Let me know if this is too broad a question. I'm open to book recommendations, too, if this is too broad a topic and a book or two covers it nicely.
My understanding is that early Christianity was part of the Roman empire, which was relatively open about sex. At some point, that obviously changed and morphed into the restrictive evangelical viewpoint seen in American today. Was it a particular Vatican council? Something to do with the Protestant reformation? General cultural influence? Gradual change over time?
Thanks!
To complement /u/AnnalsPornographie points:
Early Christianity exists in the Roman Empire, but it also exists outside the Roman Empire. However, early Christians don't embrace Greco-Roman ideals wholeheartedly. They inherit from Judaism a view of "Gentiles" as basically sexually permissive, and a view of sex that strongly advocates for a sex-within-marriage-only position. I think it's misleading to call this 'anti-sex' in itself. It's certainly what we think of as socially conservative, but that has more to do with 21st western liberal values.
Early Christians, certainly through to the early middle ages, are marked by adherence to those sexual norms. It's a social marker of allegiance to the Christian faith, over and against contemporary social practices. That doesn't mean it was always and everywhere so, but at least generally.
I think you get a shift that begins to take place when the Empire as a whole 'Christianises'. What happens when "everybody" is Christian? You get more of a gap between 'idealised religion' and 'what people do'. And that clearly plays out in the Middle ages and up to the reformation - a disjunct between 'official' religious teaching, and actual practice of religion by the wider population.
I should backtrack, and sa that from the 2nd century onwards there is a strand within Christianity that can be rightly termed 'anti-sex'. This comes with the association of sex itself with sin, but also with the value placed on virginity not just as a pre-marital condition, but as a spiritual state of value in itself. That idealisation combines and interacts with ascetic and martyr ideals in Late Antiquity, and strongly shapes the emergence of monasticism from the 4th and 5th centuries onwards.
The Protestant reformation revived some of that early enthusiasm for sexual conservatism and "realigned" religious practice with religious ideals within Christianity, and this remains relatively strong among groups low in nominalism and high in 'enthusiasm'. Which partly explains modern American evangelicalism, in which you tend to get lower levels of nominalism, as well as a strong adherence to codes of social conformity. But this lacks the anti-sex motif from monasticism, which was reacted against strongly in the Reformation. Socially conservative, yes, but not anti-sex itself.
This is an excerpt from my book that addresses this:
Between the death of Jesus and the 1500s, church leaders had developed a curious array of sexual regulations; more or less a blend between the Greco-Roman and Judeo-Christian ideas. One historian, Keith Thomas, described European sexual morality as "a complex assemblage of pagan and Jewish purity regulations, linked with primitive beliefs about the relationship between sex and the holy, joined to Stoic teachings about sexual ethics and bound together by a patchwork of [new] doctrinal theories."
Both Stoic and Hebrew thinkers, in general, distrusted sex and saw it as a corrupting and defiling pleasure. Stoics saw it as disturbing to an ideally calm and 'stoic' mind, and the early Jews had dozens of purity laws and taboos around sex. When these combined, they could be quite formidable—Saint Paul, for example, argued "I would that all men [and women] were [chaste like] myself it is good for them if they abide even as I. But if they cannot contain [lustfulness], let them marry: for it is better to marry than to burn." (I Corinthians 7.1-40). Saint Augustine also saw lust as evil: "it intrudes where it is not needed and tempts the hearts of faithful and holy people with its untimely and wicked desire. Even if we do not give in to these restless impulses. . .[we would] want them not to exist in us at all, if that were possible."
As a result, marriage and the rules and regulations surrounding marriage became one of the church's primary concerns. Between 1100 and 1300, the church tried to discourage concubinage (multiple sexual partners) and loose moral standards among both the upper and lower classes, with greater or lesser success. Surviving records of the English Church courts indicate that sexual and marital cases made up 60-90% of all litigation—the same holds true in France and elsewhere. Although this control was somewhat successful successful in many places, one of the places it was notably completely unsuccessful was in Rome, the capital of the church and the center of the Christian world. This is something that was frequently satirized and mocked by humanist reformers such as Boccaccio and, of course, Aretino.
The topic of sex was a key issue in the Reformation, and how it changed the face of European life. The Catholic Church’s permissive attitude to sexual morality and prostitution was of major concern to Protestants. Indeed, asAs historian Faramerz Dabhoiwala notes in his Origins of Sex: “Its priests were lecherous parasites: the ideal of clerical celibacy was no more than a joke. [Church] courts were not nearly fierce enough in pursing sexual offender and punishing their moral sins. . .”
Sources for this section include:
Of these, the last one, Dabhoiwala's book does the most to address your question and the development of Christian anti-sex morality or aggressive moralism.