Heritability of Potterverse Magic
All right, I've been kicking this idea around long enough. Time to let everyone else tear it apart and see what comes of it!
Introduction
I’ve seen several attempts at constructing a mechanism for the heritability of magic in the Potterverse. Examples include Whitehound’s and Jodel’s. Both posit that while Squibs can sense magic more than your average Muggle, there is a relatively clear dividing line between people who can control magic and those who can’t, and the inheritance theories reflect that. Jodel describes human magic as an aberration, probably introduced quite late to the human gene pool. After thinking about it for a few years, I don’t think the dividing line is clear at all. That ought to affect our ideas about how magical ability is inherited.
Part I: General Theory
Everyone’s A Little Bit Magic
In “On the Existence of Muggles,” Terri emphasizes that if Squibs (or at least some Squibs) can manipulate charmed objects, they are using magic-just not enough to reliably control a wand. Furthermore, there are enough “weak” witches and wizards to be served by a mass-market correspondence course like Kwikspell. Fred and George claim that the Ministry ordered five hundred Shield Hats because so many Ministry employees can’t cast decent Shield Charms. Not too slow at casting them. Incapable. How much can they really do with those wands they’re qualified to carry? How much difference is there between those weak wizards and Argus Filch? No, I don’t think difference between magical and non-magical people is as clear as wizards tell themselves.
Also, both Dudley and Mrs. Figg can sense (though not see) Dementors. They may be equal in magical ability, though one is a Muggle and the other a Squib. Quasi-canonical sources note that Muggles don’t entirely lack magic: Rowling claimed that Muggles could produce some effect with wands, just not control them; that Muggles can sense (though not see) ghosts; and that the Hogwarts Quill recognizes “faint signs” of magic in children which the Book of Admittance refuses to accept. Rowling says this means Muggles don’t have magic and Squibs only have lingering magical residue from their parents, but that doesn’t make as much sense as Muggles and Squibs having some small magical ability. Consider all the Muggles with uncanny hunches, green thumbs, talents for dowsing, fortune-telling, etc. Potterverse wizards can barely accept that wand-controlling witches and wizards are such if they have Muggle parents. Muggles could be using small amounts of magic all over the place and wizards wouldn’t believe it. Some Muggles could have more magical power than some Squibs. The difference between them is cultural, not magical/physical.
Once you start thinking about cultural constructs, you might ask, why is the cutoff point between “magical” and “non-magical” set at “can/can’t control a wand” rather than “can/can’t control charmed objects” or “can/can’t see ghosts”? Why aren’t Filch and Mrs. Figg considered weak but legitimate magical practitioners and sent to separate classes or a separate school for those who can control charmed objects but not wands? With the right training, they and their Muggle-born counterparts might be able to perform very skilled, if relatively weak, magic. A well-trained Squib might even out-perform a poorly-trained weak wizard.
There’s no need to posit “magic genes” which wizards have and Muggles lack, or a minimum number of magic genes required to “activate” magical potential. All humans have “magic genes,” and they’re always active. It’s just that most of us can only channel and control such small amounts of magic that it makes little practical difference.
Magic Genes?
If the genes involved aren't magical on/off switches, what are they? Perhaps they mostly help magical energy pass through our bodies without frying us. These genes in some form are probably common to all life on Earth. Say we have a handful of genes which protect us against magical energy, keyed to not-fully-overlapping magical “frequencies.” Each gene has multiple alleles, some of which handle magic better than others; an organism with the more efficient alleles could encounter bigger surges of magic without getting fried, transformed weirdly, etc. But since this isn’t a daily occurrence for most organisms, the less-efficient alleles wouldn’t be weeded out except under certain circumstances, like an isolated population living in an area with high ambient magic.
Since the magical “frequency” each gene interacts with overlaps with the others a fair bit, the effect is cumulative: someone with a couple of alleles for low channeling capacity, a couple for moderate, and one for high might be able to channel the same amount of magic as someone whose alleles all facilitate channeling moderate amounts of magic (though perhaps with small variations in which “frequencies” they handle best).
Some species, and individuals within species, can interact with magic more actively. Some plants, for instance, depend on magic for at least parts of their life-cycles. Whomping willows must need a lot of energy for their extremely active defense strategy. Some animals, like phoenixes, also depend on magical energy. (Note that some magical plants and animals may be the results of magical modification and selective breeding by wizards, not naturally arising.) Again, forms of these genes might be common to much of life on Earth: the basic ancestral genes might merely allow organisms to reflexively “push” magic away when they encounter surges too big to channel, and these or other genes might also allow organisms to instinctively harness magic as an energy source. Again, most organisms don’t need much control over magic, so the weak-magic alleles aren’t usually weeded out of populations.
Sapient species can consciously direct the magic flowing through our nervous systems to some extent, just as we can consciously modify our breathing, moods, and other bodily processes which are otherwise instinctive. Young children have less self-control, and sometimes instinctively direct surges of magic when they’re emotional-but it isn’t fully instinctive as it is for plants and animals, so outbursts don’t happen consistently. As their brains develop, they find it easier to suppress emotional and magical outbursts and consciously direct magic.
