How would the world be affected if only men carried the "magic" gene?

[Sharad9]

In this world, families are generally based around clan systems, with clan mothers being at its head. Exogamy is practiced among families, in which people marry into clans rather than one individual. Men are primarily chosen to marry into clans, often to secure alliances or trade deals between families. Women sometimes join other clans by being adopted into them.

Magic is exclusive to women in this world. However, only men carry the gene that allows magic to be possible. The strength of this gene determines the potential power of the magic user, although other things like training play a role. For this reason, men with the strongest genetic makeup are highly valuable, and are used to unite families or forge alliances similar to how princesses were treated in the middle ages.

How would this affect the role of men in society and culture? Would this lead to inbreeding or genetic deformities, or bottleneck populations?

[PopeLinus1]

Maybe a reverse of normal standards? Or possibly something like the drow society.

[Lvl 2 Expert]

Magic is exclusive to women in this world. However, only men carry the gene that allows magic to be possible.

How do you mean that? I'm guessing you mean women have the gene but can't pass it on right, everybody gets the gene from their father? Or can they pass it on, but only to their sons?

[jqavins]

I'm shooting from the hip, so don't imagine that my responses are authoritative. Preface every statement with "It seems to me..."

Magic is exclusive to women in this world. However, only men carry the gene that allows magic to be possible.

Assuming the real world simplified inheritance rules we learned in high school, this is not possible. To be inherited only from fathers, a gene must reside on the Y chromosome. But females don't get the Y, so such traits can only be passed to sons. I therefore conclude that inheritance works differently in your world, and that will probably have consequences that are farther reaching than just magic ability. What those consequences would be, I can't even try to guess without a model of how inheritance does work in your world. If you'd provide a model then I and others could take a crack at it, but it'll probably be impossible to be thorough.

How would this affect the role of men in society and culture? Would this lead to inbreeding or genetic deformities, or bottleneck populations?

The role, we've discussed to a degree in your previous thread asking "what would make males valuable in a world run by witch covens?" I assume they have greater physical strength than women, because that's part of what people usually mean when talking about men's and women's roles. They may also be better at certain types of labor that don't require such strength. They are the partner in a marriage (or the members of a clan) who are not expected to practice magic and are therefore free for other duties. Etc.

As for inbreeding, this would lead to a tendency toward it, but the outcome would depend very greatly on the cultural taboo against inbreeding, if any. The taboo makes sense from a cultural evolution point of view, assuming the inheritance rules create the same problems that they do IRL. But the strength of the taboo would be influenced by other factors as well, such as the clan structure, the types and strength of religious institutions^*, and so on. So the desire to keep powerful bloodlines pure would compete with the need for genetic diversity, and you could end up with anything from zero inbreeding to the European royal family (note, I did not write "families") to the Targaryens. So, in other words, you're asking how this would affect the society, and the answer is that it depends to a very great deal on the other aspects of the society it is affecting.

I don't see how this would lead to bottlenecks, but it does mean that if a bottleneck occurs then the fraction of the population with magic could (probably would) either drastically increase or drastically decrease, depending on who is alive in the bottleneck. Of course, that also depends on the rules for inheritance.

* Religions are themselves shaped by the forces of cultural evolution, and so are subject to many of the same factors that affect the anti inbreeding taboo directly, but not only those, and not necessarily all of those.

[Sharad9]

How do you mean that? I'm guessing you mean women have the gene but can't pass it on right, everybody gets the gene from their father? Or can they pass it on, but only to their sons?

that is what i mean yes. everyone gets it from their dad, but only men can pass it along.

[jqavins]

that is what i mean yes. everyone gets it from their dad, but only men can pass it along.

Now I'm even more confused. If "everyone gets it from their dad" then everyone has it. So all women have it and all men can pass it on, so there's nothing special about it.

[Lvl 2 Expert]

Now I'm even more confused. If "everyone gets it from their dad" then everyone has it. So all women have it and all men can pass it on, so there's nothing special about it.

Some people get a no magic or low magic variant of the gene, some people get a high magic allele. Or even multiple copies of the gene.

As for the inheritance rules: birds have the opposite version of our sex genes, males have two of the same ones, women two different ones. So maybe these people have that version.

[jqavins]

As for the inheritance rules: birds have the opposite version of our sex genes, males have two of the same ones, women two different ones. So maybe these people have that version.

This I did not know, but I don't think it fixes the problem, at least not by itself. In any case, I don't want to put forward my solution unless Sharad9 asks for it, as I'd like to see what he/she has up his/her sleeve first.

