Lay down your sat-navs, the journey is over: the destination a mirage. Or is it? According to new research carried out by scientists at King's College, London, the mysterious G-spot, the sexual pleasure zone said to be possessed by some women but denied to others, like Atlantis, is a myth. It doesn't exist.

Or does it? Tim Spector, professor of genetic epidemiology, who co-authored the research, is quoted in the Sunday Times as saying, "Women may argue that having a G-spot is due to diet or exercise but in fact it is virtually impossible to find real traits. This is by far the biggest study ever carried out and it shows fairly conclusively that the idea of the G-spot is subjective."

"Fact", you say, Professor Spector? Whether or not the G-spot exists – an issue that's been controversial for decades (it might or might not mirror the prostate gland) – a debate will be triggered next week when the study is published in the Journal of Sexual Medicine. What constitutes a "fact" in the scientific analysis of female sexual arousal is far from clear. But that hasn't stopped a steady stream of male "specialists" from asserting unequivocally that when it comes to female plumbing, and the best ways of tapping it to activate desire, they really know what they're talking about. And I don't just mean Freud.

For instance, Dr William Acton, a gynaecologist writing in the 1850s, asserted on the basis of his intimate knowledge of his female patients, "The majority of women (happily for them) are not very much troubled with sexual feelings of any kind."

And here is the nub of why research largely based on what women say about their sexual lives is so highly subjective that it's pretty doubtful it can be called science. It's conceivable, for example, that in Acton's time sex did leave many women cold. However, this might have been for a whole range of reasons that were not so much biological as social. Indifference – or tolerance for the sake of her man – was deemed the best position for a nicely brought up young lady. It's also conceivable that some women did linger long and pleasurably on the lust frontier but they were unlikely to disclose this to the good doctor for fear of being considered a slut, a nymphomaniac, unhinged or all three. "Science" has a long history of discovering only part of the female story.

This latest research is part of a 15-year study of twins, headed by Spector, to examine a range of issues including arthritis, the process of ageing and personality traits. In the G-spot research, 1,804 British women aged 23-83 answered questionnaires. All were pairs of identical or non-identical twins. Identical twins share genes, while non-identical pairs share 50% of theirs. According to the scientists, if one identical twin reported having a G-spot it was more likely that the other would too – but this pattern did not emerge.

The 56% of women overall who claimed to have a G-spot tended to be younger and more sexually active. Now, just as the women in Dr Acton's era, some of those in the cohorts of identical twins apparently without a G-spot, could have a range of reasons for asserting this view (including that the G-spot is still undiscovered) – none of them scientific. It's also pertinent to ask why the 56% who believe they do have a G-spot are apparently considered to be fantasising.

In the beginning, it was anatomical evidence that first flagged up the female pleasure zone rather than question and answer sessions. Regnier de Graaf identified female ejaculation in the 17th century, as well as an erotic area running the length of the urethra – the de-G spot? This was rediscovered in the 1950s by Ernst Grafenberg (who gave us the G in G-spot) and more recently Beverly Whipple has published a number of studies allegedly proving that the G-spot does exist. "The biggest problem with their findings is that twins don't generally have the same sexual partner," Whipple says of the King's College research.

I haven't a clue whether the G-spot exists, nor do I much care. But what does matter is the importance of not removing the specific context of a woman (or a man's) life when conducting these kinds of studies: we are obviously more than the answers we give. Partners; age; poverty; upbringing; disposition; inhibition; anxiety about others might think and a whole lot more all play a part in what we say, or don't say, about the routes to sexual satisfaction and our personal geography of arousal.

Andrea Burri, who also led the research, says that she is anxious to remove feelings of "inadequacy or underachievement" that might affect women who fear they lacked a G-spot. Ironically, it's precisely this mechanistic view of sex that probably adds to anxiety. Apart from the "discovery" of the clitoris, the only part of the male or female anatomy dedicated purely to pleasure, does it really matter which bits do what? And when the focus is entirely on the anatomical, what is sometimes pushed to one side is the impact of the still powerful cocktail of conditioning, expectations and plain old-fashioned exhaustion.