Born this way? Belle de Jour believes we're all bisexual

How do you define sexual orientation: on a scale or in a box? Set at birth, or a social construct? Questions such as these have vexed scientists and sociologists for centuries.

“I assume everyone is [bisexual] as a kind of baseline," Dr Brooke Magnanti (the forensic scientist and former call girl also known as Belle de Jour) said this week, setting out her stall in an interview with the Evening Standard. 

"I think I’m on the record as being bisexual but hetero-romantic. I’ll have sex with anyone but I like relationships with men."

Her beliefs tally with half of British 18-24-year-olds, who confidently say they are neither straight nor gay, but somewhere in between. 

The 2015 research, by YouGov, asked respondents to place themselves on the Kinsey Scale, developed by the US biologist Alfred Kinsey in the 1940s.

On his model, level zero is 'exclusively heterosexual’ and level six 'exclusively homosexual’. Under-24s were more than six times more likely than the oldest group to identify themselves as bisexual, to some degree.

Are we all born bisexual?

It was Sigmund Freud who first theorised  that all human beings are born 'innately' bisexual - based on the knowledge that in the womb, human babies are hemaphroditic - but that most become monosexual over the course of development.

But the concept goes back much further than that: a defined straight/gay/bi divide doesn't seem to have existed in Ancient Greek or Japanese society. In Homer's Iliad, it's essentially implied that Achilles has relationships with women and his friend and sparring partner Patroclus, and this isn't depicted as particularly unusual.

In Japan, sexual relationships were allegedly common among the famous samurai, or warrior class, and were said to result in a lifelong friendship; though the sexual component was expected to end once the young man came of age and found a wife.

But The Bisexual Index, a UK bisexual activist group fighting biphobia, is clear: "The often quoted 'Everyone is bisexual really' is utter rubbish. When people say this they hardly ever include themselves for starters. It's a phrase people use to dismiss bisexuality - after all, if we were the majority we needn't kick up a fuss."

Why is bisexuality contentious?

If bisexuality is not a modern concept, it remains an ever-divisive one. Theoretically, we live in a society which allows people to fall in love or lust with whoever they wish, but no matter how many Angelina Jolies or Cara Delevignes identify as bisexual, some still dismiss it as youthful experimentation along the road to embracing one’s “real” sexual orientation.

A Pew Research Center survey suggested bisexuals are less likely than gay men or lesbians to have “come out” to the important people in their life, because they didn't want to deal with misconceptions that they were indecisive or incapable of monogamy — stereotypes that exist among straights, gays and lesbians alike.

Brad S. Kane, a board member of the American Institute of Bisexuality, told the New York Times: "Even within the gay community, I can’t tell you how many people have told me, ‘Oh, I wouldn’t date a bisexual.’ Or, ‘Bisexuals aren’t real.’ There’s this idea, especially among gay men, that guys who say they’re bisexual are lying, on their way to being gay, or just kind of unserious and unfocused.”

What does science say?

One study in 2015 suggested that most women are either bisexual or gay but "never straight". The University of Essex research found that though lesbians are much more attracted to the female form, most women who say they are straight are in fact aroused by videos of both naked men and naked women.

The study involved 345 women whose responses to being shown videos of naked men and women were analysed. The results, which were based on elements such as whether their pupils dilated in response to sexual stimuli, showed that 82 per cent of the women tested were aroused by both sexes. Meanwhile of the women who identified as straight, 74 per cent were strongly sexually aroused by videos of both attractive men and attractive women.

What do the stats say?

The Office of National Statistics last year released data which showed the number of young people identifying as bisexual had risen by 45 per cent over the last three years. 

The stats showed that women are more likely to identity as bisexual (0.8 per cent) than lesbian (0.7 per cent), whereas men are more likely to report as gay (1.6 per cent) than bisexual (0.5 per cent).

If the figures seem small, writer Anna Hart, who fell in love with a girl before marrying her husband, believes their significance is huge: "what these latest statistics seem to be telling us is that that fewer young people feel that being outside the boundaries of traditional relationship conventions is 'inconceivable’.... liking both genders is simply not a big deal anymore."