[Sharad9]

This I did not know, but I don't think it fixes the problem, at least not by itself. In any case, I don't want to put forward my solution unless Sharad9 asks for it, as I'd like to see what he/she has up his/her sleeve first.

So what if only fathers' can pass it on to their sons? Does it work better?

[brian 333]

A Wizard Of Earthsea comes to mind.

[jqavins]

So what if only fathers' can pass it on to their sons? Does it work better?

Well, for some time you've been talking about this world where only women can be casters, and I thought that part was carved in stone. A simple patralineal (or matralineal in birds, apparently) trait is, well, simple. A trait that appears in only one sex but is carried only by the other is not so simple, not in mammals or birds either.

OK, I'll take your question above as my que to present my proposal, but I'm spoilering it in case you're still thinking through your own.

Spoiler: Proposed Magic Inheritance Mechanism

Show

Magical ability is granted by a gene on the X chromasome; let's call the version with it X'. Only an XX' pair manifests the trait. When cells of a female with the XX' pair undergo meiosis, the X' ova are not viable, so she can't pass the X' on.

Now, one might be thinking that a man could be X'Y and give the X' to his daughters. But he can't, because he'd have to have got the X' from his mother, which couldn't have happened. So here's the trick. Well, the second trick; the first one was X' ova not being viable.

There exists a rare, Y linked trait; call the chromasome with the gene for it Y'. A man with the Y' chromasome produces an enzyme called magicilaze. Magicilaze, when the male's cells undergo meiosis, causes the X crhomazomes to be altered and become X'. So his daughters are XX' casters, and his sons are XY' carriers.

This scheme isn't perfect, mainly because being known as an XY' would be such a reproductive advantage the the Y' chromasome would not stay rare for long. A variety of tweeks to the above are possible to mitigate that and other flaws. But I should be getting to bed, so we can discuss those tomorrow.

[brian 333]

Spoiler: brian's response to jqavin's theory

Show

The X chromosome is where the trait for magic resides, and thus it is passed from mother to son or daughter. However, when XX, the trait self cancels, and females cannot be magic users. Even rare XXY combinations produce non-magical offspring. However, XY combinations never suppress the X side chromosome resulting in the potential for magic use.

In this way, magic is passed from mother to daughter, neither of which have magical powers, but their sons will.

[Lvl 2 Expert]

I don't think it fixes the problem, at least not by itself.

Oh sure, you'd have to assume the gene only activates in women, due to hormone levels regulated by master genes on their unique chromosome. The magic gene zits on the Z chromosome, but it only activates in a ZW individual (female), not ZZ (male). (With the exception of special cases maybe, similar to how there are several rare "sex does not match chromosomes" and intersex conditions in humans.)

(The Z and the W are used to make it clear which sex chromosomal system you're talking about.)

To draw a not quite perfect parallel: Men go bald easier, earlier and more often then women. This is due to testosterone levels. Yet several genes related to baldness reside on the X-chromosome, which every man gets from their mother. So if you want to have an estimate of how bald you will get you have to look at your mother's male family members. (Or just wait, that works too.) It's like that, only with the sex chromosomes switched.

(To make it more complex, yes, X-chromosomal recessive traits are more common in men in general because they have only one copy, think color blindness. So a magic gene on the Z-chromosome that is recessive (= not dominant, if you have two different versions of this gene the recessive version will not be the one that determines what happens, the dominant one is) would already make more women than men magic users. But it would not exclude men altogether. And since magic does not offer a selective disadvantage there is no reason for the gene to have evolved as a recessive gene. So I figure a Z-chromosomal trait activated by W-chromosomal hormones is the best way to do this.)

One particularity of this proposed system is that a father has two Z-chromosomes to pass on, so if a father has a very strong magical chromosome and a very weak one he can have several daughters some of which are archmages and some of which are muggles.

At the end of the day I also think the "how does it work" is not that important for a fantasy setting, as long as you have rules for it. If you can describe what happens on a human scale you don't need genetic tricks to make it work.

[jqavins]

At the end of the day I also think the "how does it work" is not that important for a fantasy setting, as long as you have rules for it. If you can describe what happens on a human scale you don't need genetic tricks to make it work.

With any mechanism that effects only the magic trait that's true. A mechanism ought to be considered, in my opinion, only to determine if it will have other effects, and what those other effects would be. The baldness prediction is a perfect if minor example. If baldness is caused by testosterone in a WZ system, the maternal grandfather would not be the place to look. Other and more important implications are possible.

