The world trivialises sex in a way that didn't happen before. Previously a sexual relationship was the culmination of a love affair. Nowadays the view often is, \"she's young, she's attractive, let's have it\" rather than \"do I like this person?\". I have been married twice, and had other relationships. I have always respected the woman involved, whether the relationship lasted just one month, a year or 28 years - like with my second wife.

By Will Boggs, MD
http://www.int.iol.co.za/index.php?set_id=1&click_id=117&art_id=qw1137740582624B243

New York - Thyroid disorders are associated with a variety of sexual
symptoms in men, according to a new report.

Dr Emmanuele A Jannini from University of L'Aquila, Italy, and associates
looked into the prevalence of sexual difficulties in 48 adult male
patients with either underactive or overactive thyroid conditions, before
and after they recovered.

Based on interviews with the 34 men with hyperthyroidism (overactive
thyroid), 18 percent had below-normal sexual desire, 3 percent had delayed
ejaculation, 50 percent had premature ejaculation, and 15 percent had
erectile dysfunction.

'Men with overactive or underactive thyroid \"must be evaluated for their
sexual function'
Among the 14 men with hypothyroidism (underactive thyroid), 64 percent had
low sexual desire, delayed ejaculation, or erectile dysfunction, while 7
percent suffered from premature ejaculation, the researchers report in the
Journal of Clinical Endocrinology & Metabolism.

When patients with hyperthyroidism were treated for the condition, the
rate of premature ejaculation fell from 50 percent to 15 percent - a
figure similar to that found in the general population, the report
indicates. Low sexual desire and delayed ejaculation resolved with
treatment in most of these patients.

Delayed ejaculation resolved in half of the hypothyroid men after
treatment, the researchers note. Erectile dysfunction almost disappeared
in these patients, and low sexual desire improved significantly.

All men with overactive or underactive thyroid \"must be evaluated for
their sexual function,\" Jannini said. He suggested that doctors ask men
three questions: 1 During the thyroid disease did your desire change? 2
Did your ability to have and to maintain the erection change? 3 Did your
ability to control ejaculation or to ejaculate change?

Reuters

They might not huddle round a marvellous mechanical mouse organ or live with an old cloth cat called Bagpuss, but scientists have discovered that mice are more musical than their simple squeaks suggest.
Research by a team of neuroscientists has revealed that male mice construct complex songs and sing them for minutes at a time when they come across sex pheromones produced by potential mates. The songs are not audible to the human ear because they are too high frequency and although scientists knew mice emitted ultrasonic chirps, recordings of the noises had never been fully analysed.

Tim Holy and Zhongsheng Guo at Washington University School of Medicine in Missouri discovered the murine melodies by accident. In experiments to test how male mice responded to sex pheromones - chemicals which are found in the urine of female mice - they recorded males as they sniffed cotton swabs dunked in urine from females, males and a mixture of the two.

\"We were trying to find out the brain mechanisms they used to detect and recognise pheromones, but we noticed the sounds they made on encountering swabs were interesting in their own right,\" said Dr Holy, whose study appears in the open access journal, Public Library of Science, Biology.

Instead of turning up their snouts, within seconds of encountering the scent of female mouse urine, the males broke into ultrasonic song. Dr Holy and his team processed the sound recordings on a computer and made them audible to the human ear, first by slowing down the entire audio track, and then by keeping the tempo but significantly lowering the pitch. \"The first moment I heard them I thought they sounded like songs, and they really do,\" said Dr Holy.

If the researchers are right, it will elevate mice to an exclusive musical club until now populated mostly by birds, whales, dolphins and gibbons.

The mice used in the experiment were genetically identical and the same age, but still the songs varied widely from mouse to mouse. Some showed a preference for certain syllables over others while others varied how long they spent on different syllables. There is no universal definition of song, but variations in the sounds made and a structure that gives the utterances rhythm make for more convincing songs, said Dr Holy. \"Instead of making sounds randomly, mice tend to repeat certain syllables a number of times, then shift to a different syllable. It sounds a lot like the twittering of a bird,\" he said.

In many bird species, song helps in mate selection, with females choosing males with the most impressive melodies.

\"We don't know for sure why mice sing, but it probably plays a part in courtship. But whether a male gains an advantage when it comes to mating by singing well is something nobody has yet looked at,\" said Dr Holy.

Because mice can easily be genetically modified to test the importance of different genes, the discovery could have a huge impact on research as diverse as the origins of speech, the causes of speech defects and the role of song.

Peter Slater, head of the bird and mammal sound communication group at St Andrews University, said: \"With birds it's really only the males that sing, so it would be good to see if that's true of mice too. It would confirm it's a sexual thing.

A Brazilian woman is suing her partner for not giving her orgasms.

According to Terra Noticias Populares reports the unnamed 31-year-old filled a complaint at Chacar Urbana Police station in Jundiai.

She complained that her 38-year-old partner reached an orgasm and then simply stopped the sexual intercourse.

Police chief Jose Roberto Ferraz is investigating the case.

Police spokesperson said: \"We will look into it, we will treat it as an ordinary complaint and let the judge decide.\"

An experimental vaccine has proved highly effective at preventing cervical cancer in a two-year study involving more than 12,000 women, researchers reported yesterday.

The vaccine works by making people immune to two types of a sexually transmitted virus that cause most cases of the disease. It is the first successful vaccine ever developed specifically to prevent cancer.

The vaccine, Gardasil, is made by Merck & Company, which plans to apply for approval to the Food and Drug Administration before the end of this year and, if the vaccine is approved, to market it in 2006.

If widely used, the vaccine could save many lives. Worldwide, there are about 500,000 new cases of cervical cancer a year, and 290,000 deaths. Most of the cases and most of the deaths occur in poorer countries where women do not have regular Pap tests, which can detect cancers or precancerous cells early enough for them to be cured. In the United States, where Pap tests are common, 10,400 new cases are expected in 2005, and 3,700 deaths.

\"The potential, particularly in the undeveloped world, particularly if they can overcome the logistics and get the vaccine to those women, could be enormous,\" said Dr. Deborah Saslow, director of breast and gynecological cancer at the American Cancer Society. The vaccine could prevent at least 70 percent of the deaths from cervical cancer, Dr. Saslow added.

But Dr. Allan Hildesheim, an epidemiologist at the National Cancer Institute, cautioned that even if women are vaccinated, they will still have to be screened regularly for cervical cancer because the vaccine does not prevent all cases of the disease.

\"This is not a panacea,\" Dr. Hildesheim said.

The vaccination will require three shots over six months. Merck has not said what it will cost.

The ideal time to vaccinate girls is before they become sexually active and risk being exposed to one of the cancer-causing viruses, said Dr. Eliav Barr, a research director at Merck. Once cancer develops, it is too late for the vaccine to help. The median age at which girls first have sex in the United States is 15.

It is not known yet how long the protection from the vaccine will last, or whether booster shots will be necessary, Dr. Barr said.

The vaccine works against viruses that belong to a group called human papillomaviruses, or HPV. Nearly every case of cervical cancer is caused by HPV. The viruses are sexually transmitted, extremely common and almost impossible to avoid. At least half the adults in the United States have been infected.

More than 30 types of HPV infect the human genital area. Only some types cause cancer; others cause genital warts. A type known as HPV-16 causes 50 percent of cervical cancers, and HPV-18 causes 20 percent. Other types cause the rest. But even the cancer-causing types are harmless in most people because their immune systems fight them off.

The virus persists in some women, however, causing abnormal growths on the cervix. Most of the growths go away, but some turn cancerous.

Gardasil protects against HPV 16 and 18, which together cause 70 percent of cervical cancers. It is also designed to prevent infection with two other virus types, 6 and 11, which cause 90 percent of cases of genital warts. The four virus types can cause non-cancerous cervical growths that lead to nerve-racking false alarms on Pap tests, and the vaccine is expected to spare many women the abnormal test results.

Merck scientists were scheduled to present the results of the two-year study today at an infectious disease conference in San Francisco.

Their test group included more than 12,000 women, ages 16 to 26, from 13 countries. Half got Gardasil and half placebos.

Among the women who received all three doses of vaccine and did not have HPV infection when they started the study, the researchers found no precancerous cells or early cervical cancers associated with HPV 16 or 18. But among those who got placebos, there were 21 cases.

The findings mean the vaccine was 100 percent effective at preventing the cancers caused by types 16 and 18. But some women in the vaccinated group did develop precancerous cells caused by other HPV types; the company did not disclose how many.

The vaccine is made up of proteins that are normally found on the outer shell of HPV. The proteins, called viruslike particles, are produced by yeasts that have been spliced with viral genes. They provoke a strong immune response that can then prevent infection.

Although Merck will first seek permission to vaccinate girls and women, the company plans eventually to seek approval to use Gardasil in boys and men as well. The company hopes the vaccine will appeal to men because it may prevent genital warts, which can turn into large, ugly growths on the penis.

Vaccinating men might protect their sexual partners as well, including not just women but men who have sex with men, a group at risk for anal cancer caused by HPV. However, Merck has not disclosed any data on whether the vaccine works in men.

Another drug maker, GlaxoSmithKline, is also working on a cervical cancer vaccine, one that does not include wart protection. The company did not respond to several telephone requests for information on the status of its vaccine.

By LUKAS I. ALPERT

Sex in the city is as hot as ever.

Nearly one-quarter of New York City women say they're doing the deed several times a week, according to a new survey, far outstripping the competition.

Twenty-three percent of Big Apple gals say they're regularly steaming up the sheets, compared with 18 percent of women in Los Angeles, and 17 percent in Dallas, Miami and Chicago, the Trojan Survey of Women and Desire found.

But don't expect to see the city's nickname changed from the Big Apple to the Big Ohh anytime soon — only 22 percent say they have an orgasm during sex.

The survey found that as far as sex is concerned, New York is the safest city in the country, with 93 percent of respondents saying they use condoms the first time they get down with a new partner. By comparison, it's 87 percent in L.A. and 85 percent in both Dallas and Chicago. But New York women are willing to take more chances in some regard, with 68 percent admitting they have had a sex partner whom they don't consider \"relationship material,\" but whom they consider \"thrilling\" anyway. Only 58 percent said the same in the rest of the country.

Big Apple feminine sexuality was more on par with the rest of the nation in several areas, though. Both in New York and across the country, 42 percent of respondents said they considered themselves \"very sexually confident.\"

And while 72 percent of women in other parts of the country said experimentation was an important part of sexual fulfillment, only 68 percent of Gotham babes thought so.

And most still want guys to make the first move, though barely so. While 96 percent of women say they love it when men approach them, 51 percent say they never turn the tables and approach a man, according to separate survey done by the global dating service It's Just Lunch.

Trojan's nationwide online survey of 1,639 woman, ranging in age from 18 to 59, was conducted as part of a marketing push for its soon-to-be released Elexa — a line of sexual health products geared toward women.

