Sexology is the scientific study of human sexuality, including human sexual interests, behaviors, and functions. The term sexology does not generally refer to the non-scientific study of sexuality, such as social criticism. Sexologists apply tools from several academic fields, such as anthropology, biology, medicine, psychology, epidemiology, sociology, and criminology. Topics of study include sexual development (puberty), sexual orientation, gender identity, sexual relationships, sexual activities, paraphilias, and atypical sexual interests. It also includes the study of sexuality across the lifespan, including child sexuality, puberty, adolescent sexuality, and sexuality among the elderly. Sexology also spans sexuality among those with mental or physical disabilities. The sexological study of sexual dysfunctions and disorders, including erectile dysfunction and anorgasmia, are also mainstays. History Early Sex manuals have existed since antiquity, such as Ovid's Ars Amatoria, the Kama Sutra of Vatsyayana, the Ananga Ranga, and The Perfumed Garden for the Soul's Recreation. (Prostitution in the City of Paris), an early 1830s study on 3,558 registered prostitutes in Paris, written by Alexander Jean Baptiste Parent-Duchatelet (published in 1837, a year after he died), has been called the first work of modern sex research. The scientific study of sexual behavior in human beings began in the 19th century with Heinrich Kaan, whose book Psychopathia Sexualis (1844) Michel Foucault describes as marking "the date of birth, or in any case the date of the emergence of sexuality and sexual aberrations in the psychiatric field." The term sexology was coined for the first time in the United States by Elizabeth Osgood Goodrich Willard in 1867. Roughly simultaneously a group of homophile activists, not yet identifying themselves as sexologists, were responding to shifts in Europe's national borders, a crisis that brought into conflict laws that were sexually liberal and laws that criminalized behaviors such as homosexual activity. Victorian era to WWII Despite the prevailing social attitude of sexual repression in the Victorian era, the movement towards sexual emancipation began towards the end of the nineteenth century in England and Germany. In 1886, Richard Freiherr von Krafft-Ebing published Psychopathia Sexualis. That work is considered as having established sexology as a scientific discipline. In England, the founding father of sexology was the doctor and sexologist Havelock Ellis who challenged the sexual taboos of his era regarding masturbation and homosexuality and revolutionized the conception of sex in his time. His seminal work was the 1897 Sexual Inversion, which describes the sexual relations of homosexual