Of course, one could simply declare "It works somehow and doesn't affect anything else, and never mind how. It's magic. Yes, you're very smart, now shut up." And that's fine too.

[rferries]

With any mechanism that effects only the magic trait that's true. A mechanism ought to be considered, in my opinion, only to determine if it will have other effects, and what those other effects would be. The baldness prediction is a perfect if minor example. If baldness is caused by testosterone in a WZ system, the maternal grandfather would not be the place to look. Other and more important implications are possible.

Of course, one could simply declare "It works somehow and doesn't affect anything else, and never mind how. It's magic. Yes, you're very smart, now shut up." And that's fine too.

Very reasonable. I myself prefer to keep fantasy and science separate, so I would just say "women are sorcerers, but men determine the strength of their daughter's sorcery" with no explicit reference to genetics.

Also, Sharad9 - I notice you've made posts about pregnancy, menstrual cycles, sex-determined inheritance of magic etc. May I ask why there's such a focus on gender and reproduction in your work? Planning an X/Y post-apocalyptic world? (like the comic book)

[Max_Killjoy]

In this world, families are generally based around clan systems, with clan mothers being at its head. Exogamy is practiced among families, in which people marry into clans rather than one individual. Men are primarily chosen to marry into clans, often to secure alliances or trade deals between families. Women sometimes join other clans by being adopted into them.

Magic is exclusive to women in this world. However, only men carry the gene that allows magic to be possible. The strength of this gene determines the potential power of the magic user, although other things like training play a role. For this reason, men with the strongest genetic makeup are highly valuable, and are used to unite families or forge alliances similar to how princesses were treated in the middle ages.

How would this affect the role of men in society and culture? Would this lead to inbreeding or genetic deformities, or bottleneck populations?

This is really hard to do with conventional genetics as we understand them.

• If the trait is recessive and on the X chromosome, either sex can inherit it but only women can express it -- and both parents have to have contributed a magic-positive X chromosome.
• If the trait is on the Y chromosome, only men can inherit it.
• If the trait is on the X chromosome and dominant, then either sex can inherit it and express it.

But it has to be more complex than that to make it both only inheritable through the male line and only expressible in females.

Linking magic strictly to the male line and making it strictly expressed in makes is easy -- put the gene on the Y chromosome.

[jqavins]

Very reasonable. I myself prefer to keep fantasy and science separate, so I would just say "women are sorcerers, but men determine the strength of their daughter's sorcery" with no explicit reference to genetics.

When people bring up material science, weird orbits, and most other things I quite agree. Somehow, because the question of an inherited trait was brought up, I just got going on genetic inheritance, even though it really isn't necessary. Perhaps I shouldn't have bothered.

This is really hard to do with conventional genetics as we understand them.

You're a little late to that party.

Sharad9, if I have sidetracked your thread to its destruction, I apologize.

[FreddyNoNose]

This is really hard to do with conventional genetics as we understand them.

• If the trait is recessive and on the X chromosome, either sex can inherit it but only women can express it -- and both parents have to have contributed a magic-positive X chromosome.
• If the trait is on the Y chromosome, only men can inherit it.
• If the trait is on the X chromosome and dominant, then either sex can inherit it and express it.

But it has to be more complex than that to make it both only inheritable through the male line and only expressible in females.

Linking magic strictly to the male line and making it strictly expressed in makes is easy -- put the gene on the Y chromosome.

Codominance does exist.

[Max_Killjoy]

Codominance does exist.

How does this allow for a male-line trait that only expresses itself in females?

Genuinely curious.

[Newtonsolo313]

What if its not the persons gene but the gene of say an organelle that the father passes to the child? it does not necessarily have to be in the 23 chromosomes of the person

[rferries]

When people bring up material science, weird orbits, and most other things I quite agree. Somehow, because the question of an inherited trait was brought up, I just got going on genetic inheritance, even though it really isn't necessary. Perhaps I shouldn't have bothered.

No, not at all! The thread title explicitly mentions genes anyways, you're good. :)

[jqavins]

The thread title explicitly mentions genes anyways.

Oh, right. I forgot that detail. That must be why I thought about them.

What if its not the persons gene but the gene of say an organelle that the father passes to the child? it does not necessarily have to be in the 23 chromosomes of the person

As far as I know (which may not be far enough) mitochondria are the only organelles with their own DNA, and that comes exclusively from the mother. I expect that, if there are any others, they'd come from the mother too, because the sperm are exceptionally small cells, just carriers for the 23 paternal chromasomes really. (A "regular" cell has chromasome pairs, 23 of them in humans.) Sperm could almost be viruses. They're not, but almost . Sorta.