\"Despite regional differences, women across America believe that good sex is a must-have as part of a healthy and fulfilling relationship,\" said Cassandra Johnson, Trojan's product manager for Elexa.

New York Times, Health

Josh was a man in his 40's I'd been treating for depression. His wife had given birth to their first child, a girl, three days before.

\"Congratulations,\" I said.

\"She's beautiful. A miracle,\" he responded.

\"Amazing, isn't it?\" I agreed, remembering the first time I held my own daughter.

\"Just incredible.\" He shrugged, shook his head. His foot started tapping. \"You were ... there?\" he asked me, tentatively. \"I mean, for the delivery?\"

There. I could hear the other questions coming. I have heard them many times from men whose wives had given birth days or weeks before our sessions.

Even when I had been treating these men for a year or more, they always seemed uncharacteristically hesitant to broach this topic.

\"I was,\" I said. I waited.

He nodded. \"Incredible, isn't it?\"

\"It's a lot of things,\" I said, giving him permission to say more.

He relaxed a bit. The tapping of his foot slowed. \"Where were you? The head of the bed?\"

That was almost always the next question. \"Just about the whole time,\" I said.

He winced. \"I probably should have stayed up there, too.\"

\"Why's that?\"

\"You know,\" he said with a smile.

He couldn't bear to say it. \"You saw more than you wanted to?\" I asked.

The smile left his face. \"I just can't get it out of my mind.\"

\"What about it?\"

\"Nothing.\"

I waited.

\"I mean,\" he went on, \"how are you supposed to go from seeing that to wanting to be with ... ?\" He stopped, but his eyes kept asking the question.

\"Right,\" I said. \"It gets easier with time, for just about everyone.\"

Although no one seems to talk publicly about the problem, Josh is only one of dozens of men who have confided to me that witnessing the births of their children has made it difficult for them to be attracted to their wives, at least in the short run.

They seem to have trouble seeing them as sexual beings after seeing them make babies, trouble reverting to a mind-set in which their wives' sexual anatomy is just that - not associated with images of new life emerging through the birth canal.

In the age of the \"new man,\" very little consideration is given to the potentially negative side effects of togetherness in the delivery room. Every man I have spoken with over the past few years knows he is expected to be with his wife when his child comes into the world.

How can anyone explain sitting out such a life-changing moment in the waiting room?

The trouble is that the moment turns out to be both intensely beautiful and potentially traumatic.

It is miraculous to see a baby's head emerge, and it can also be shocking. It is riveting to see an umbilical cord connecting mother and baby, but it can also be very disturbing. It is exciting to be asked by a doctor to cut that umbilical cord, but also potentially very frightening, even for otherwise rather fearless men.

And not every man gets over it. Several men have confessed to me that they never regained the same romantic view of their wives that they had before seeing them deliver children.

\"They ended up having to cut her open to get the baby,\" one patient told me. \"I saw it. I mean, how am I supposed to get that out of my head? Every time I look at the scar, it's like I'm seeing it again.\"

In the most striking cases, the symptoms that men experience come close to post-traumatic stress disorder, with its roots in the witnessing of an event that involves a threat to the physical integrity of self or others and responding with intense fear, helplessness or horror.

The symptoms, as my patients have reported, include recurrent and intrusive distressing recollections of the event and efforts to avoid recalling it.

I do not believe that most men suffer these symptoms. But some do. And predicting which men will be vulnerable to them is nearly impossible in a social climate in which men who admit reticence about being present in the delivery room risk being labeled throwbacks.

The fact that the subject is taboo also means that a man who is traumatized by the experience may be retraumatized again and again, with each child born to him.

\"Honestly,\" one man, married for 12 years, told me, \"I think one of the main reasons I don't feel attracted to my wife is that I saw her give birth three times. It's like I know too much about that part of her.\"

The mystery is gone. And while there are other contributing factors to the loss of passion in the man's marriage, one of them does seem to be his presence in the delivery room, three times.

And I'm not sure that the delivery is the only cause of men's psychological struggles during their partners' pregnancies.

I myself recall feeling as if the clinical focus on childbirth during prenatal classes, including the detailed descriptions of the placenta and the meconium, took away from the wonder of the process, rather than adding to it.

I don't know what is gained by showing the cross-sectional anatomy of a woman's torso to her lover.

Whether the father is present in the delivery room is a couple's personal decision, of course.

But it is a decision that involves potential gains and potential losses, and too few couples realize that fact or are willing to talk about it.

Women may want to consider the risks as they invite their partners to watch them bring new life into the world. For some of the passion that binds them together may leave their lives at the very same time.

(Reuters Health)

NEW YORK (Reuters Health) - Prostate cancer developed in 20 men within months to a few years after they began testosterone supplementation to correct a deficiency of the hormone, investigators report.

\"There are several anecdotal case reports, small studies, and observational studies like ours which raise concern but do not provide conclusive evidence yet,\" Dr. Franklin D. Gaylis told Reuters Health.

The issue is a concern because prostate cancer is usually driven by testosterone.

Gaylis, from the University of California at San Diego Medical Center, and colleagues report this series of patients \"in whom clinically significant prostate cancer developed and was presumed to be related to exogenous testosterone use,\" in the Journal of Urology.

The men were identified in six different urology practices. Prostate cancer was detected within 2 years of the start of testosterone replacement in 11 of these men, seven of them within the first year, the authors report. The others were diagnosed after 28 months to 8 years.

Eleven men had normal prostate exams before testosterone supplementation was begun, the report indicates, and the average PSA level of the 17 men tested before treatment was 3, although the range was 0.9 to 15. The threshold for further evaluation is usually 4.

\"It is our belief that men, especially those with a family history of prostate cancer, should not receive a prescription for testosterone supplementation without careful, informed consultation regarding the risks and benefits of such treatment,\" the investigators conclude.

\"I would hope that guidelines would be developed by experts in the field to help us appropriately and carefully prescribe testosterone replacement to men who clearly need it and who would benefit from it, and then monitor them for potential adverse outcomes, e.g., the development of prostate cancer,\" Gaylis said.

While the study has flaws, writes Dr. E. Darracott Vaughan, Jr. from Weill Medical College of Cornell University, New York, in a related editorial, it \"can be taken as a 'shot across the bow' for urologists and other physicians. We need to be extremely careful before beginning testosterone therapy.\"

SOURCE: Journal of Urology, August 2005.

By Neil Swidey, August 14, 2005, Boston Globe

With crystal-blue eyes, wavy hair, and freshly scrubbed faces, the boys look as though they stepped out of a Pottery Barn Kids catalog. They are 7-year-old twins. I'll call them Thomas and Patrick; their parents agreed to let me meet the boys as long as I didn't use their real names.

Spend five seconds with them, and there can be no doubt that they are identical twins - so identical even they can't tell each other apart in photographs. Spend five minutes with them, and their profound differences begin to emerge.

Patrick is social, thoughtful, attentive. He repeatedly addresses me by name. Thomas is physical, spontaneous, a bit distracted. Just minutes after meeting me outside a coffee shop, he punches me in the upper arm, yells, \"Gray punch buggy!\" and then points to a Volkswagen Beetle cruising past us. It's a hard punch. They horse around like typical brothers, but Patrick's punches are less forceful and his voice is higher. Thomas charges at his brother, arms flexed in front of him like a mini-bodybuilder. The differences are subtle - they're 7-year-old boys, after all - but they are there.

When the twins were 2, Patrick found his mother's shoes. He liked wearing them. Thomas tried on his father's once but didn't see the point.

When they were 3, Thomas blurted out that toy guns were his favorite things. Patrick piped up that his were the Barbie dolls he discovered at day care.

When the twins were 5, Thomas announced he was going to be a monster for Halloween. Patrick said he was going to be a princess. Thomas said he couldn't do that, because other kids would laugh at him. Patrick seemed puzzled. \"Then I'll be Batman,\" he said.

Their mother - intelligent, warm, and open-minded - found herself conflicted. She wanted Patrick - whose playmates have always been girls, never boys - to be himself, but she worried his feminine behavior would expose him to ridicule and pain. She decided to allow him free expression at home while setting some limits in public.

That worked until last year, when a school official called to say Patrick was making his classmates uncomfortable. He kept insisting that he was a girl.

Patrick exhibits behavior called childhood gender nonconformity, or CGN. This doesn't describe a boy who has a doll somewhere in his toy collection or tried on his sister's Snow White outfit once, but rather one who consistently exhibits a host of strongly feminine traits and interests while avoiding boy-typical behavior like rough-and-tumble play. There's been considerable research into this phenomenon, particularly in males, including a study that followed boys from an early age into early adulthood. The data suggest there is a very good chance Patrick will grow up to be homosexual. Not all homosexual men show this extremely feminine behavior as young boys. But the research indicates that, of the boys who do exhibit CGN, about 75 percent of them - perhaps more - turn out to be gay or bisexual.

What makes the case of Patrick and Thomas so fascinating is that it calls into question both of the dominant theories in the long-running debate over what makes people gay: nature or nurture, genes or learned behavior. As identical twins, Patrick and Thomas began as genetic clones. From the moment they came out of their mother's womb, their environment was about as close to identical as possible - being fed, changed, and plopped into their car seats the same way, having similar relationships with the same nurturing father and mother. Yet before either boy could talk, one showed highly feminine traits while the other appeared to be \"all boy,\" as the moms at the playgrounds say with apologetic shrugs.

\"That my sons were different the second they were born, there is no question about it,\" says the twins' mother.

So what happened between their identical genetic starting point and their births? They spent nine months in utero. In the hunt for what causes people to be gay or straight, that's now the most interesting and potentially enlightening frontier.

WHAT DOES IT MATTER WHERE HOMOSEXUALITY COMES FROM? Proving people are born gay would give them wider social acceptance and better protection against discrimination, many gay rights advocates argue. In the last decade, as this \"biological\" argument has gained momentum, polls find Americans - especially young adults - increasingly tolerant of gays and lesbians. And that's exactly what has groups opposed to homosexuality so concerned. The Family Research Council, a conservative Christian think tank in Washington, D.C., argues in its book Getting It Straight that finding people are born gay \"would advance the idea that sexual orientation is an innate characteristic, like race; that homosexuals, like African-Americans, should be legally protected against 'discrimination;' and that disapproval of homosexuality should be as socially stigmatized as racism. However, it is not true.\"

Some advocates of gay marriage argue that proving sexual orientation is inborn would make it easier to frame the debate as simply a matter of civil rights. That could be true, but then again, freedom of religion enjoyed federal protection long before inborn traits like race and sex.

For much of the 20th century, the dominant thinking connected homosexuality to upbringing. Freud, for instance, speculated that overprotective mothers and distant fathers helped make boys gay. It took the American Psychiatric Association until 1973 to remove \"homosexuality\" from its manual of mental disorders.

