Eternal Sexual Freedom

""Each generation thinks it has invented sex, Nuala, and is shocked and not a little displeased to discover that its predecessors enjoyed it too.""

- Andrew M. Greeley's "Irish Gold"

Times change, and so do sexual mores, but you wouldn't know that from most modern historical fiction. While it's certainly true that people have had premarital sex, extramarital sex, and even gay sex since the beginning of time, doing so (or at least getting caught) was, in many time periods, a Very Bad Thing. However, some writers of period fiction don't seem to realize this and thus their character behave as though contemporary sexual mores (or even looser ones) exist in their historic worlds.

This isn't to say that sex shouldn't happen in period fiction; on the contrary, sex happened a lot, it was the attitudes about sex and its results that differed. For example, there's nothing historically inaccurate about a story set in Topeka in the 1930s about a married man having an affair. But if the mistress has his child, and everybody is perfectly fine with it, the woman isn't shunned or gossiped about, and the child is acknowledged openly as his son, then it would fall right into this trope. Put another way, it's not so much what the characters do as how it's treated by the other characters.

The only way to avoid this trope is to Do The Research on the time and place in which the work is set: attitudes toward pre- and extra-marital sex and illegitimacy varied widely from class to class, time period to time period, and country to country. And then use the trope Deliberate Values Dissonance as needed.

Writers can also err when they show couples enthusiastically partaking in forms of sex more common now than in other time periods. Oral and anal sex and various mild kinks that are now viewed as perfectly acceptable may well have been regarded as completely depraved in the time and place the work is set. Though some historians claim anal sex was popular in some cultures as a form of birth control.

Because this is a subtrope of Did Not Do the Research that applies to historical accuracy: it doesn't apply to fantasy settings, Alternate History works, works set in the future, or works set in the present day.

See Everybody Has Lots of Sex for the setting most commonly invoked by this trope.

Advertising

 * Subverted humorously in a recent Carl's Jr./Hardee's TV commercial in which a man in a suit, having apparently time-travelled from the antebellum South, shows up on a beach in the present day with a picnic basket full of Carl's/Hardee's new made-from-scratch biscuits. After sharing his biscuits with the shorts- and bikini-clad beachcombers, the first thing he wonders is why everyone is in their underwear.

Anime

 * In Samurai Champloo it's actually Lampshaded in one episode by the narrator reminding that Edo-period Japan had different sexual mores from the later Meiji-period when the Western influences started to creep in. Calling it more "liberal", however, would be simplistic—sure, homosexual relationships were tolerated and even valued. But rape was often used as a punishment or interrogation method on female criminals, pederasty was widespread and even encouraged, and the main reason homosexuality was accepted was misogyny (because why would you want to love a mere woman?).
 * Played with in Victorian Romance Emma, what with the servant girls talking openly about their sexcapades and German immigrant Dorothea standing by a hotel window stark naked. Then again, this could be a subversion of Victorian sexuality, given how hypocritical it actually was.

Comic Books

 * Lampshaded in The Ultimates volume three; it's set in the 21st century and when the implied and mostly humorous Brother-Sister Incest between Quicksilver and Scarlet Witch was made explicit, Wasp chastised Captain America's "1940s brain" for being unable to comprehend it. And as Cracked.com's The 6 Creepist Comic Book Characters of All Time put it: "we are quite sure incest existed back then, too."
 * Not to mention, they were rather a bit more lenient back then on some of what we would call incest now. Brother Sister incest was as unacceptable then as it is now, but first cousins married sometimes. It's still legal in many places.
 * More to the point, why was the Wasp talking as though brother-sister incest is considered normal or acceptable nowadays?

Film

 * The 1995 version of The Scarlet Letter imposes this trope on the Puritans, of all people, by portraying the main characters as feeling guiltless over their adultery. Roger Ebert breaks down just how far afield from the source material the film goes.

