We owe a lot to the sex lives of Greeks. Ancient Greece gave us the origins of the names and concepts for homosexuality, homophobia and nymphomania, as well as narcissism and pederasty. The Romans talked freely to each other in toilets and were equally community-minded when it came to sex, with a reputation for lasciviousness and orgies. Georgians, we believe, were smutty, and Victorians were prudes and hypocrites. (All of these are partial truths.) We like to use sex as a mirror of an era, and to make judgments accordingly. What then, are we to make of us right now?

This is the most sex-positive age ever, right? We are liberal and comfortable with sex like no other people have ever been. Our magazines publish articles on how to get on better with your clitoris. Porn is freely available (and accessed by teenagers). Erotic books are bestsellers, however badly written. TV broadcasts shows in which the contestants are naked, or have sex in a box, or make a sex tape on camera. If sexual choice were a shop, it would be a hypermarket, with dizzyingly long aisles of every possibility: straight, gay, bi, trans, poly, fluid, each with its own culture and each widely accepted.

In this sex-positive version of reality, we have been unleashed from the bonds of church and religion, and suffocating family expectation; we are free, and we’re enjoying being easy. And society’s greater liberalism is matched by better scientific understanding of sex and the body parts that we use for it. This has been helped by the scientific gaze finally turning to the 51% of the population that it had mostly ignored, so that we know now that the clitoris, though smaller than the penis, has way more nerve endings. Despite what every Hollywood and TV scriptwriter believes, we may finally be accepting that more than 30% of women will not orgasm with penetration alone.

Millennials are having less sex than their parents; young people, we are told, are in a 'sex drought'

Sex and power have come together to positive effect elsewhere, with the last couple of years of the #MeToo movement. The use of power by men to get sex is as old as the Roman hills, and it is still endemic – along with appallingly low prosecution rates for rape – but something in that balance of power may have shifted, and for the good.

How comforting this sex-positive vision is. How sophisticated and liberal we are.

Except. A paper in a recent issue of the British Medical Journal summed up the findings of three huge national surveys into sexual attitudes, called Natsal, the latest of which was in 2012. Natsal is British in focus, but some of its findings are reflected globally: worldwide, we are having less sex less frequently and are more upset about it. In Britain, most of the decline in sexual frequency is in people aged over 25 and in long-term relationships. In the US, the over-50s reported the largest decline in how often they had sex, though Finnish middle-aged men reported they were getting sex more frequently. In Japan, the most sexual inactivity was in young single people. Millennials are having less sex than their parents; young people, we are told, are in a “sex drought”.

Some other disquieting facts: girls as young as nine are now having surgery to modify their vulvas, and rates of labiaplasty are increasing 45% year-on-year. There is now a labiaplasty known as the “Barbie”, which does what it says and reduces female genitalia to doll-like smooth uniformity. That must be because alongside all the sex positivity is another message: you are inadequate and wrong. Hairless, labia-free female bodies; porn-hard erections; dizzying sexual possibility. If you don’t want to eat guacamole off your bisexual lover while multiple-orgasming in at least three different positions, but only on a Thursday, what’s wrong with you?

Meanwhile, when the couples therapist Esther Perel did a Ted talk in 2013 on “the secret to desire in a long-term relationship”, it was watched 17m times on Ted and YouTube. All these numbers and facts point to a gap between the public, digital version of sex and the reality: that we are not getting enough of it and that when we do get it, it’s not satisfying.

Our sexual landscape may look like the promised land, but not everyone wants to travel there. This may be down to the way our relationships have changed. Marriage used to be more straightforward: an economic arrangement with clear, though not fair, expectations. For women, security, a home and children and the right not to be raped by the nearest powerful man, or at least a lesser probability of that happening. For men, succession. Now, Perel says: “We want our partner to still give us all these things, but in addition I want you to be my best friend and my trusted confidant and my passionate lover to boot, and we live twice as long.”

Esther Perel’s Ted talk on the secret to desire in a long-term relationship

In their paper, the BMJ authors were careful to skewer expected conclusions. Pornography was too easy to blame, and in fact a US study showed that declines in sexual frequency were greatest among those who didn’t watch it. If we are in a state of anxious disconnect between public sex and our private activities, then it is to be expected: we’re knackered. Middle-aged women reported exhaustion as one of the main reasons they were having less sex. Having children later in life, as we now tend to do, leaves those in middle life with small children and ageing parents and full-time jobs, all at once. No wonder they see a bed and want only to sleep in it.

Some of these figures could be because now that sex is primetime and ubiquitous, we feel more able to be honest about how much – or how little – we’re actually getting. But the researchers also noted that rates began to drop in 2007 and 2008. In 2007, the iPhone was launched, and in 2008, the world collapsed into recession. Anxiety, stress and exhaustion have led millions of people to be prescribed antidepressants (one in six Britons in 2017) – which are designed to combat those things but also dull libido. It is a heady package. “Should frequency of sexual contact serve as a barometer for more general human connectedness,” wrote the BMJ authors, “then the decline might be signalling a disquieting trend.”

Many species appear to have purely reproductive sex. That we don’t, that we have an erotic life too, is a bonus and a blessing. But it is also the source of dismay, dissatisfaction, puzzlement, frustration, mystery, worry, delight and obsession.

There may be a clearer lens being pointed at our sexual workings and wants, but our worries, fears and wonder about sex will outlive us all.