When US Republican Todd Akin declared earlier this week that it is impossible or “really rare” for a woman to become pregnant as a result of a “legitimate rape” because “the female body has ways to try and shut the whole thing down” it wasn’t just the feminist blogosphere that went on high alert.

Republican Presidential nominee Mitt Romney was quick to condemn the Missouri Congressman’s claims as “insulting, inexcusable, and, frankly, wrong,“ while President Barack Obama described Akin’s endorsement of such a view as “offensive”.

He continued: “[Rape] is rape, and the idea that we should be parsing, qualifying and slicing what types of rape we’re talking about doesn’t make sense.”

Various Republicans demanded his resignation or at the least an apology (which he has since issued, qualifying “rape is never legitimate”), though not yet vice-presidential nominee Paul Ryan who with Akin last year co-sponsored a proposed bill that used the term “forcible rape” in an effort to narrow access to abortion (the term was later dropped).

It’s encouraging that even Akin’s fellow travellers have swiftly distanced themselves from his purportedly “scientific” claims; it also seems likely that Akin’s political career may not recover from his “misspoken” assertions.

From an Australian vantage point – where despite Tony Abbott’s past efforts, abortion rarely features as an election issue – the whole furore may strike us as peculiarly American.

Yet the related border dispute about what constitutes rape is hardly exclusive to the United States. Also this week, Independent British MP George Galloway dismissed the rape allegations made by two Swedish women against Julian Assange by rehashing the familiar argument that if a woman had already had dinner with the accused, already invited him back to her house, and already had consensual sex with him, only to wake and find him having sex with her (and without a condom), well, “This is something that can happen … not everybody needs to be asked prior to each insertion”.

And further, even if the allegations made by the two women against Assange were “One hundred percent true, even if a camera captured them, they don’t constitute rape…at least not rape as anyone with any common sense can recognise it”.

Suspect definitions of rape do not only flow from the mouths of men – it was Whoopi Goldberg who defended director Roman Polanski against charges of “rape rape”, to cite one of many possible examples – but the default definitions of Akin and Galloway with their appeals to “science” and “common sense” have their origins in at least two centuries of what anti-rape campaigners have branded “rape myths”.

These myths are powerful because historically they have been espoused by medical and legal authorities, and they’re dangerous because they continue to be pervasive enough for the great majority of rape victims to never report the crimes committed against them. It is this enduring reluctance that should give us pause before we consign Akin and Galloway to the lunatic fringe.

Rape myths are amendable to revision, but the basic assumptions endure, as historian Joanna Bourke traced in her 2007 book Rape: A History from 1860 to the Present. Here we discover that Akin’s “legitimate rape” concept is an updated version of the once medically-supported notion that it was virtually impossible to rape a resisting woman, whose thigh and pelvic muscles were presumed powerful enough to fend off unwanted penetration.

To quote directly from medical textbooks, “it is impossible to sheath a sword into a vibrating scabbard”. Under the terms of this myth, one assailant did not have a chance against a woman determined not to be violated. In Akin’s contemporary reworking of this logic, where the female body is assigned the ability to “shut down” its reproductive capacities during a “legitimate rape”, he also draws on another since medically discredited notion that nonetheless enjoyed long-time popular support: that female orgasm is necessary for conception.

In Galloway’s protracted dismissal of Assange’s accusers, he merged two myths into one rant: women lie and rape is not serious.

Central to each of these myths is the notion that everyday heterosexual acts – where men might get a little “carried away” – are vulnerable to wilful or histrionic misinterpretation by women.

The question of consent is sidelined or repackaged as another myth, “no means yes”, and the burden of proof is placed on the victim to prove otherwise. Under this constellation of assumptions, the only “true” rapist is a stranger, despite evidence that rape by close acquaintances has been on the increase since the mid-twentieth century – that is, since the rise of dating culture and the invention of the contraceptive pill.

Akin and Galloway have hardly gone unchallenged this week – note that the satirists at The Onion cleverly led with a story titled “Pregnant Woman Relieved to Learn Her Rape was Illegitimate” – but as Joanna Bourke reminds us, rape myths circulate daily and widely and have real-life effects.

The general public, or at least those called for jury service, continue to apply a definition of what constitutes rape that is “much narrower than that decreed by law”.

Dr Zora Simic is a lecturer at the School of Humanities at UNSW.

This opinion piece first appeared in The Conversation.