So I understand where you're coming from, but I feel like you're forgetting some pretty big issues regarding this. The first is that this is a monogamous society, somehow, so 1 man is not getting multiple women pregnant. The fact they have to protest for legalized polygamy is something to note regarding that. If 1 man getting multiple women pregnant is socially stigmatized and I have to assume still somewhat is since they have to protest for it rather than it being a simple vote or natural change in their social structure, then they've clearly had it for quite some time.
It has to have been around for generations if it's something that deeply ingrained in society. With this in mind you realize a man is, in general, only going to have 1 lineage. He's not spreading out his genetics like Ghengis Khan, unfortunately.
In a society that practices monogamy, with a 1:5 male ratio, you are very much depending on the male population to keep you alive because most of the women in your society simply won't breed. Period. In modern day, sperm banks exist so that alleviates that issue for the most part but that's only in modern day. It clearly didn't stop the need for a wider spread of genetics if the story is to be believed, so monogamy wasn't created in the advent of sperm preservation. Meaning this root should logically be deeper in their history.
If their societies were anything similar to ours, then monogamy would have been a thing for centuries (you can find monogamy enforced in old babylonian laws, for example). In a monogamous society, with 1 man per lineage, you would very much need to be the dominant force to keep your society alive and to prevent the men from doing anything stupid that could harm their ability to reproduce AND to protect them from violence.
The second issue I think you may be overlooking is that a lot of what makes men protect and build and grow things and even be the risk-takers that we are naturally, all came from the ancestral need to be the protector, the builder, the grower and the risk-taker. Because the men who did these things were often the ones who managed to reproduce.
There's a hypothesis that monogamy started as a way to protect women from being targeted during pregnancy and child raising, because if you had a husband then you had a protector and provider. But they don't have that luxury with how few men there are, they couldn't logically have that, so where does this desire for monogamy come from? If we swap the roles then that means men would have had to be protected from women.
And I think that makes sense because, and I'm sure I've said this before, what's the easiest way to kill off an enemy tribe if they truly have a 1:5 ratio? Kill their men, they'll dwindle to nothing. Or take their men, and you'll bolster your own economy. So from that perspective, women would have to be the dominant force just as a matter of fact. Women would have to be the warriors and frontliners, you couldn't risk men being killed in combat or stolen away, women would likely have to fight for the few male resources available in their own tribes too.
There's really no two ways about this. If you understand the way humans and society evolved, you understand that all that we know and understand as a society today was built as an adaptation to the way life was back then. Like, those instincts and traits didn't die out. We repurposed them for the modern day, but they're still inside you actively functioning to this day.
Flipping the genders and skewing their ratio isn't a small thing in that regard, they're massive. They have knock on effects on quite literally everything. It's not even crazy to say that if things hadn't been how they were, if the conditions of survival were even slightly worse, humanity as a species may very well have died out. Like, there were something upward of 14 species of human and all but ours died because they couldn't adapt and we just barely scraped by too. Yet the story changes 2 of the biggest core concepts of who we are as a species and thinks we can maintain a sense of normalcy like monogamy. It just doesn't work out if you take it too seriously, which I very often do because I like to think and overthink until I can think no more.
I believe you're making some very unrealistic extrapolations from the ideal concept of monogamy to how it plays out in real populations. There's a few points here:
1. In many premodern cultures there simply wasn't an expecation of monogamy. That's mostly a modern, western thing. Examples of polygyny include islamic cultures (vast swathes of everything outside of the European sphere) to east asia. So for societies that don't enforce strict monogamy a 1:5 ratio wouldn't have the effects you describe. The upper class of polygynous cultures probably already have a 1:5 ratio when it comes to sexual partners so the only variable is how the lower class would be structured. So I could totally see men still being socially dominant because the only difference would be that instead of the IRL lower class of 1:1 ratio, you'd have a lower class of an even more extreme ratio than 1:5. To the upper class it wouldn't matter whether their lower class serfs were male or female so you can easily have the same patriarchal dynamics.
2. Even in cultures with monogamy e.g. Christian Europe, monogamy doesn't in practice mean a man only ever reproduce with one woman. And I'm talking about IRL history here. What actually tends to happen is that men have multiple partners by divorce or widowing. Becoming a widow is especially common when many women die in childbirth. So even in monogamous pre-modern cultures you'd have men who have like 3 wives (not concurrently) throughout their lifetimes if they manage to survive, which is more likely if you're rich and powerful. Which is also one of the reasons that men are incentivized to be risk takers. They have a higher ceiling for payoff.
3. Women are only usefully fertile for at most 2 decades in practice (highest fertility starts at age 18 and goes steeply downhill from there), especially before modern medicine. Rich old men are easily fertile into their senior years until the day they die. If your society has a 1:5 ratio and has monogamy but also allows divorce, you'll probably see a lot of men divorcing after their wives pass the fertile age.
4. So in a fictional 1:5 version, even with something like Christian monogamy, you could still have the men mating with enough women in practice via premarital sex, outliving their wives, divorce, or affairs. Affairs and premarital sex were so common historically even in the IRL 1:1 world that there'd be a whole social class of bastards in many premodern societies. In a 1:5 world where the women are hornier they could easily compensate by initiating more of that.
In general I think you're arguing against well established literature that women are the reproductive bottleneck in human societies, not men, and therefore a 1:5 ratio wouldn't necessarily change much. Not that it cannot, but it doesn't have to. There are also other reasons to think that the ratio may actually benefit men's domination. They hold a valuable resource that scales as much as they wish (unlike a sex flipped version, because female reproduction doens't scale). With more females, the demand goes up, so it actually gives them more leverage, which potentially could be turned into social capital. I can easily see how, if the author wished it, they could argue that men secured a dominant social position by being kingmaker (queenmaker?) by default in every social contest among women.
Imagine if tribal negotiations came down to whether your tribe could secure those breeding males for use by your Queen and her elite guards. The male is more valuable if he's at least somewhat willing, since we wouldn't have artificial insemenation until the modern era, so you can't just milk him once and pass the stuff around. This could produce a tribal environment where males get more leverage and this leaves downstream impacts on human culture.
Like, we haven't been given a history lesson in this series so the author could actually go with whatever they like if they choose to reveal some world building in later chapters. I don't think it's fair to say that they CAN'T. We can't rule out that the author just comes out and reveals that Japan's history in this 1:5 world is different from IRL history and they have a long tradition of polygyny that only got banned by the Americans post-war. Hell, perhaps monogamy was basically a population-control economic sanction the Allies imposed on Japan. Since it's fiction, there's all sorts of possiblities.
And as an aside, the best social science explanation for IRL monogamy as an institution is for the benefit of the men, not women. Monogamy is a kind of rationing of women for the men. Without it, the elite males take multiple wives and creates social friction with a bunch of maidenless young men who are likely to form warrior bands and start revolutions that topple the social order. Of course, this wouldn't be a problem in the 1:5 world...
Last edited: