Whenever, wherever on this earth, we will find people who contravene gender boundaries. I'm not talking about the small ways of 'queering' gender, such as the lesbian separatists who wore dungarees in the 1970s. I mean the big ways: not just queering gender, but crossing gender. I mean the drive that makes people risk so much to represent a gender they feel is theirs, and yet is very different to the social, cultural and legal expectations of their birth sex. Whatever culture, country or epoch you choose to research, you will find a history of individuals who, if they lived now, we might now refer to as trans people.

We must be careful with our words. 'Transvestite' originated in 1910 from the German sexologist Magnus Hirschfeld, who would later develop the Berlin Institute where the very first 'sex change' operations took place. 'Transsexual' was not coined until 1949, 'transgender' not until 1971, and 'trans' (a very British term) not until 1996. According to the Oxford English Dictionary, the first use of 'androgyne' was recorded in 1552, but it has only been in the last 10 years that people have claimed it for themselves to describe a state of being in-between, or having both genders. 'Polygender' is a late 1990s Californian invention used to describe a state of being multiple genders.

This is by no means a complete list of words used by people to describe themselves. Long before Hirschfeld, other cultures had developed their own terminologies to describe 'trans' people. From the Hijra of India, to the Fa'afafine of Polynesia, the ladyboys and the tomboys of Thailand, and the Takatāpui of New Zealand, there are a myriad of words used by trans people to describe themselves.

The start of the scientific study of sexology

In 1885 the Criminal Law Act was passed in the UK, which made all homosexual behaviour illegal. Similar laws were put in place throughout Europe during this period. When homosexuality was made illegal, those suspected of it - such as Oscar Wilde - could face imprisonment and hard labour for up to two years. People who cross-dressed became easy targets of the law because they were associated, in the public mind, with homosexual subculture.

One of the first public trials for transvestite behaviour was that of Ernest (Stella) Boulton, and Fred (Fanny) Park, arrested in 1870 for indecent behaviour. The authorities based the prosecution on their transvestism and their soliciting of men as women, rather than the act of sodomy. No conviction could be obtained on these grounds and they were acquitted of the charge of conspiracy to commit a felony by cross-dressing. One of the largest organisations for transvestite men in the US today is the Boulton and Park Society.

As a result of these laws, people who were trans sought out doctors who could cure them and a whole new field in medicine developed: sexology. The first sexologist who took a special interest in the sexual impulses of trans individuals was probably Krafft-Ebbing (1840-1902), professor of psychiatry at Vienna. His Psychopathia Sexualis was published from 1877 to after his death. Krafft-Ebbing constantly endeavoured to give clearer classifications to the behaviours and individual histories of his patients.

Through the work of the early sexologists such as Krafft-Ebbing and Hirschfield, transsexuality became a recognized phenomenon available for study, discussion and treatment. Throughout the 1920s and 30s medical provision was very sparse, but still transsexual people managed to find doctors who would help them. At Hirschfield's infamous clinic, the first sex change operations were performed by Dr Felix Abraham: a mastectomy on a trans man in 1926, a penectomy on his domestic servant Dora in 1930, and a vaginoplasty on Lili Elbe, a Danish painter, in 1931. The surgery was not easy, and Lily died less than two years later from complications.

In the UK, Michael (formerly Laura) Dillon managed to obtain gender reassignment treatment during the war. In the late 1940s he even had a penis constructed by the plastic surgeon Sir Harold Gilles, who later became famous for his work with burns victims. Michael Dillon trained and worked as a ship's doctor until he was outed by the Sunday Express in 1958. He withdrew to India where he became a Buddhist monk and writer until his death in 1962.

Modern transsexuality

Eight years before Dillon was outed, Christine Jorgensen, a former American GI, returned from Denmark where she had undergone the first of several operations as part of her gender reassignment, and the media picked up on the story. Overnight she became a news sensation, and was undoubtedly the most famous transsexual figure in the 20th century. She was beautiful, blond, and everybody's idea of the 'all-American girl'. As one obituary put it:

"Her very public life after her 1952 transition and surgery was a model for other transsexuals for decades. She was a tireless lecturer on the subject of transsexuality, pleading for understanding from a public that all too often wanted to see transsexuals as freaks or perverts ... Ms Jorgensen's poise, charm, and wit won the hearts of millions."

[Candice Brown Elliot, 1999]

Almost immediately, Jorgensen's psychiatrist in Denmark, Dr Hamburger, started receiving letters and in 1953 he published a paper, The desire for change of sex as shown by personal letters from 465 men and women. Suddenly medical professionals realised that these were not exceptional cases: there was a whole swathe of people who were unhappy because their gender role did not match their body.

The endocrinologist Harry Benjamin (who had trained at Hirschfield's clinic) set up a clinical practice, first in New York and later in San Francisco. He trained a new generation of psychiatrists and psychotherapists in the treatment of transsexual people. The former head of research at the UK Gender Identity Clinic at Charing Cross hospital, Professor Richard Green, trained with Benjamin. When Benjamin published the first major textbook on the subject, The Transsexual Phenomenon, in 1966, gender reassignment was still the subject of extensive social stigma both publicly and in the medical world.

Over 40 years later, some of that stigma remains, but it is widely accepted that the only successful treatment for transsexual people is hormone therapy and surgical reassignment. A 1999 appeal court decision in the UK has confirmed this view, and it is an area of medicine that is gradually gaining respectability.

Transsexual people have also become much more visible. Jan (James) Morris, the travel writer, was the Times reporter on the 1953 expedition that conquered Everest; Billy (Dorothy) Tipton was one of the best jazz saxophonists of the 1950s; Wendy (Walter) Carlos is famous for her Switched on Bach recordings. And, of course, many of us now know a trans colleague, neighbour, family member or friend.