[Lvl 2 Expert]

Oh, right. I forgot that detail. That must be why I thought about them.


As far as I know (which may not be far enough) mitochondria are the only organelles with their own DNA, and that comes exclusively from the mother. I expect that, if there are any others, they'd come from the mother too, because the sperm are exceptionally small cells, just carriers for the 23 paternal chromasomes really. (A "regular" cell has chromasome pairs, 23 of them in humans.) Sperm could almost be viruses. They're not, but almost . Sorta.

Maybe in this universe that's not the case. The sperm cell evolved to carry maginelles because the mother often does not have them anymore. Weak maginelles can get destroyed by the hormones meant to activate them. That's why there was selection pressure to have the maginelles come from the sperm rather than the egg. It takes a bit more energy and protein to make sperm now, but that's a fine price for magic.

[jqavins]

The sperm cell evolved to carry maginelles because the mother often does not have them anymore.

That might work. How about this?

• Magical ability is gained from the maginelles.
• Men and women may both have maginelles.
  
  • Neither men nor women all have them.
• Maginelles are only activated in cells with XX nuclear chromosomes.
• Maginelles only survive meiosis when protected by a substance that is coded on the Y chromosome.
  
  • All ova are devoid of maginells.
  • All sperm from a man with them will have them.
  • Thus, a man with maginelles in his cells will always pass them to his children, so his daughters are casters and his sons are carriers.

Weak maginelles can get destroyed by the hormones meant to activate them. That's why there was selection pressure to have the maginelles come from the sperm rather than the egg.

That I don't get; I must be missing something. If the hormones that activate them are produced by females, then how would their origin - the ovum (always X) or sperm (X in such cases) matter? Once there's an XX embryo, it seems to me that it wouldn't matter which X the miginelles came in with. What am I missing?

The next question, of course, is how and why such a convoluted system would arise. Evolution requires a sequence of small changes, and each one along the way must be advantageous, not just the end result. But that's evolution. Alternatively, one can always just say that a god(dess) did it; yay for intelligent design.

[Lvl 2 Expert]

That I don't get;

Yeah, I think your solution focusing on the meiosis is more elegant, at least for explaining it in a game. But the idea was this: if maginelles, let's say in particular weak magic magincelles, sometimes or often get destroyed in the process of activating them (that's something that just was, the ancestral condition, the first good solution to it that evolves is probably going to win), then less and less women get maginelles. So there is selective pressure to do something about it. If there are then males that by accident leave maginelles in during meiosis, the genes that do that will have/create a large evolutionary advantage, because more of these mens daughters, granddaughters etc have magic, allowing them access to better mates, more food and larger amounts of children etc. So the genes to leave the maginelles in during male meiosis gets spread.

But as I said, this is probably a bit too complex for a game, "women destroy all maginelles during meiosis" works. There is probably a biological reason for why that happens, but "you can figure that out on your own time".

[jqavins]

Mei solutions involve meiosis because it was the first thing I thought of that works.

• Father to son inheritance has to occur through the Y chromosome.
• Female only traits have to occur through the X chromosome.
• How the heck can we make this work?

And the first answer I came up with is that the father makes the X' rather than inheriting it, and that pointed to meiosis as the key meioment to work with.

[MrFoxwind]

Why not just tackle this from the other angle?

Something in the Y chromosome makes it so that men's ability to use magic is suppressed?

[jqavins]

Why not just tackle this from the other angle?

Something in the Y chromosome makes it so that men's ability to use magic is suppressed?

Because that doesn't answer the question posed by the OP in this thread. In another, s/he stated that only women can be casters, and you're solution above certainly achieves that. But this time, s/he wants the ability of some women to be casters to be inherited from their paternal lines, whereas with the Y inhibitor the caster trait would be present in all women.

[Max_Killjoy]

Why not just tackle this from the other angle?

Something in the Y chromosome makes it so that men's ability to use magic is suppressed?

Because that doesn't answer the question posed by the OP in this thread. In another, s/he stated that only women can be casters, and you're solution above certainly achieves that. But this time, s/he wants the ability of some women to be casters to be inherited from their paternal lines, whereas with the Y inhibitor the caster trait would be present in all women.

You beat me to it. I was going to point out that this doesn't restrict magic-ability inheritance to the paternal line.


E: and I see no issue with discussing genetics in this thread... the word "gene" is right there in the thread title.