Then, in 1991, a neuroscientist in San Diego named Simon LeVay told the world he had found a key difference between the brains of homosexual and heterosexual men he studied. LeVay showed that a tiny clump of neurons of the anterior hypothalamus - which is believed to control sexual behavior - was, on average, more than twice the size in heterosexual men as in homosexual men. LeVay's findings did not speak directly to the nature-vs.-nurture debate - the clumps could, theoretically, have changed size because of homosexual behavior. But that seemed unlikely, and the study ended up jump-starting the effort to prove a biological basis for homosexuality.

Later that same year, Boston University psychiatrist Richard Pillard and Northwestern University psychologist J. Michael Bailey announced the results of their study of male twins. They found that, in identical twins, if one twin was gay, the other had about a 50 percent chance of also being gay. For fraternal twins, the rate was about 20 percent. Because identical twins share their entire genetic makeup while fraternal twins share about half, genes were believed to explain the difference. Most reputable studies find the rate of homosexuality in the general population to be 2 to 4 percent, rather than the popular \"1 in 10\" estimate.

In 1993 came the biggest news: Dean Hamer's discovery of the \"gay gene.\" In fact, Hamer, a Harvard-trained researcher at the National Cancer Institute, hadn't quite put it that boldly or imprecisely. He found that gay brothers shared a specific region of the X chromosome, called Xq28, at a higher rate than gay men shared with their straight brothers. Hamer and others suggested this finding would eventually transform our understanding of sexual orientation.

That hasn't happened yet. But the clear focus of sexual-orientation research has shifted to biological causes, and there hasn't been much science produced to support the old theories tying homosexuality to upbringing. Freud may have been seeing the effect rather than the cause, since a father faced with a very feminine son might well become more distant or hostile, leading the boy's mother to become more protective. In recent years, researchers who suspect that homosexuality is inborn - whether because of genetics or events happening in the womb - have looked everywhere for clues: Prenatal hormones. Birth order. Finger length. Fingerprints. Stress. Sweat. Eye blinks. Spatial relations. Hearing. Handedness. Even \"gay\" sheep.

LeVay, who is gay, says that when he published his study 14 years ago, some gays and lesbians criticized him for doing research that might lead to homosexuality once again being lumped in with diseases and disorders. \"If anything, the reverse has happened,\" says LeVay, who is now 61 and no longer active in the lab. He says the hunt for a biological basis for homosexuality, which involves many researchers who are themselves gay or lesbian, \"has contributed to the status of gay people in society.\"

These studies have been small and underfunded, and the results have often been modest. Still, because there's been so much of this disparate research, \"all sort of pointing in the same direction, makes it pretty clear there are biological processes significantly influencing sexual orientation,\" says LeVay. \"But it's also kind of frustrating that it's still a bunch of hints, that nothing is really as crystal clear as you would like.\"

Just in the last few months, though, the hints have grown stronger.

In May, Swedish researchers reported finding important differences in how the brains of straight men and gay men responded to two compounds suspected of being pheromones - those scent-related chemicals that are key to sexual arousal in animals. The first compound came from women's urine, the second from male sweat. Brain scans showed that when straight men smelled the female urine compound, their hypothalamus lit up. That didn't happen with gay men. Instead, their hypothalamus lit up when they smelled the male-sweat compound, which was the same way straight women had responded. This research once again connecting the hypothalamus to sexual orientation comes on the heels of work with sheep. About 8 percent of domestic rams are exclusively interested in sex with other rams. Researchers found that a clump of neurons similar to the one LeVay identified in human brains was also smaller in gay rams than straight ones. (Again, it's conceivable that these differences could be showing effect rather than cause.)

In June, scientists in Vienna announced that they had isolated a master genetic switch for sexual orientation in the fruit fly. Once they flicked the switch, the genetically altered female flies rebuffed overtures from males and instead attempted to mate with other females, adopting the elaborate courting dance and mating songs that males use.

And now, a large-scale, five-year genetic study of gay brothers is underway in North America. The study received $2.5 million from the National Institutes of Health, which is unusual. Government funders tend to steer clear of sexual orientation research, aware that even small grants are apt to be met with outrage from conservative congressmen looking to make the most of their C-Span face time. Relying on a robust sample of 1,000 gay-brother pairs and the latest advancements in genetic screening, this study promises to bring some clarity to the murky area of what role genes may play in homosexuality.

This accumulating biological evidence, combined with the prospect of more on the horizon, is having an effect. Last month, the Rev. Rob Schenck, a prominent Washington, D.C., evangelical leader, told a large gathering of young evangelicals that he believes homosexuality is not a choice but rather a predisposition, something \"deeply rooted\" in people. Schenck told me that his conversion came about after he'd spoken extensively with genetic researchers and psychologists. He argues that evangelicals should continue to oppose homosexual behavior, but that \"many evangelicals are living in a sort of state of denial about the advance of this conversation.\" His message: \"If it's inevitable that this scientific evidence is coming, we have to be prepared with a loving response. If we don't have one, we won't have any credibility.\"

AS THE 21-YEAR-OLD COLLEGE JUNIOR IN A HOSPITAL JOHNNY slides into the MRI, she is handed controls with buttons for \"strongly like\" and \"strongly dislike.\" Hundreds of pornographic images - in male-male and female-female pairings - flash before her eyes. Eroticism eventually gives way to monotony, and it's hard to avoid looking for details to distinguish one image from the rest of the panting pack. So it goes from \"Look at the size of those breasts!\" to \"That can't be comfortable, given the length of her fingernails!\" to \"Why is that guy wearing nothing but work boots on the beach?\"

Regardless of which buttons the student presses, the MRI scans show her arousal level to each image, at its starting point in the brain.

Researchers at Northwestern University, outside Chicago, are doing this work as a follow-up to their studies of arousal using genital measurement tools. They found that while straight men were aroused by film clips of two women having sex, and gay men were aroused by clips of two men having sex, most of the men who identified themselves as bisexual showed gay arousal patterns. More surprising was just how different the story with women turned out to be. Most women, whether they identified as straight, lesbian, or bisexual, were significantly aroused by straight, gay, and lesbian sex. \"I'm not suggesting that most women are bisexual,\" says Michael Bailey, the psychology professor whose lab conducted the studies. \"I'm suggesting that whatever a woman's sexual arousal pattern is, it has little to do with her sexual orientation.\" That's fundamentally different from men. \"In men, arousal is orientation. It's as simple as that. That's how gay men learn they are gay.\"

These studies mark a return to basics for the 47-year-old Bailey. He says researchers need a far deeper understanding of what sexual orientation is before they can determine where it comes from.

Female sexual orientation is particularly foggy, he says, because there's been so little research done. As for male sexual orientation, he argues that there's now enough evidence to suggest it is \"entirely in-born,\" though not nearly enough to establish how that happens.

Bailey's 1991 twin study is still cited by other researchers as one of the pillars in the genetic argument for homosexuality. But his follow-up study using a comprehensive registry of twins in Australia found a much lower rate of similarity in sexual orientation between identical twins, about 20 percent, down from 50 percent. Bailey still believes that genes make important contributions to sexual orientation. But, he says, \"that's not where I'd bet the real breakthroughs will come.\"

His hunch is that further study of childhood gender nonconformity will pay big. Because it's unclear what percentage of homosexuals and lesbians showed CGN as children, Bailey and his colleagues are now running a study that uses adult participants' home movies from childhood to look for signs of gender-bending behavior.

Cornell psychologist Daryl Bem has proposed an intriguing theory for how CGN might lead to homosexuality. According to this pathway, which he calls \"the exotic becomes erotic,\" children are born with traits for temperament, such as aggression and activity level, that predispose them to male-typical or female-typical activities. They seek out playmates with the same interests. So a boy whose traits lead him to hopscotch and away from rough play will feel different from, and ostracized by, other boys. This leads to physiological arousal of fear and anger in their presence, arousal that eventually is transformed from exotic to erotic.

Critics of homosexuality have used Bem's theory, which stresses environment over biology, to argue that sexual orientation is not inborn and not fixed. But Bem says this pathway is triggered by biological traits, and he doesn't really see how the outcome of homosexuality can be changed.

Bailey says whether or not Bem's theory holds up, the environment most worth focusing in on is the one a child experiences when he's in his mother's womb.

LET'S GET BACK TO THOMAS AND PATRICK. BECAUSE IT'S UNCLEAR why twin brothers with identical genetic starting points and similar post-birth environments would take such divergent paths, it's helpful to return to the beginning.

Males and females have a fundamental genetic difference - females have two X chromosomes, and males have an X and a Y. Still, right after conception, it's hard to tell male and female zygotes apart, except for that tucked-away chromosomal difference. Normally, the changes take shape at a key point of fetal development, when the male brain is masculinized by sex hormones. The female brain is the default. The brain will stay on the female path as long as it is protected from exposure to hormones. The hormonal theory of homosexuality holds that, just as exposure to circulating sex hormones determines whether a fetus will be male or female, such exposure must also influence sexual orientation.

The cases of children born with disorders of \"sexual differentiation\" offer insight. William Reiner, a psychiatrist and urologist with the University of Oklahoma, has evaluated more than a hundred of these cases. For decades, the standard medical response to boys born with severely inadequate penises (or none at all) was to castrate the boy and have his parents raise him as a girl. But Reiner has found that nurture - even when it involves surgery soon after birth - cannot trump nature. Of the boys with inadequate penises who were raised as girls, he says, \"I haven't found one who is sexually attracted to males.\" The majority of them have transitioned back to being males and report being attracted to females.

During fetal development, sexual identity is set before the sexual organs are formed, Reiner says. Perhaps it's the same for sexual orientation. In his research, of all the babies with X and Y chromosomes who were raised as girls, the only ones he has found who report having female identities and being attracted to males are those who did not have \"receptors\" to let the male sex hormones do their masculinizing in the womb.

What does this all mean? \"Exposure to male hormones in utero dramatically raises the chances of being sexually attracted to females,\" Reiner says. \"We can infer that the absence of male hormone exposure may have something to do with attraction to males.\"

Michael Bailey says Reiner's findings represent a major breakthrough, showing that \"whatever causes sexual orientation is strongly influenced by prenatal biology.\" Bailey and Reiner say the answer is probably not as simple as just exposure to sex hormones. After all, the exposure levels in some of the people Reiner studies are abnormal enough to produce huge differences in sexual organs. Yet, sexual organs in straight and gay people are, on average, the same. More likely, hormones are interacting with other factors.

Canadian researchers have consistently documented a \"big-brother effect,\" finding that the chances of a boy being gay increase with each additional older brother he has. (Birth order does not appear to play a role with lesbians.) So, a male with three older brothers is three times more likely to be gay than one with no older brothers, though there's still a better than 90 percent chance he will be straight. They argue that this results from a complex interaction involving hormones, antigens, and the mother's immune system.

