Homosexual seduction was a historical sexological theory suggesting homosexuality was being spread through intergenerational sex, and older homosexuals were changing the sexual orientation of previously heterosexual youth by seducing them.
The theory originated in the early 20th century's work of German psychologists such as Albert Moll and Emil Kraepelin on adolescent sexuality, and was used in the early work attempting to explain the phenomenon of male prostitution. It played an important role in population regeneration efforts after the First World War in Germany and informed homophobic policies at the time. 
In the 19th century, German psychologists Magnus Hirschfeld and Karl Heinrich Ulrichs both argued for the inborn nature of homosexuality. 
Challenging the idea of inborn and fixed sexuality, Sigmund Freud theorised that humans were inherently bisexual, and then became either heterosexual or homosexual as a result of childhood experiences. Freud argued that same-sex attraction and experimentation were essential parts of development, with heterosexuality being the preferable outcome. Although he argued that homosexuality should not be thought of as an illness, his focus on how the social environment may shift sexual identity inspired theories behind homosexual seduction.  
Opposing the inborn nature of sexuality put forward by Hirschfeld and Ulrichs, other psychologists including Max Dessoir, Albert Moll and Emil Kraepelin built on Freud’s conception of teenage sexuality as indeterminate and susceptible to social influence. They recognised that same-sex activities such as kisses and hugs formed an integral part of development, but these acts should stop as young people come of age. They argued that if vulnerable adolescents came in contact with same-sex seduction, homosexual attraction might become permanently fixed. Therefore, the science at the time painted homosexual seduction as a danger to young people. 
As is the case with any scientific venture, these ideas were historically situated. In Germany in the 1920s, there was concern about the First World War’s detrimental psychological effects on men. The possible spread of homosexuality posed a threat to marriage and childbirth, which were both perceived as essential aspects of the regeneration of post-war society. Therefore, scholarship produced at the time aimed to prove that homosexuality was a threat to the regeneration of society but its spread can be stopped. This served to justify homophobic measures by the state such as eliminating 'gay propaganda' and introducing prison sentences for homosexual teachers that came into contact with youth. 
The theory has subsequently been used in homophobic propaganda and LGBT rights opposition to delay the progress of LGBT rights, by villainizing homosexual men as "old perverts who prey on children". The theoretical link between homosexual men and predation has permeated discussions about levelling the age of consent, anti-discrimination efforts and created harmful stereotypes around gay men.
The idea that homosexuality was spreading through intergenerational sex was one of the main reasons behind the oppression and killing of homosexual people in Nazi Germany. Since organisations such as the Hitlerjugend and the SS mostly comprised young men, the government cracked down heavily on ‘moral corruption’ as part of the Night of Long Knives and the Holocaust. 
The theoretical link between homosexual activity and predation heavily influenced the LGBTQ+ community’s battle for equal rights as well.
In the United Kingdom, the 1976 Sexual Offences Act partially decriminalised homosexuality, but set the homosexual age of consent at 21 years of age as opposed to 16 for heterosexual people. The rhetoric around the issue often involved politicians constructing young people as vulnerable to homosexual seduction. For example, politicians argued that “sixteen is an extremely formative age....at 16, young people ... are unsure about themselves”  (Earl Ferrers), and “those extra two years may well save [a boy] from becoming involved in a homosexual relationship which he might bitterly regret later in life”  (Lord Gray of Contin). Subsequently, the homosexual age of consent in the United Kingdom was made equal to the heterosexual age of consent in 2000.
In the United States, Anita Bryant ran a successful campaign espousing the ideas behind homosexual seduction theory to get openly gay teachers banned from working in public schools in some states and to overturn anti-discrimination policies in others. Other famous people and organisations that were influenced by homosexual seduction theory include Judith Reisman, Paul Cameron, the Traditional Values Coalition and the Abiding Truth Ministries. 
The idea of homosexual seduction is often connected to arguments about homosexual men being more likely to engage in paedophilia and child molestation. This idea has been debunked multiple times in psychological academic discourse.   Research has also shown that people possessing negative attitudes towards homosexuals are more prone to believe that homosexuality is the result of social influences, such as early sexual experiences. 
The current scientific understanding of the causes of homosexuality contradicts the majority of the arguments of homosexual seduction theory.
Numerous studies have found that, in almost all cases, homosexual attraction precedes sexual activity in young people, not the other way around.  
Moreover, there is overwhelmingly more evidence for the non-social attributes of sexual identity than social causes - notwithstanding that sexual orientation certainly is influenced by the environment. However, scientific evidence for the most commonly believed social causes of homosexuality is mostly weak in magnitude and is warped by several confounding factors, and no causal theory of sexual orientation has garnered universal scientific acclaim as of now. 
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