Literature

 * The Shadow In The North provides one example. When Sally's friends seem perfectly thrilled she's got knocked up outside marriage and don't even seem to worry this might be difficult for her.
 * However, in the next book The Tiger In The Well this turns into a huge problem for her when a fake husband turns up and hardly anybody is willing to believe Sally's side of the story. Possible Author's Saving Throw?
 * Averted in Robert A. Heinlein's Time Enough for Love. While main character Lazarus Long travels back to 1916 and has copious sex with his mother, and they seem to have no issues with what they're doing, they both put a lot of effort into making sure the relationship appears chaste and wholesome to anyone else. The part where they're banging like bunnies is kept secret from others. Additionally, she knows that she is already pregnant from her husband, so she does not have to worry about contraception. Of course, Parental Incest was just as unacceptable when Heinlein was writing as it was in 1916.
 * Diana Gabaldon's Outlander series does a pretty good job of subverting this in a historically appropriate manner, even if the books do involve a good bit of time travel. In one of the later books, . And the heroic homosexual character "coming out" is Squick to the heroine, equivalent to him confessing to murdering puppies.
 * Justified in Freedom and Necessity by Steven Brust and Emma Bull: Susan and Kitty's rather modern sexual mores are Hand Waved away—they're eccentric radical bohemians, and rather wealthy, so they are in a position to ignore "normal" 19th-century concerns about extra-marital sex, or being women living alone. Susan does comment that, having (chastely) sat up with a man overnight, her reputation would be gone if anyone knew about it.

Live Action TV

 * In the second episode of New Amsterdam, during a flashback set in the early 1940s, John produces a baby apparently outside of wedlock and no one cares. Lily was fired after her employer saw her with a white man and she had to enter the hotel through a service elevator. Her father was very upset with them both, and said they could never make it in the world. The hotel staff react more reasonably than you would expect in real life in the 1940s, but they may not have known John and Lily were together. Lily herself breaks it off, knowing they'll be together in the long run. It turns out this after she gets pregnant, and when they reunite in the black hospital, there are some very pointed looks.
 * M*A*S*H plays with this trope several different ways, depending on the character and the writer(s) of the episode. For the married Trapper John, and early-season bachelor Hawkeye Pierce, Eternal Sexual Freedom is in full play; no one calls them out on their open and casual affairs. The married Frank Burns, on the other hand, is treated like scum for establishing an ongoing, if shallow, relationship with Margaret Houlihan, who gets the nickname "Hot Lips" out of it. B.J. Honeycutt, on the very rare occasions that he isn't completely faithful to his wife Peg, receives a reaction somewhere between disappointment in his behavior and anger for Peg's sake from the other characters.
 * That '70s Show: Some of the show's later plots, while not actually incorrect, were very unlikely to happen, such as Hyde marrying a stripper and continuing to live with the Formans, or Eric and Donna getting caught having sex in the kitchen and suffering no repercussions. In all likelihood, those things wouldn't happen now.
 * Averted in the Torchwood episode "Out of Time"—the temporally-displaced characters have to be told about modern sexual mores, and each reacts differently.
 * The Doctor Who two-parter "The Empty Child"/"The Doctor Dances" provided a couple of nice subversions: first by having Nancy get out of a tight situation by calling a man on his homosexual activities, then dealing with her own shame at the revelation that Jamie was not her brother, but her out-of-wedlock son.
 * Rome was filled with sex and violence, supposedly historically vetted. But while the show prides itself on well-researched use of Deliberate Values Dissonance, it also makes a few mistakes. For example, oral sex, referenced frequently with its western connotations, was considered vulgar and disgusting by the otherwise-licentious Romans.
 * Partly averted on an episode of Foyle's War with a gay, WW 2-era RAF pilot. He feels a great deal of Gayngst and has to stay closeted because he knows that if it gets out, they'll never let him fly another mission. He tries to get a girl to be his beard, but she's disgusted by him. It's a clever episode because the audience can see the tragedy of his situation without any Author Filibuster pointing it out. Still, it's only a partial aversion because Foyle himself, being the saintly gentleman that he is, has absolutely no problem with the fact that this guy is madly in love with Foyle, Jr.

Newspaper Comics

 * In 9 Chickweed Lane, during the extended WWII flashback arc, Edna (a younger Gran) and her ex-POV lover Peter Kiesl got into Public Displays of Affection that, while perfectly in line with the strip's usual tone and would probably get them no more than a call of "Get a room," would get the cops called on them in 1950s' New York City.

Video Games

 * In Tropico 3, you can legalize same-sex marriage... in the 1950s. Granted, the Cold War is grafted on to an island with mostly 1980-2010 sensibilities anyway.
 * In The Sims Medieval no one seems to object to premarital sex, promiscuity or same-sex relationships...in the Middle Ages. On the other hand, as wizards are an accepted and in fact normal part of medieval life and women can have any profession they want in a time period when women were merely house wives, its fairly obvious the game is taking more than its fair share of creative license with the era.