By now, there is substantial evidence showing correlation - though not causation - between sexual orientation and traits that are set when a baby is in the womb. Take finger length. In general, men have shorter index fingers in relation to their ring fingers; in women, the lengths are generally about the same. Researchers have found that lesbians generally have ratios closer to males. Other studies have shown masculinized results for lesbians in inner-ear functions and eye-blink reactions to sudden loud noises, and feminized patterns for gay men on certain cognitive tasks like spatial perception and remembering the placement of objects.

New York University researcher Lynn S. Hall, who has studied traits determined in the womb, speculates that Patrick was somehow prenatally stressed, probably during the first trimester, when the brain is really developing, particularly the structures like the hypothalamus that influence sexual behavior. This stress might have been based on his position in the womb or the blood flow to him or any of a number of other factors not in his mother's control. Yet more evidence that identical twins have womb experiences far from identical can be found in their often differing birth weights. Patrick was born a pound lighter than Thomas.

Taken together, the research suggests that early on in the womb, as the fetus's brain develops in either the male or female direction, something fundamental to sexual orientation is happening. Nobody's sure what's causing it. But here's where genes may be involved, perhaps by regulating hormone exposure or by dictating the size of that key clump of neurons in the hypothalamus. Before researchers can sort that out, they'll need to return to the question of whether, in fact, there is a \"gay gene.\"

THE CROWD ON BOSTON COMMON IS THICK ON THIS SCORCHER of a Saturday afternoon in June, as the throngs make their way around the 35th annual Boston Pride festival, past booths peddling everything from \"Gayopoly\" board games to Braveheartian garments called Utilikilts. Sitting quietly in his booth is Alan Sanders, a soft-spoken 41-year-old with a sandy beard and thinning hair. He's placeda mound of rainbow-colored Starbursts on the table in front of him and hung a banner that reads: \"WANTED: Gay Men with Gay Brothers for Molecular Genetic Study of Sexual Orientation.\"

Sanders is a psychiatrist with the Evanston Northwestern Healthcare Research Institute who is leading the NIH-funded search for the genetic basis of male homosexuality (www.gaybros.com). He is spending the summer crisscrossing the country, going to gay pride festivals, hoping to recruit 1,000 pairs of gay brothers to participate. (His wife, who just delivered their third son, wasn't crazy about the timing.) When people in Boston ask him how much genes may contribute to homosexuality, he says the best estimate is about 40 percent.

Homosexuality runs in families - studies show that 8 to 12 percent of brothers of gay men are also gay, compared with the 2 to 4 percent of the general population.

Sanders spends much of the afternoon handing out Starbursts to people who clearly don't qualify for a gay brothers study - preteen girls, adult lesbians wearing T-shirts that read \"I Like Girls Who Like Girls,\" and elderly women in straw hats who speak only Chinese. But many of the gay men who stop by are interested in more than free candy. Among the people signing up is James Daly, a 31-year-old from Salem. \"I think it's important for the public - especially the religious right - to know it's not a choice for some people,\" Daly says. \"I feel I was born this way.\"

(In fairness, there aren't many leaders of groups representing social and religious conservatives who still argue that homosexual orientation - as opposed to behavior - is a matter of choice. Even as he insists that no one is born gay, Peter Sprigg, the point person on homosexuality for the Family Research Council, says, \"I don't think that people choose their sexual attraction.\")

In the decade since Dean Hamer made headlines, the gay gene theory has taken some hits. A Canadian team was unable to replicate his findings. Earlier this year, a team from Hamer's own lab reported only mixed results after having done the first scan of the entire human genome in the search for genes influencing sexual orientation.

But all of the gene studies so far have been based on small samples and lacked the funding to do things right. Sanders's study should be big enough to provide some real answers on linkage as well as shed light on gender nonconformity and the big-brother effect.

There is, however, a towering question that Sanders's study will probably not be able to answer. That has to do with evolution. If a prime motivation of all species is to pass genes on to future generations, and gay men are estimated to produce 80 percent fewer offspring than straight men, why would a gay gene not have been wiped out by the forces of natural selection? This evolutionary disadvantage is what led former Amherst College biologist Paul Ewald to argue that homosexuality might be caused by a virus - a pathogen most likely working in utero. That argument caused a stir when he and a colleague proposed it six years ago, but with no research done to test it, it remains just another theory. Other scientists have offered fascinating but unpersuasive explanations, most of them focusing on some kind of compensatory benefit, in the same way that the gene responsible for sickle cell anemia also protects against malaria. A study last year by researchers in Italy showed that female relatives of gay men tended to be more fertile, though, as critics point out, not nearly fertile enough to make up for the gay man's lack of offspring.

But there will be plenty of time for sorting out the evolutionary paradox once - and if - researchers are able to identify actual genes involved in sexual orientation. Getting to that point will likely require integrating multiple lines of promising research. That is exactly what's happening in Eric Vilain's lab at the University of California, Los Angeles. Vilain, an associate professor of human genetics, and his colleague, Sven Bocklandt, are using gay sheep, transgenic mice, identical twin humans, and novel approaches to human genetics to try to unlock the mystery of sexual orientation.

Instead of looking for a gay gene, they stress that they are looking for several genes that cause either attraction to men or attraction to women. Those same genes would work one way in heterosexual women and another way in homosexual men. The UCLA lab is examining how these genes might be turned \"up\" or \"down.\" It's not a question of what genes you have, but rather which ones you use, says Bocklandt. \"I have the genes in my body to make a vagina and carry a baby, but I don't use them, because I am a man.\" In studying the genes of gay sheep, for example, he's found some that are turned \"way up\" compared with the straight rams.

The lab is also testing an intriguing theory involving imprinted genes. Normally, we have two copies of every gene, one from each parent, and both copies work. They're identical, so it doesn't matter which copy comes from which parent. But with imprinted genes, that does matter. Although both copies are physically there, one copy - either from the mom or the dad - is blocked from working. Think of an airplane with an engine on each wing, except one of the engines is shut down. A recent Duke University study suggests humans have hundreds of imprinted genes, including one on the X chromosome that previous research has tied to sexual orientation.

With imprinted genes, there is no backup engine. So if there's something atypical in the copy from mom, the copy from dad cannot be turned on. The UCLA lab is now collecting DNA from identical twins in which one twin is straight and the other is gay. Because the twins begin as genetic clones, if a gene is imprinted in one twin, it will be in the other twin as well. Normally, as the fetuses are developing, each time a cell divides, the DNA separates and makes a copy of itself, replicating all kinds of genetic information. It's a complicated but incredibly accurate process. But the coding to keep the backup engine shut down on an imprinted gene is less accurate.

So how might imprinted genes help explain why one identical twin would be straight and the other gay? Say there's an imprinted gene for attraction to females, and there's something atypical in the copy the twin brothers get from mom. As all that replicating is going on, the imprinting (to keep the copy from dad shut down) proceeds as expected in one twin, and he ends up gay. But somehow with his brother, the coding for the imprinting is lost, and rather than remain shut down, the fuel flows to fire up the backup engine from dad. And that twin turns out to be straight.

IN THE COURSE OF REPORTING THIS STORY, I EXPERIENCED A good deal of whiplash. Just when I would become swayed by the evidence supporting one discreet theory, I would stumble onto new evidence casting some doubt on it. Ultimately, I accepted this as unavoidable terrain in the hunt for the basis of sexual orientation. This is, after all, a research field built on underfunded, idiosyncratic studies that are met with full-barreled responses from opposing and well-funded advocacy groups determined to make the results from the lab hew to the scripts they've honed for the talk-show circuit.

You can't really blame the advocacy groups. The stakes are high. In the end, homosexuality remains such a divisive issue that only thoroughly tested research will get society to accept what science has to say about its origin. Critics of funding for sexual orientation research say that it isn't curing cancer, and they're right. But we devote a lot more dollars to studying other issues that aren't curing cancer and have less resonance in society.

Still, no matter how imperfect these studies are, when you put them all together and examine them closely, the message is clear: While post-birth development may well play a supporting role, the roots of homosexuality, at least in men, appear to be in place by the time a child is born. After spending years sifting through all the available data, British researchers Glenn Wilson and Qazi Rahman come to an even bolder conclusion in their forthcoming book Born Gay: The Psychobiology of Sex Orientation, in which they write: \"Sexual orientation is something we are born with and not `acquired' from our social environment.\"

Meanwhile, the mother of twins Patrick and Thomas has done her own sifting and come to her own conclusions. She says her son's feminine behavior suggests he will grow up to be gay, and she has no problem with that. She just worries about what happens to him between now and then.

After that fateful call from Patrick's school, she says, \"I knew I had to talk to my son, and I had no clue what to say.\" Ultimately, she told him that although he could play however he wanted at home, he couldn't tell his classmates he was a girl, because they'd think he was lying. And she told him that some older boys might be mean to him and even hit him if he continued to claim he was a girl.

Then she asked him, \"Do you think that you can convince yourself that you are a boy?\"

\"Yes, Mom,\" he said. \"It's going to be like when I was trying to learn to read, and then one day I opened the book and I could read.\"

His mother's heart sank. She could tell that he wanted more than anything to please her. \"Basically, he was saying there must be a miracle - that one day I wake up and I'm a boy. That's the only way he could imagine it could happen.\"

In the year since that conversation, Patrick's behavior has become somewhat less feminine. His mother hopes it's just because his interests are evolving and not because he's suppressing them.

\"I can now imagine him being completely straight, which I couldn't a year ago,\" she says. \"I can imagine him being gay, which seems to be statistically most likely.\"

She says she's fine with either outcome, just as long as he's happy and free from harm. She takes heart in how much more accepting today's society is. \"By the time my boys are 20, the world will have changed even more.\"

By then, there might even be enough concensus for researchers to forget about finger lengths and fruit flies and gay sheep, and move on to a new mystery.

Neil Swidey is a member of the Globe Magazine staff. He can be reached at swidey@globe.com.

© Copyright 2005 The New York Times Company
http://www.boston.com/news/globe/magazine/articles/2005/08/14/what_makes_people_gay/

A scientist set out to prove an old adage of pop psychology: men will
overcompensate by acting excessively \"manly\" when their masculinity is
threatened. But to do it, he had to play mind tricks on some unsuspecting men.

It seems he got what he wanted.

Men in his study were found to profess greater support of the Iraq war if they
were told that their recent responses on a questionnaire marked them as
\"feminine\" types. 

What they weren't told was that this information about their masculinity had no
factual basis.

These men also voiced more anti-gay attitudes and greater willingness to buy a
big car than other men, according to the researcher, Robb Willer, a sociology
doctoral candidate at Cornell University in Ithaca, N.Y.

