Whether or not or how a woman achieves an orgasm was and continues to be a source of anxiety, misery and joy – as well as a matter of scientific scrutiny.

American Alfred Kinsey (1894–1956), a lepidopterist turned sex specialist, studied the sexual behaviors and beliefs of the American public in the manner of an entomologist, meticulously cataloging our quirky likes and dislikes in the manner of a butterfly collector archiving specimens. 'There's not much science here,' he is said to have remarked about the quality of mainstream medical beliefs concerning sex. He therefore sought to improve our understanding as any serious scientist would: by collecting data. Lots of it. In all, he and his team surveyed more than 18,000 Americans–but he had in fact hoped to interview more than 100,000 people.

One of Kinsey's most incendiary findings: documenting that the prevalence of homosexuality was far higher than most Americans at the time assumed. He estimated that 37 per cent of men had experienced a homosexual encounter and 10 per cent of men are 'exclusively' homosexual. Kinsey disliked the parsing of people into exclusively 'gay' or 'straight' categories and declared that sexual preferences lie on a spectrum. Humans are not born into binary boxes.

'The study of sex was really almost a hidden subject at the beginning of the twentieth century–when Kinsey published his findings so publicly, the world went ballistic,' says Dame Anne Johnson, Professor of Infectious Disease Epidemiology at University College London, who received a damehood in 2013 for her work on human sexuality and, in particular, the HIV epidemic in the 1980s. 'It was revolutionary that he legitimized sex as a legitimate topic for scientific inquiry.' Johnson is one of hundreds of scientists who have tirelessly catalogued British sexual habits with the National Survey of Sexual Attitudes and Lifestyles survey (Natsal) in the UK. Published once a decade (1990, 2000, and the most recent in 2013), these surveys have carried on Kinsey's meticulous mapping of human sexual diversity.

Half a century ago, Kinsey's Sexual Response in the Human Female (1953), the follow-up to his ground-breaking study of the human male, Sexual Behavior in the Human Male (1948), indicated that 10 per cent of women had never reached orgasm in their marital intercourse, but that 40 per cent of women had their first orgasm through masturbation. Kinsey would later conclude that climax through intercourse was the exception rather than the norm, and would pen passionate polemics railing against mainstream ideas that women ought to come through penetration alone.

Kinsey was married but was what would have been called at the time a 'latent homosexual'. This is unsurprising, considering one of his best-known studies measured the distance ejaculate travels. He aimed to address the question of whether or not the cervix actively sucks semen inwards to facilitate fertilization, or if male emissions robustly slam against the cervix, forcing their way inwards. It seemed the answer could be found by measuring the velocity with which human ejaculate travels. To investigate, he paid more than 300 men to masturbate on film. Biographers have revealed that Kinsey's homosexual leanings resulted in much angst: he thrust a toothbrush down his urethra as a teen in an act of self-castigation, and later revealed faecophilic tendencies. He might have been a bit odd, but was undeniably a true humanitarian: he tirelessly fought for the notion that diversity is the norm and championed the importance of direct clitoral stimulation during a time when other post-war sex scientists trivialized it.

A case in point are researchers William Masters and Virginia Johnson – so famed they are known simply as 'Masters & Johnson'.

They took sex research beyond the meticulous categorization Kinsey pioneered and brought it into the laboratory. They were the first to systematically observe couples copulating in the lab, in a sense revolutionizing the study of reproduction. Defending their brave methods, they proclaimed: 'Science and scientists continue to be governed by fear – fear of public opinion, fear of religious intolerance, fear of political pressure, and above all, fear of bigotry and prejudice – as much within as without the professional world.'

However, the pair did many things that today would never pass the ethics committee, such as assigning random strangers to fornicate (modern anatomical studies enlist couples). The report was opaquely titled: 'Persons Studied in Pairs'.

The two initially met in 1957 when Masters hired Johnson, his secretary, to assist him in his research, perhaps because he knew having a female author on his papers would lend his work a greater air of credibility. A man pairing random people to shag in front of him undoubtedly looks a bit suspect.

Masters and Johnson concluded that orgasms in women arise from clitoral stimulation, positing that tugs on the labia and clitoral sheath during penetrative sex deliver the requisite stimulation required for climax. Upside: the clitoris is crucial. However, they poisoned their clitoral chalice by arguing that women who do not climax from intercourse alone suffer from 'sexual dysfunction'.

