This idea came to me after reading up on the relationships of the prairie vole and the research done into why monogamous pair-bonding occurs. What I'm looking for in my story is biologically enforced sexual monogamous pair-bonding, and how science could stop it. People in pair bonds do not have to be in love, and in fact being pair-bonded does not mean you will love your partner necessarily, only that you are only sexually attracted/can mate with them. (for more context on the worldbuilding, look to the end of the post)
The Research so far
So the closest animals I could find that were sexually and socially monogamous seem to be the prairie vole's. One article has this to say about biological reasons for what causes the pair bonding:
Several studies have now demonstrated that oxytocin plays a role in the development of the pair bond in the female prairie vole. Injections of an OT antagonist, a drug that blocks activation of the OT receptor, directly into the female prairie vole brain prior to cohabitation and mating inhibits the subsequent development of a partner preference (Insel and Hulihan, 1995). Some studies have suggested that OT's role in partner preference formation is specific only for females, while other studies have found similar effects in both sexes (Cho et al., 1999). However, in males there is clear evidence that the peptide arginine vasopressin (AVP) plays a significant role in the formation of the pair bond of the male for its mate.
I'm not a biologist so I don't really totally understand everything in the linked article, but essentially what I got out of it was that mating between two specific prairie voles lead to changes in their brain chemistry - the release of OT and AVP - while around their preferred partner. Essentially 'love is a drug' and this causes them to seek out that preferred partner who gives them more OT or AVP. This is more 'emotion based' than I am looking for, but I think it's a good start maybe?
I'm not sure if prairie voles can be considered entirely sexually monogamous, however, as there have been studies that prove the genetic offspring is sometimes fathered by a male outside the pair bond:
For biologists, monogamy implies selective (not exclusive) mating, a shared nesting area, and biparental care. In recent years, genetic analyses of offspring have provided evidence for extra-pair copulations even among species thought to mate exclusively monogamously.
The incidence of sexual monogamy appears quite rare in other parts of the animal kingdom. It is becoming clear that even animals that are overtly socially monogamous engage in extra-pair copulations. For example, while over 90% of birds are socially monogamous, "on average, 30 percent or more of the baby birds in any nest [are] sired by someone other than the resident male."
Based on this, I'm not even sure if there are any existing species that are entirely sexually and socially monogamous. If there are and I just haven't found them, please let me know (if there's research on it anyways) what allows them to be sexually and socially monogamous on a biological level. Additionally: how could such enforced monogamy be broken with science?
For more context, this is my worldbuilding that I'm trying to back up with science:
World has late Victorian/early Edwardian era level of technology and scientific advancement (if needed I could come up with some reason they have more advanced science though). The people are essentially humans except for the changes needed to be made for sexual monogamy/pair bonds to work (aka if I need to give them the ability to smell pheremones or something I will but otherwise they are just human). All men and women are thought to be 'incomplete' before they bond with someone, as the Creator made men and women together as two sides of the same coin/soul but seperated them at birth. Only once they become one once more are they 'whole.'
As soulmates are 'ordained by the creator' only the church can know who is truly meant for who, as they are the voice of the creator. In reality bondings are done for political or socio-economic reasons, though there is a lot of romanticisation of 'falling in love at first sight' like in our world. (fun fact: the church is always lead by a pair-bonded priest and priestess. They give up any children they have to the church to become men/women of the cloth where they are raised communally. There is no prohibition of sex or having children within the church.)
Bonding happens upon consummation of a union (sex/mating) and from that point on it is impossible for the two to have sex with anyone else - meaning they will not be sexually aroused by anyone else or physically attracted to someone else and cannot bond with someone else. It does not mean that they necessarily will be attracted to the other person, only that they can only be attracted to them. By this I mean that men can still have ED and women can still not have fun in the bedroom if their bonded sucks at sex. The only way for anyone to bond with someone else is for their bondmate to die.
The story is about a woman activist who finds herself in a very unhappy bonding and wishes to find some way to break it without killing her bondmate and going to jail for murder.
- what biologically could cause complete sexual monogamy within a pair-bond? I'm not looking for cultural norms, but rather a biological reason for why a bonded pair would only be able to mate with one another after having sex.
- what scientifically could break or reverse such a biological pair bond?
Bonus points for helping me with these questions too:
- whether pair-bonding has to be tied to orgasm during mating.
- how this biological pair bonding would affect sexual aggression.
- how this biological pair bonding would apply to LGBTQ attraction.