\"If you made men more insecure about their masculinity, they displayed more
homophobic attitudes, tended to support the Iraq War more and would be more
willing to purchase an SUV [sport utility vehicle],\" Willer said.

Willer added that he plans to present his findings Aug. 15 at the American
Sociological Association's 100th annual meeting in Philadelphia.

\"Masculine overcompensation is the idea that men who are insecure about their
masculinity will behave in an extremely masculine way as compensation,\" Willer
explained. \"I wanted to test this idea and also explore whether overcompensation
could help explain some attitudes like support for war and animosity to
homosexuals.\"

Willer administered a gender identity survey to a sample of male and female
Cornell undergraduates in the fall of 2004. Participants were randomly assigned
to receive feedback that their responses indicated either a masculine or a
feminine identity. While women's responses were unchanged regardless of the
feedback they received, men's reactions \"were strongly affected by this
feedback,\" Willer said.

\"Masculinity-threatened men also reported feeling more ashamed, guilty, upset
and hostile than did masculinity-confirmed men,\" said Willer in a report on his
findings.

The notion that masculinity-threatened men overcompensate is rooted in the
theories of Sigmund Freud, the 19th-and early-20th century psychologist. The
idea has become a common part of household wisdom, though, with the more
pro-women's-rights culture that has established itself in the the last few
decades in Western societies.

Nonetheless, the idea still hasn't been properly tested, Willer said. He
conducted a test with 111 Cornell undergraduate students.

He questioned them about their political attitudes, including how they felt
about a same-sex marriage ban and their support for President Bush's handling of
the Iraq War.

\"I created composites from subjects' answers to these and other questions,\" he
said. \"I also gave subjects a car-buying vignette, presented as part of a study
of purchasing a new car.\"

Masculinity-threatened participants also showed more interest in buying an SUV.
\"There were no increases for other types of cars,\" Willer said.

The study produced \"the predicted results,\" he said. \"The intention of the study
was to explore whether masculine overcompensation exists and where. But the
point isn't to suggest these are the only factors that can explain these
behaviors. Likewise, there may be a wide variety of other behaviors that could
increase when men are concerned about their levels of masculinity.\"

Willer said he and a colleague are planning additional research on subjects'
attitudes regarding violence toward women, using the same method for
manipulating masculine insecurity.

\"I'm planning another follow-up to the study that involves taking testosterone
samples from participants\" to see if testosterone levels are a factor in this
process, he added.

http://www.world-science.net/othernews/050806_mascfrm.htm

Biologists have been making considerable progress in identifying members of a special class of genes - those that shape an animal's behavior toward others of its species. These social behavior genes promise to yield deep insights into how brains are constructed for certain complex tasks.

Some 30 such genes have come to light so far, mostly in laboratory animals like roundworms, flies, mice and voles. Researchers often expect results from these creatures to apply fairly directly to people when the genes cause diseases like cancer. They are much more hesitant to extrapolate in the case of behavioral genes. Still, understanding the genetic basis of social behavior in animals is expected to cast some light on human behavior.

Last month researchers reported on the role of such genes in the sexual behavior of both voles and fruit flies. One gene was long known to promote faithful pair bonding and good parental behavior in the male prairie vole. Researchers discovered how the gene is naturally modulated in a population of voles so as to produce a spectrum of behaviors from monogamy to polygamy, each of which may be advantageous in different ecological circumstances.

The second gene, much studied by fruit fly biologists, is known to be involved in the male's elaborate suite of courtship behaviors. New research has established that a special feature of the gene, one that works differently in males and females, is all that is needed to induce the male's complex behavior.

Social behavior genes present a particular puzzle since they involve neural circuits in the brain, often set off by some environmental cue to which the animal responds. Catherine Dulac of Harvard has found that the male mouse depends on pheromones, or air-borne hormones, to decide how to behave toward other mice. It detects the pheromones with the vomeronasal organ, an extra scent-detecting tissue in the nose.

The male mouse's rule for dealing with strangers is simple - if it's male, attack it; if female, mate with it. But male mice that are genetically engineered to block the scent-detecting vomeronasal cells try to mate rather than attack invading males.

The mice have other means - sound and sight - of recognizing male and female. But curiously, nature has placed the sex discrimination required for mating behavior under a separate neural circuit aroused through the vomeronasal organ.

\"It was very surprising for us,\" Dr. Dulac said.

The gene that was eliminated from the mice is a low-level member of a presumably complex network that governs the inputs and outputs necessary for mating behavior. The most striking behavioral gene discovered so far is a very high level gene in the Drosophila fruit fly.

The gene is called fruitless because when it is disrupted in males they lose interest in females and instead form mating chains with other males. The male's usual courtship behavior is pretty fancy for a little fly. He approaches the female, taps her with his forelegs, sings a song by vibrating his wing, licks her and curls his abdomen for mating. If she is impressed she slows down and accepts his proposal. If not, she buzzes her wings at him, a gesture that needs no translation.

All these behaviors, researchers discovered several years ago, are controlled by the fruitless gene - fru for short - which is switched on in a specific set of neurons in the fly's brain. The gene is arranged in a series of blocks. Different combinations of blocks are chosen to make different protein products. The selection of blocks is controlled by a promoter, a region of DNA that lies near but outside the fru gene itself.

So far four of these fru gene promoters have been found. Three work the same way in both male and female flies. But a fourth selects different blocks to be transcribed, making different proteins in males and in females. This difference, it seemed, was somehow the key to the whole suite of male courtship behaviors.

Last month Barry J. Dickson of the Austrian Academy of Sciences provided an elegant proof of this idea by genetically engineering male flies to make the female version of the fruitless protein, and female flies to generate the male version. The male flies barely courted at all. But the female flies with the male form of fruitless aggressively pursued other females, performing all steps of male courtship except the last.

How does the male form of the fruitless protein govern such a complex behavior? Dr. Dickson and his colleagues have found that the protein is produced in 21 clusters of neurons in the fly's brain. The neurons, probably connected in a circuit, presumably direct each step of courtship in a coordinated sequence.

Surprisingly, female flies possess the same neuronal circuit. The presence of the male form of fruitless somehow activates the circuit , in ways that are still unknown.

Fruitless serves as a master switch of behavior, just as other known genes serve as master switches for building an eye or other organs. Are behaviors and organs constructed in much the same way, each with a master switch gene that controls a network of lower level genes?

Dr. Dickson writes that other such behavior switch genes may well exist but could have evaded detection because disrupting them - the geneticist's usual way of making genes reveal themselves - is lethal for the fly. (Complete loss of the fruitless gene is also lethal, and the gene was discovered through a lucky chance.)

Though researchers like to focus on specific genes, they are learning that in behavior, an organism's genome is closely linked to its environment, and that there can be elaborate feedback between the two.

Honeybees spend their first two to three weeks of adult life as nurses and then switch to jobs outside the hive as foragers for the remaining three weeks. If all foragers are removed from a hive, the nurse bees will sense the foragers' absence through a pheromone and assume their own foraging roles earlier. As the colony ages however, there are too few nurses, so some bees stay as nurses far longer than usual.

Gene Robinson, a bee biologist at the University of Illinois, has found that a characteristic set of genes is switched on in the brains of nursing bees and another set in foraging bees. This is an effect of the bees' occupation, not of their age, since both the premature foragers and the elderly nurses have brain gene expression patterns matched to their jobs.

Evidently the division of labor among bees in a hive is socially regulated through mechanisms that somehow activate different sets of genes in the bees' brains.

A remarkable instance of genome-environment interaction has been discovered in the maternal behavior of rats. Pups that receive lots of licking and grooming from their mothers during the first week of life are less fearful in adulthood and more phlegmatic in response to stress than are pups that get less personal care.

Last year, Michael J. Meaney and colleagues at McGill University in Montreal reported that a gene in the brain of the well-groomed pups is chemically modified during the grooming period and remains so throughout life. The modification makes the gene produce more of a product that damps down the brain's stress response.

The system would allow the laid-back rats to transmit their behavior to their pups through the same good-grooming procedure, just as the stressed-out rat mothers transmit their fearfulness to their offspring.

\"Among mammals,\" Dr. Meaney and colleagues wrote in a report of their findings last year, \"natural selection may have shaped offspring to respond to subtle variations in parental behavior as a forecast of the environmental conditions they will ultimately face once they become independent of the parent.\"

A full understanding of these behavior genes would include being able to trace every cellular change, whether in a hormone or pheromone or signaling molecule, that led to activation of the gene and then all the effects that followed. Dr. Robinson has proposed the name \"sociogenomics\" for the idea of understanding social life in terms of the genes and signaling molecules that mediate them.

The genes discovered so far mostly seem to act in different ways and it is hard to state any general rules about how behavior is governed.

\"It's early days and we don't have enough information to develop theories,\" Dr. Robinson said.

A question of some interest is how far the genetic shaping of behavior exists in people. Larry J. Young of Emory University, who studies the social behavior of voles, said that, in people, activities like the suckling of babies, maternal behavior and sexual drives are likely to be shaped by genes, but that sexual drives are also modulated by experience.

\"The genes provide us the background of our general drives, and variations in these genes may explain various personality traits in humans, but ultimately our behavior is very much influenced by environmental factors,\" he said.

Researchers can rigorously explore how behavioral genes operate in lower animals by performing tests that are impossible or unethical in people. \"The problem with humans is that it is extremely difficult to prove anything,\" Dr. Dulac said. \"Humans are just not a very good experimental system.\"

By JOHNNY HOOKS
Jun. 24, 2005

WHO DOESN’T LIKE PENGUINS? The dapper flightless birds are revered by young and old. Flipping on Entertainment Tonight recently, you may have caught an entire segment on the Warner Independent documentary called “March of the Penguins,” complete with waddling Emperor Penguins walking the red carpet.

Wide-eyed children proclaim to the camera lenses “We love them, everybody does right?” and “I just love their suits!” and “I wanna be a penguin!”

The scene changes to an average day on AM radio in Houston. Up and down the dial commentators proclaim the truth as they see it. Gays and lesbians are often vilified, attacked and eventually taunted with the question “If homosexuality is so normal, why don’t we see it in the animal kingdom?”

The simple answer is we do. Look at Roy and Silo, two real penguins who live in the Central Park Zoo. The story of Roy and Silo is now available in a charming book called “And Tango makes Three.”

Illustrated by Henry Cole, and written by Justin Richardson and Peter Parnell, the tale of Roy and Silo should bring a tear to the most jaded eye..

Their story became public when The New York Times outed the penguin pair in a February 2004 article called, “Love That Dare Not Squawk Its Name.”

In the article, Dinitia Smith recounted how for more than six years, Roy and Silo have exhibited what in penguin parlance is called “ecstatic behavior.” They entwine their necks, they vocalize to each other, they have sex.