Nor were they remotely unique in this designation: researchers Edmund Bergler and William S. Kroger defined frigidity as 'the incapacity of a woman to have a vaginal orgasm during intercourse' in their 1954 book Kinsey's Myth of Female Sexuality: The

Medical Facts. Keyword: 'myth'. One can be certain that these two men were just fantastic in the sack.

Other researchers attempted to put forward more helpful suggestions for the possible use of the clitoris in penetrative intercourse. Surgeon W. G. Rathmann describes in a 1959 scientific paper a clamp he devised to remove the clitoral hood to make it easier for fumbling men to find, claiming that one of his patients had 'wasted four perfectly good husbands' by not coming to him sooner.

And if hood removal sounds extreme, consider the extraordinary case of Princess Marie Bonaparte (1882–1962), who opted to have her clitoris surgically repositioned. Twice.

The great-grandniece of Napoleon Bonaparte, Marie was equal parts pioneering sex scientist as well as landmark medical case study. In her lifelong quest to experience orgasm through penetration alone, she sought to locate the anatomical source of her dissatisfaction. Hypothesis: The distance between the clitoris and the vagina predicts the likelihood of orgasm by penetration. Method: Interviews with 243 women, and measurement of their clitoral–vaginal disparity. A stickler for accuracy, she used the urethra as a point of measurement, rather than the vaginal opening itself, as the vagina's precise borders can be difficult to define.

Conclusion: Women come* in three varieties. Luckiest: 'paraclitoridiennes', endowed with clitorises less than an inch divorced from their vagina, which she estimated at 69 per cent of the female population. Most unlucky: 'téléclitoridiennes', with more than an inch of distance to bear, estimated at 21 per cent. The rest: 'mesoclitoriennes'. Declaring herself to be an unlucky member of the téléclitoridienne, Princess Marie asked Viennese surgeon Josef Halban to loosen the earthly bonds of her clitoris by snipping the connecting ligaments and reposition her clitoris closer to her vagina. When the result proved unsatisfactory, she asked Halban to repeat the renovation. Again, to no avail for this woman who elevated climax through penetration alone to such a pinnacle that she underwent the knife – twice – for its achievement.†

The great game changer in the understanding of the demographics of female orgasm came with the famous Hite Report in 1976 by American rogue researcher Shere Hite, who interviewed over 100,000 women, aged 14 to 78.

Her most frequently cited finding: 70 per cent of women do not experience orgasm through intercourse alone, but can do so routinely through masturbation, oral or manual stimulation of the clitoris. This figure continues to hold up as an estimate for female sexual response. Hite's findings were widely celebrated by women of all political stripes for demonstrating that climaxing solely from vaginal penetration is the exception rather than the norm. This brought psychological relief to an entire generation of insecure women (because every generation of women finds something to be insecure about).

It is interesting to note that Hite's methods were deemed by academics to be lacking in statistical rigor. Yet Masters & Johnson, who chose to study only women who climax from penetration alone (already established by Kinsey as a minority in the female population), did not endure equivalent criticism for their statistical sloppiness.

Masters & Johnson also recommended conversion therapy for the treatment of homosexuality, and made a good buck attempting to 'cure' gay men of their fondness for members of their own sex. Proving yet again (and this is a theme we will come back to) that scientists are people, people are flawed, and sometimes smart scientists not only hold asinine beliefs, but frequently do terrible things in the name of 'the truth'.

This is almost certainly more true of the study of sex than any other field in biology (certainly more than any topic in chemistry or physics). Sex is a powerful force, and a deeply personal one. Anything anyone in a position of intellectual authority has to say on the matter is therefore likely to hit a nerve. Researchers therefore frequently approach the field with an axe to grind. Their ideas have a profound influence on what we believe to be 'normal'. But their findings do not always lead to persecution and prejudice. Sometimes they deliver psychological relief and improve the lives of millions.

* Pun intended.

† Bonaparte's fate, however, is benign compared with that suffered by Lili Elbe (1882–1931), regarded as the world's first recipient of a male-to-female sex change. She died a year after her first operation (and a few months after her fifth).