WHEN OFFERED FEMALE companionship, both adamantly refused. And female penguins showed little interest in them as well. They are “to anthropomorphize a bit” gay penguins.

Roy and Silo were so committed to each other that they attempted to incubate egg shaped rocks on several occasions in their flawless nest.

Central park Zoo’s Rob Gramzay took note of their attempts and in 2000 finally gave the pair a fertilized egg from a female “donor.”

That egg was cared for and eventually produced the baby, Tango, who was raised like any other penguin.

Following along with Roy and Silo, readers can’t help but cheer the two on.

On a recent jaunt to the Aquarium of the America’s in New Orleans, this reviewer brought along a copy of the book, “And Tango Makes Three.”

After the zoologists had finished feeding the in-house penguins, he was asked about the tale of Roy and Silo. While he had no direct knowledge of the duo, he said “Well, there have been over 450 different documented examples of same-sex coupling in the wild.

Have you heard about those lesbian seagulls? Talk about commitment! Most people would be surprised to find committed same-sex animal couples.”

The open discussion of homosexual behavior in animals is relatively new. Frans de Waal, whose 1997 book, “Bonobo: The Forgotten Ape” saw an onslaught of differing opinions on animal sexuality. Bonobos apes closely related to humans, are wildly energetic sexually. Nearly all are bisexual and nearly half engage in same-sex activity.

However Paul L. Vasey, a professor of psychology and neuroscience at University of Lethbridge in Canada, warns about drawing such conclusions. “For some people, what animals do is a yardstick of what is and isn’t natural. They make a leap from saying if it’s natural, it’s morally and ethically desirable.”

According to the authors note at the end, “If you go to the Central Park Zoo, you can see Tango and her parents splashing about in the penguin house along with their friends…There are forty-two chinstrap penguins in the Central Park Zoo, and over ten million chinstraps in the world. But there is only one Tango.”

Maurice Sendak of “Where the Wild Things Are” said this of “Tango”: “A touching and delightful variation on a major theme.” Harvey Fierstein said, “This wonderful story of devotion is heartwarming proof that Mother Nature knows best!”

Odour and mating preferences
WHAT'S a girl to do when faced with the choice between a powerful action man who has great DNA but is likely to love her and leave her, and a carpet-and-slippers kind of bloke who will hang around and bring up the kids but may not be Mr Right in the genes department? Well, ideally, she should fool the latter into bringing up the former's children. And a piece of evidence that this is exactly what happens emerged this week from a research group led by Jan Havlicek of Charles University, in Prague.

Dr Havlicek and his colleagues were interested in discovering whether women are attracted by the smell of dominant men. A preference for the scent of dominants has been found in the females of other species, and scent is known to be important in attraction between the human sexes in other contexts, such as avoiding inbreeding. The attractiveness of body odour is also correlated with the attractiveness of the body it came from, even when presented separately from that body. But whether the odour of power—or, at least, of powerfulness—is attractive to women had not been established.

Deciding who is and is not a dominant male is the first question, of course. To do this, the researchers turned to one of the world's most widely used experimental animals, the hard-up male student. Their subjects were asked to rate such things as their tendency to correct others, to want to control conversations, and to surpass others' accomplishments, in a questionnaire designed to assess their dominance. In their paper in Biology Letters the researchers laconically observe that dominance in this questionnaire “corresponds to the scale ‘Narcissism’ in the widely used California psychological inventory”.

After baring their all in this manner, the volunteers had to wear cotton pads under their armpits for 24 hours to collect the sweat therefrom, and also had to lay off curries, beer, cigarettes and similar delights of student life that might affect the smell of their sweat. Surprisingly, given these constraints, the researchers managed to persuade 48 men to volunteer.

Compared with this, the female volunteers had it easy. They had to smell the pads and rate them for “intensity”, “sexiness” and “masculinity”. Okay, perhaps not that easy. They also had to vouchsafe whether they were single or in an on-going relationship with a man, and to submit to a saliva test that would show the phase of their menstrual cycle.

The upshot of the trial was that women did, indeed, find the odour of dominants sexier than that of wimps—but only in special circumstances. These circumstances were first that the woman was already in a relationship and second that she was in the most fertile phase of her cycle. In other words, dominant males' scent was only more attractive at the point where a woman could both conceive and cuckold her mate. Which, given previous studies that show dominant men are indeed more likely than others to leave a woman holding the baby, makes perfect sense.

This philosopher of science rejects claims of a universal human nature

By JR Minkel

Philosopher of science David Buller has a bone to pick with evolutionary psychology, the idea that some important human behaviors are best explained as evolutionary adaptations to the struggles we faced tens to hundreds of thousands of years ago as hunter-gatherers. In his new book, Adapting Minds, the Northern Illinois University professor considers--and finds lacking--the evidence for some of the most publicized conclusions of evolutionary psychologists: Men innately prefer to mate with young, nubile women, while women have evolved to seek high status men; men are wired to have a strong jealous reaction to sexual infidelity, while women react to emotional infidelity; and parents are more likely to abuse stepchildren than their genetically related children.

Buller doesn't reject evolutionary studies of the mind per se. Rather, he contends that \"Evolutionary Psychology,\" a set of assumptions about the nature and evolution of the human mind, has largely crowded out the possibility of a more pluralistic \"evolutionary psychology.\" Writer JR Minkel recently spoke to Buller to get a bead on his argument. An abridged and edited transcript of their conversation follows.

JR Minkel: What was your initial reaction to the conclusions of Evolutionary Psychology, and when did you first start having doubts about them?

David Buller: When I first started reading it, it just all seemed intuitively right to me. But as I followed the citation trail and actually started looking at the primary studies that were cited in support of those conclusions--and thinking seriously about the methods that had been employed in the studies, the presuppositions behind them, and whether there were alternative evolutionary hypotheses for the things studied that were not in fact being ruled out by the experiments--I began to find that it wasn't all that convincing.

JRM: Why did you feel the need to write a book, given the criticisms the field has already received?

DB: I didn't feel that there was a broader framework in which the whole paradigm was viewed as fundamentally problematic. I saw the writing of this book just as a desire to synthesize a variety of the problems I saw with the paradigm, some of which had been pointed out by other people already.

What I thought needed to be brought out for a more general readership were some of the methodological problems involved in these very highly publicized discoveries that evolutionary psychologists claim to have made; things that get covered in the New York Times on pretty much a weekly basis. I wanted to show people that there are grounds for skepticism.

JRM: Why do you say the evolutionary psychology paradigm is problematic?

DB: There are three foundational claims that it makes. One is that the nature of [evolutionary] adaptation is going to create massive modularity in the mind--separate mental organs functionally specialized for separate tasks. Second, that those modules continue to be adapted to a hunter-gatherer way of life. And third, that these modules are universal and define a universal human nature. I think that all three of those claims are deeply problematic.

If anything the evidence indicates that the great cognitive achievement in human evolution was cortical plasticity, which allows for rapidly adaptive changes to the environment, both across evolutionary time and [across] individual lifetimes. Because of that, we're not quite the Pleistocene relics that Evolutionary Psychology claims. [Regarding universality,] all of the evidence indicates that [behavioral] polymorphisms are much more widespread in all sexually reproducing populations than the idea of a universal human nature would require. So I think the theoretical foundations from which a lot of predictions get made, about what our mate preferences are going to be, or what the psychology of parental care is, are problematic because the theoretical foundation is mistaken.

JRM:In the book you also point out the difficulty of reconstructing the ancient environment that evolutionary psychologists argue has shaped the human mind.

DB: Even by their own account, human psychology evolved for the most part to deal with human psychology, to put it crudely. You can't be specific about what the adaptive demands were on human psychology without knowing something about the way that humans minds were working then, and that's something we just don't know.

JRM: Which conclusion of Evolutionary Psychology do you think has most captivated the public?

DB: Probably the issue of mate preferences, this whole idea that males have this ineluctable preference to mate with nubile females, and that females have this ineluctable preference to mate with high status males. As soon as you see those claims you can immediately think of a number of confirming examples of it. The evolutionary psychologist David Buss is very fond of pointing to Hollywood stars and saying, \"See, these people illustrate the truth of our claims.\" But when you look at the broader range of evidence that's out there I think it doesn't really support these claims.

As I point out in one section about male preferences, there's a tendency to focus on older males who reenter the mating market after divorce, and evolutionary psychologists take this to be pretty firmly clinching evidence in favor of their hypothesis. But that neglects over half of older males who remain mated to older women. Look at Paul Newman--a very high status male, but [he] has remained monogamously married to a woman his own age. Those are choices that males make, and you can't just exclude one half of the population from the data against which you're going to test your hypothesis.

My hypothesis is that in most men, the adaptation is a preference for similarly-aged mates--adjusted for sex differences in the ages at which reproductive maturity are reached--rather than an adaptation to prefer nubility. This preference tends to contribute to the selection of a nubile mate because most marrying men are young. The difference between my hypothesis and Evolutionary Psychology's claim can't be seen when looking at the mate choices of young males. It's only when we look at older males that the two hypotheses differ in their predictions. As I argue at some length in chapter five, I think the evidence on the whole favors my hypothesis.

JRM: Do you see any value in Evolutionary Psychology? You mention in the book that it has led to evolutionary hypotheses about jealousy, for example.

DB: It has led to the asking of questions that needed to be asked, so in that regard I think it's been a very positive development. Evolutionary theory has not been applied to the study of humans to quite the extent that it should have been to date. I think looking at an emotion like jealousy from an adaptationist standpoint is very positive. It stimulates lines of research that would not have occurred otherwise. But immediately then the paradigm kicks in with its big theoretical apparatus and says, \"Oh, well ok, but if jealousy is an adaptation, then differences in the sexes require differences in modules in the sexes.\" So then you get the whole account of jealousy that's propounded in the paradigm--the idea that there's an evolved sex difference, where males are sexually jealous and females are emotionally jealous. So while I think the paradigm has been an extremely positive development on the whole, it has tended to prematurely narrow the kinds of hypotheses that are considered about human evolution.

I have not seen in the literature any alternative evolutionary accounts of jealousy. The literature that tends to be critical of that particular hypothesis refers to it as the evolutionary account of jealousy and, in rejecting the particular hypothesis of an evolved sex difference, goes on to reject an evolutionary account of jealousy. I think that's premature. I think jealousy can be an adaptation but it doesn't require that there is an evolved sex differences in the design features of the male and female minds.

I have a colleague in the psychology department, Brad Sagarin, and we have started gathering some data to explore other evolutionary hypotheses [for jealousy], like the one that I articulate in the book. [Editor's note: Called the relationship jeopardy hypothesis, it supposes that men and women have the same evolved capacity to learn to distinguish threats to the relationship from nonthreats.] We're still just gathering data. One thing that we're talking about in the research group is ways of creating jealousy in a laboratory setting. Coming up with a way of doing this that is ethical is not at all that easy. The easy way is to use the same sorts of questionnaire studies that have been used before, but to broaden the questions that you use them to address.

One piece of propaganda that people in the Evolutionary Psychology paradigm have used in support of their approach is [to assert] that throughout the history of psychology, evolutionary thinking has been almost entirely absent. They present themselves as having the courage to ask evolutionary questions about human psychology. Certainly we have evolved, like all other life on the planet, and we should be looking at human psychology from an evolutionary perspective. My disagreement with the Evolutionary Psychology paradigm is with respect to what follows from taking an evolutionary perspective on human behavior and psychology. The paradigm [supposes] that a lot of very specific doctrines immediately begin to follow once you take that perspective, and I don't think that's true. It's much more wide open.

JRM: What are other examples of proposed evolutionary explanations for human behavior that fall outside the paradigm?

DB: Some of the examples I discuss in the book are Barbara Smuts and David Gubernick's mating effort hypothesis concerning the evolution of marriage, and Kristen Hawkes's \"grandmother hypothesis\" for the evolution of menopause. In my opinion, these are terrific examples of work in evolutionary psychology, as opposed to Evolutionary Psychology. One significant difference between this work and the Evolutionary Psychology paradigm is that it isn't driven by an underlying \"Grand Unified Theory\" about the nature and evolution of the human mind. The good work to date, I think, has tended to be piecemeal, focused only on narrow aspects of human life history and decision-making.

The other major topic you address in the book is child abuse. You went so far as to collect data from the National Data Archive on Child Abuse and Neglect to examine patterns of abuse in the U.S. Why are you skeptical of the claim that parents are more likely to abuse stepchildren?

DB: It's a long and complicated argument. To oversimplify, I will say, first, we need to make sure that we're looking at the right sample. As I argued, to test evolutionary psychology's hypothesis, we need to look at physically abused children, not sexually abused children or children who were the victims of very broadly defined neglect. Second, in my study, the sample of physically abused children was 10 times the size of the sample in [a study by evolutionary psychologists Martin Daly and Margo Wilson]. Third, the differential I found in that larger U.S. study is readily accounted for by U.S. data regarding a diagnostic bias against those classified as stepparents. Fourth, I found clear evidence that much abuse in stepfamilies is at the hands of genetic parents. These things conspire to raise doubts about the \"received view\" of stepparental abuse.

JRM: Was your study peer-reviewed?

DB: A very brief version of it appears in an article of mine in the June issue of Trends in Cognitive Sciences. So some of it was published in a peer-reviewed journal a little after the release of my book. It wasn't rejected by peer-reviewed journals, either. I never submitted the research apart from my book.

JRM: Another recent book, The Case of the Female Orgasm, by biologist and philosopher of science Elisabeth Lloyd, examines the evidence for various adaptive explanations of female orgasms, and concludes that it has no evolutionary function. Do you think she's right?

DB: I haven't read the book yet. However, I've read her earlier work on female orgasm, I've seen her give a couple of talks on her research, and I've discussed her work with her briefly. I'm not completely convinced that Lloyd is right that female orgasm has no evolutionary function, although my mind could change once I read the whole book. She presupposes that male orgasm has a direct reproductive function--namely, to inseminate. But this conflates ejaculation and orgasm. Insemination is the function of ejaculation. Ejaculation and orgasm are actually distinct phenomena subserved by separate and dissociable physiological mechanisms. Ejaculation is all that's necessary for the function of insemination. So there's a problem about male orgasm: Why has it evolved? Clearly, the mechanisms subserving the sensation of orgasm are the evolutionary latecomers. So at some point in our evolutionary history, well before the emergence of Homo sapiens, there may have been non-orgasmic ejaculators and orgasmic ejaculators. Given where we've arrived, clearly the latter outreproduced the former. One possible reason is that orgasms drove the orgasmic ejaculators to have sex more often in order to induce the pleasurable sensation. The common early developmental pathway of males and females would have endowed females with the mechanisms for orgasm as well, as Lloyd herself shows, following [evolutionary psychologist] Donald Symons. Once so endowed, orgasm could have performed the same motivational role in women. In that case, in both sexes, orgasm would be an adaptation for a higher frequency of sex--hence, presumably, a higher rate of offspring production relative to our ancestors without the pleasurable sensation of orgasm. Of course, this is highly speculative, and--to repeat--I haven't made my way through all of Lloyd's arguments. But at first glance, I'm skeptical.

JRM: Do you think people tend to resist any evolutionary account of human behavior because it seems to reduce important aspects of our emotional lives--romantic and parental love, for example--to an impersonal desire for reproductive success?

DB: When we introspectively focus on the proximate cause of our behavior, we tend to think it's sufficient explanation of my getting married that I love this person, and that I have no desire to have children. So the idea that [reproduction] is a complete explanation sets up a resistance in a lot of people [to questions such as] why is it that these emotions have evolved, and what evolutionary function do they serve? That's actually a different kind of explanation. It's not an explanation of how proximate mechanisms function, but an explanation of why we have those kinds of proximate causes driving our behavior.

Even an evolutionary biologist like [the late Stephen Jay] Gould was prone to this slippage between proximate and ultimate explanations, and then to rejecting an ultimate explanation because of thinking a particular proximate explanation was sufficient. In Gould's critique of Evolutionary Psychology, he said, \"I don't think that males are willing to rear babies only because clever females beguile us. A man may feel love for a baby because the infant looks so darling and adorable.\" Gould was slipping there between the proximate and ultimate explanations. The ultimate explanation is female sexual selection for care-giving males. The proximate explanation has to do with what causes males to respond that way to children, and that can be entirely because they look so adorable. That's not incompatible with an evolutionary account.

JRM: At the end of the book you spend a chapter arguing that there is no universal human nature. Can you explain what you mean?

DB: I go by what others have used the term to mean. If by human nature all you mean is whatever humans do, then absolutely there's a human nature, and an evolutionary perspective on human beings will inform us about human nature. But traditionally the concept of human nature has [been] a much more theoretically loaded concept, which is that there are certain things that it's normal for humans to be, and that constitute human nature. The concept of human nature [therefore] only refers to a partial subset of all of the manifest diversity that we view among human beings. And I think that notion has no foundation in evolutionary theory. That notion is in fact a vestige of 19th-century natural theology.

A truly evolutionary view of our species recognizes that variation is not some noise in the system, but is the system itself. And so in an important sense there's no such thing as the human mind, which an evolutionary perspective on will illuminate us about, but rather there are a variety of different kinds of minds out there, all of which have evolved, and in many cases the variety of kinds of minds are maintained by frequency dependent selection. In the nontrivial sense, there's simply no such thing as human nature if you take evolutionary theory seriously. What's common at one particular time in the [evolutionary] process won't necessarily be common at a different time in the process within the same species.

JRM: Does the idea of evolved differences between the sexes stand or fall with the Evolutionary Psychology paradigm?

DB: These are tentative answers. I don't think that it does stand or fall with Evolutionary Psychology, even though they have been the principal purveyors of the idea of evolved sex differences. I don't think there's good evidence for the sex differences that I examine most in the book, namely in the design features of the mind underlying jealousy and mate preference. The extent to which there's good evidence of evolved sex differences is actually my next book project.

JRM: What hope do we have of understanding how evolution shaped our minds?

DB: One approach is to work from the past forward, which is the approach taken by the Evolutionary Psychology paradigm; to try to think about the adaptive problems that drove human psychological evolution, and how ancient problems are reflected in the current design of the mind. But another approach is to work from the present backwards; to look at how humans make decisions regarding things like mating and parental care; to model, from an adaptive standpoint, the decision making that humans make in contemporary environments; and to try to get a fix on the nature of reasoning involved. If you can identify ways in which people are behaving in a highly adaptive manner, that can perhaps--perhaps--inform you about some of the evolutionary pressures that gave rise to it. But that's still always going to be a rather highly speculative step of the process.

Only when the community of researchers who are applying evolutionary theory to human psychology begin to broaden the ways in which they do that will good answers begin to emerge. And if my book can have any positive effect I would hope it would be to prompt people to think about alternative hypotheses and different ways in which evolutionary theory might inform psychology.

JRM: What value can philosophers add to science?

DB: I have no doubt that some readers are going to say that I've brought nothing to these issues, because philosophers should stick to what they know--namely, nothing. And there's an extent to which I agree with them. Philosophy as a field is not a body of knowledge to be known. What we philosophers do get trained for is analysis of reasoning. I think philosophers can contribute quite a bit to ongoing scientific research in this respect, becausc theory and evidence aren't tightly and obviously connected to one another. Evidence usually only speaks to theory after some tortured chain of reasoning to connect the two. And it's that tortured chain of reasoning [that] philosophers are trained to look at with a critical eye.

I'm not telling the world that everything in my book is right, so everyone should stop listening to evolutionary psychologists. I propose something different: Inform yourselves. Please. Go out and read the stuff by evolutionary psychologists and read my book, then make up your own minds about what you think is right and wrong. I think people should look at both sides before deciding.

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In Miranda July's shrewdly observed \"Me and You and Everyone We Know,\" a 14-year-old boy and his 7-year-old brother sit in front of a computer screen engaging in an increasingly common form of sex education: an online chat with an anonymous woman. Although the 14-year-old is savvy enough to guess that they could be talking, say, to a grossly overweight man instead of some hot babe, his little brother suggests, \"Ask if she likes baloney,\" then innocently offers a nonsensical, physically impossible act that reminds us he is not so far from his potty training days. The online response is, \"You are crazy, and you are making me very hot.\"

Precocious sexual knowledge - far beyond what children and teenage characters can absorb, and often with devastating consequences - has become a staple of current independent films. In the French film \"Lila Says,\" the title character is a 16-year-old whose wealth of sexual knowledge and free-wheeling behavior leads the town to think she may actually be a whore. In Gregg Araki's unexpectedly eloquent \"Mysterious Skin,\" two boys who are molested by their Little League coach grow up to be a teenage hustler and a guy who believes he was abducted by aliens. (All three films are playing in New York and a handful of other cities, and will expand to more cities through the next month or so.) And movies with similar themes will arrive in the next month, including Don Roos's comic romance \"Happy Endings\" and the satiric \"Pretty Persuasion.\"

But while these filmmakers are highly aware of the dangers such early knowledge can pose - from Internet predators to unwanted pregnancy - their films do not display the knee-jerk judgments you might expect, and that shaped the 2003 film \"Thirteen.\" Where \"Thirteen\" was praised for its audacity in depicting 13-year-olds having sex and doing drugs, it was really a traditional cautionary tale. The current films are more complex. They often blame the big, wide media world and other social influences that cause children to grow up too fast. But they also accept this early loss of innocence as the new way of the world and move on from there. In their bewildered acceptance of this new reality, the films reflect the current social moment, in all its fraught confusion, more astutely than any alarmist work could.

It's not surprising that all these films are smaller, independent works; they can afford to address the riskier themes that big-budget movies avoid. The current films also share sophisticated narratives and graceful styles that make their unsettling themes palatable. \"Me and You\" is directly about the romance of a lonely artist (played by Ms. July) and a recently separated shoe salesman (John Hawkes) whom she willy-nilly decides is her soul mate. But the difficulty of forging a connection is reflected in the next generation - the young brothers are the salesman's sons - in which children and teenagers confront a disorienting sexual world.

The family's neighbors include two slightly older teenage girls who use the 14-year-old brother as a practice object for oral sex, asking him to judge which of them does it better. When the father's seemingly respectable co-worker makes lewd suggestions to the girls, they teasingly kiss in front of him. But when they finally dare to ring his doorbell, he cowers and hides.

Ms. July's sense of a dangerous world encroaching is deflected by such last-minute twists. Yet it is still chilling when the 7-year-old arranges a real-life date with the mysterious online lover. And it may be even more chilling that the father is not callous or neglectful, just hapless and not very smart, an ordinary guy. Ms. July acknowledges the risks of precocious, half-baked sexual knowledge, but in keeping with the endearing tone of her film, willfully evades those dangers.

There is no such evasion in \"Lila Says.\" Set in a poor Marseille neighborhood, Ziad Doueiri's gripping film seems headed for tragedy from the start. The beautiful blond Lila is not just another sexually active 16-year-old, no longer a rarity. She is so bluntly, openly sexual that she enters the film by offering to expose herself to a stranger, Chimo, the 19-year-old who falls in love with her yet is intimidated by her experience. Chimo's friends regard Lila as a slut; yet if the brutal finale they set in motion is all too predictable, one crucial element is not. Chimo discovers Lila's scrapbook, in which she has pasted magazine articles about subjects like amateur porn on the Internet, clippings that suggest how much of her sexual knowledge was shaped by a world she was not ready to understand.

\"Lila Says\" is so delicately balanced that it manages to have things both ways. It is erotic, notably in a sexual encounter between Lila and Chimo on a motorbike, yet also conveys a sad sense of lost innocence. Despite the film's melodrama, that balance creates a hauntingly realistic aura.

Its least convincing element comes when Lila's aunt and guardian makes a pleading sexual advance toward her. The theme is never picked up again, so the abuse seems like a forced, convenient explanation for Lila's behavior.

The idea of childhood abuse is used more intelligently in \"Mysterious Skin.\" The molestation scenes are not graphic, but they are so clear and depicted with such immediacy that at first it seems the film has crossed a line into a completely nonjudgmental realm. But \"Mysterious Skin\" adheres to the boys' points of view so rigorously that the abuse reflects their own confusion, just as the film's lyricism suggests their emotional escape strategies. By the end, when the anguish inflicted on the boys becomes apparent, we see that the film realizes the abuse was monstrous. Mr. Araki has always been a provocative filmmaker, not an ingratiating one, and while \"Mysterious Skin\" is lucid about the horrible violation of the boys, it refuses to preach at us, and much of its power comes from that unflinching approach.

While all these films matter-of-factly assume that sexual knowledge arrives earlier and earlier, \"Happy Endings\" is essentially a cheerful movie, even though its plot is set off when a teenage stepbrother and stepsister have sex that results in a pregnancy. \"Pretty Persuasion\" is caustic, as several 15-year-old girls maliciously and falsely accuse a teacher of abuse, setting off a media circus. That such varied tones can be spun from a common idea says that precocious sexuality is considered a pervasive part of our world, even if the filmmakers have no better idea of what to do with that knowledge than the 7-year-old knows what to do on his date.

Some people are attracted to women; some are attracted to men. And some, if Sigmund Freud, Dr. Alfred Kinsey and millions of self-described bisexuals are to be believed, are drawn to both sexes.

But a new study casts doubt on whether true bisexuality exists, at least in men.

The study, by a team of psychologists in Chicago and Toronto, lends support to those who have long been skeptical that bisexuality is a distinct and stable sexual orientation.

People who claim bisexuality, according to these critics, are usually homosexual, but are ambivalent about their homosexuality or simply closeted. \"You're either gay, straight or lying,\" as some gay men have put it.

In the new study, a team of psychologists directly measured genital arousal patterns in response to images of men and women. The psychologists found that men who identified themselves as bisexual were in fact exclusively aroused by either one sex or the other, usually by other men.

The study is the largest of several small reports suggesting that the estimated 1.7 percent of men who identify themselves as bisexual show physical attraction patterns that differ substantially from their professed desires.

\"Research on sexual orientation has been based almost entirely on self-reports, and this is one of the few good studies using physiological measures,\" said Dr. Lisa Diamond, an associate professor of psychology and gender identity at the University of Utah, who was not involved in the study.

The discrepancy between what is happening in people's minds and what is going on in their bodies, she said, presents a puzzle \"that the field now has to crack, and it raises this question about what we mean when we talk about desire.\"

\"We have assumed that everyone means the same thing,\" she added, \"but here we have evidence that that is not the case.\"

Several other researchers who have seen the study, scheduled to be published in the journal Psychological Science, said it would need to be repeated with larger numbers of bisexual men before clear conclusions could be drawn.

Bisexual desires are sometimes transient and they are still poorly understood. Men and women also appear to differ in the frequency of bisexual attractions. \"The last thing you want,\" said Dr. Randall Sell, an assistant professor of clinical socio-medical sciences at Columbia University, \"is for some therapists to see this study and start telling bisexual people that they're wrong, that they're really on their way to homosexuality.\"

He added, \"We don't know nearly enough about sexual orientation and identity\" to jump to these conclusions.

In the experiment, psychologists at Northwestern University and the Center for Addiction and Mental Health in Toronto used advertisements in gay and alternative newspapers to recruit 101 young adult men. Thirty-three of the men identified themselves as bisexual, 30 as straight and 38 as homosexual.

The researchers asked the men about their sexual desires and rated them on a scale from 0 to 6 on sexual orientation, with 0 to 1 indicating heterosexuality, and 5 to 6 indicating homosexuality. Bisexuality was measured by scores in the middle range.

Seated alone in a laboratory room, the men then watched a series of erotic movies, some involving only women, others involving only men.

Using a sensor to monitor sexual arousal, the researchers found what they expected: gay men showed arousal to images of men and little arousal to images of women, and heterosexual men showed arousal to women but not to men.

But the men in the study who described themselves as bisexual did not have patterns of arousal that were consistent with their stated attraction to men and to women. Instead, about three-quarters of the group had arousal patterns identical to those of gay men; the rest were indistinguishable from heterosexuals.

\"Regardless of whether the men were gay, straight or bisexual, they showed about four times more arousal\" to one sex or the other, said Gerulf Rieger, a graduate psychology student at Northwestern and the study's lead author.

Although about a third of the men in each group showed no significant arousal watching the movies, their lack of response did not change the overall findings, Mr. Rieger said.

Since at least the middle of the 19th century, behavioral scientists have noted bisexual attraction in men and women and debated its place in the development of sexual identity. Some experts, like Freud, concluded that humans are naturally bisexual. In his landmark sex surveys of the 1940's, Dr. Alfred Kinsey found many married, publicly heterosexual men who reported having had sex with other men.

\"Males do not represent two discrete populations, heterosexual and homosexual,\" Dr. Kinsey wrote. \"The world is not to be divided into sheep and goats.\"

By the 1990's, Newsweek had featured bisexuality on its cover, bisexuals had formed advocacy groups and television series like \"Sex and the City\" had begun exploring bisexual themes.

Yet researchers were unable to produce direct evidence of bisexual arousal patterns in men, said Dr. J. Michael Bailey, a professor of psychology at Northwestern and the new study's senior author.

A 1979 study of 30 men found that those who identified themselves as bisexuals were indistinguishable from homosexuals on measures of arousal. Studies of gay and bisexual men in the 1990's showed that the two groups reported similar numbers of male sexual partners and risky sexual encounters. And a 1994 survey by The Advocate, the gay-oriented newsmagazine, found that, before identifying themselves as gay, 40 percent of gay men had described themselves as bisexual.

\"I'm not denying that bisexual behavior exists,\" said Dr. Bailey, \"but I am saying that in men there's no hint that true bisexual arousal exists, and that for men arousal is orientation.\"

But other researchers - and some self-identified bisexuals - say that the technique used in the study to measure genital arousal is too crude to capture the richness - erotic sensations, affection, admiration - that constitutes sexual attraction.

Social and emotional attraction are very important elements in bisexual attraction, said Dr. Fritz Klein, a sex researcher and the author of \"The Bisexual Option.\"

\"To claim on the basis of this study that there's no such thing as male bisexuality is overstepping, it seems to me,\" said Dr. Gilbert Herdt, director of the National Sexuality Resource Center in San Francisco. \"It may be that there is a lot less true male bisexuality than we think, but if that's true then why in the world are there so many movies, novels and TV shows that have this as a theme - is it collective fantasy, merely a projection? I don't think so.\"

John Campbell, 36, a Web designer in Orange County, Calif., who describes himself as bisexual, also said he was skeptical of the findings.

Mr. Campbell said he had been strongly attracted to both sexes since he was sexually aware, although all his long-term relationships had been with women. \"In my case I have been accused of being heterosexual, but I also feel a need for sex with men,\" he said.

Mr. Campbell rated his erotic attraction to men and women as about 50-50, but his emotional attraction, he said, was 90 to 10 in favor of women. \"With men I can get aroused, I just don't feel the fireworks like I do with women,\" he said.

About 1.5 percent of American women identify themselves bisexual. And bisexuality appears easier to demonstrate in the female sex. A study published last November by the same team of Canadian and American researchers, for example, found that most women who said they were bisexual showed arousal to men and to women.

Although only a small number of women identify themselves as bisexual, Dr. Bailey said, bisexual arousal may for them in fact be the norm.

Researchers have little sense yet of how these differences may affect behavior, or sexual identity. In the mid-1990's, Dr. Diamond recruited a group of 90 women at gay pride parades, academic conferences on gender issues and other venues. About half of the women called themselves lesbians, a third identified as bisexual and the rest claimed no sexual orientation. In follow-up interviews over the last 10 years, Dr. Diamond has found that most of these women have had relationships both with men and women.

\"Most of them seem to lean one way or the other, but that doesn't preclude them from having a relationship with the nonpreferred sex,\" she said. \"You may be mostly interested in women but, hey, the guy who delivers the pizza is really hot, and what are you going to do?\"

\"There's a whole lot of movement and flexibility,\" Dr. Diamond added. \"The fact is, we have very little research in this area, and a lot to learn.\"