Practical Implications
With so many different factors involved, it’s no wonder magical ability is so variable. People who can only channel tiny amounts of magic and can’t connect to most of it are aren’t strictly non-magical, only effectively so. Someone with the capacity to passively channel lots of magic without harm, but little ability to control it, also has little magical ability. Maybe they can sense ghosts strongly and occasionally see them, if there’s enough ambient magic. A person with low channeling capacity but a very strong connection to that magic might be able to see ghosts consistently, and maybe use charmed objects. Both of these people, while barely magical themselves, could have highly magical children with the right partner. Humans with both a high enough channeling capacity and a strong enough connection to that magic to control a wand consistently are the “Olympic athletes, the operatic divas, of magic,” as Terri put it. Above this arbitrary cutoff point is more variation, from those Ministry employees who probably barely passed the practical sections of their OWLs up to Tom.
This complex suite of genes and their interactions explains the variations in which types of magic wizards are best at, and by extension, which wands suit them. Genes can’t control magical talents by a simple one-to-one pairing (with rare exceptions-more about that later). There is no “charms gene” or “transfiguration gene.” Otherwise, there would be wizards who could, say, transfigure objects but not cast charms, and we don’t see that. But multiple genes handling overlapping but not identical magical “frequencies” would allow for broad overall magical ability and a lot of possible variations in which “frequencies” wizards can channel best.
If there are, say, a dozen or more genes involved, the odds are low that a witch and wizard will have the right combination of weak-magic and strong-magic alleles between them to make each a decent magic-user but allow their children to inherit so many weak-magic alleles that they can’t use wands. Especially since the wizarding community now expels Squibs and their weak-magic alleles before they reproduce, and so those alleles are probably rarer in the magical community than they were a few centuries ago.
However, because the interactions are so complex, plenty of weak-to-moderate-magic alleles could be floating in the wizarding gene pool undetected, along with new ones introduced by Muggle-borns. As long as they have mostly stronger-magic alleles, a couple of weaker-magic ones won’t lower someone’s magical ability enough to make anyone suspect that they’re carrying the potential for what wizards consider a hereditary defect. A sufficiently inbred family-say, the Blacks-might all carry several weak-magic alleles unsuspected if they also carry codominant alleles for exceptionally strong magic. They would be at higher risk of producing Squibs despite being powerful themselves. Just how high risk might be obscured if they routinely toss magical late-bloomers out windows, however.
The odds are also low that two Muggles will have perfectly complementary alleles to allow their offspring to inherit enough strong-magic-facilitating alleles to be capable of controlling a wand-especially if many weak-magic alleles are dominant over strong-magic alleles, or even if they’re incompletely dominant. Even having a full set of alleles for channeling lots of magic wouldn’t help much without enough alleles for connecting strongly to that magic, and vice-versa. For generation after generation, these strong-magic-facilitating alleles produce no wand-using wizards-though they may produce Squibs of varying power.
Then there are epigenetic factors. If Muggle family has all the right alleles to produce wand-controlling witches and wizards but an epigenetic factor has silenced critical genes, that might reduce their ability enough to make them Muggle-born Squibs. But perhaps there is something to old stories of drinking from a magical spring or being granted power by the gods: places and substances full of magic might trigger heritable epigenetic changes. If the magic-facilitating alleles are no longer silenced, then bam! Potential for magical children! An already-magical person might also get a small ability boost, or a Muggle gain enough power to become a Squib (newly able to see ghosts, perhaps). In rare cases, this might transform a former Muggle or Squib into a witch or wizard.
In addition, non-magic genes might incidentally modify the channeling or control of magic. Maybe some alleles for the genes controlling converting sugars to usable energy interfere with magic more than others, who knows. In most cases the person’s magic is already weak or strong enough that it makes little practical difference. But a wizard with very strong-magic alleles and only one copy of an allele which incidentally masks magic having children with a witch carrying that same magic-masking allele might produce a Squib.
Once again, let’s remind ourselves: magical potential isn’t the only factor in magical performance. A person with strong potential could be magically ineffective due to lack of training, a poor memory, difficulty focusing, or anxiety. Someone with less raw potential but every other advantage might perform more varied, better controlled, and more effective magic.
Why Is Strong Magic So Uncommon?
Why would low-magic alleles be so common in the human population? Because the stronger-magic ones aren’t such an unmitigated benefit that their carriers would be wildly more successful at reproducing. Someone with a very high degree of control over magic but low channeling capacity might invoke magical forces they can’t handle and get fried. Goodbye, future children. Someone with high channeling capacity but low control might have fatal magical outbursts. (Like Ariana, but due to heredity rather than trauma-induced.) Someone with the capacity for both high channeling and strong control but no training could easily do fatal harm to themselves and others-like their close relatives, also carrying strong-magic alleles. Even trained witches like Luna’s mother sometimes blow themselves up, after all. Magic is risky. A magic-worker’s neighbors might freak out about their strange, dangerous abilities and kill them. Or their own families, convinced they’ve produced a demon-child or changeling. That wouldn’t exactly lead to numerous magical offspring.
And if magic use is tied to the nervous system and brain, it might damage those areas under the wrong circumstances, and there you have Jodel’s “Dark Arts dementia.” They’re swamped by fear, can no longer suppress it or their impulses to act on it, and might experience hallucinations or delusions. This probably usually develops too late in life to affect their own reproduction, but the affected person might kill younger members of their family, or maybe no one will marry their relatives. That would destroy those relatives’ capacity to produce magical offspring.
Weaker magical ability might be more beneficial in most cases. Being able to find water or game animals or having a green thumb helps you survive better if those abilities don’t come with negative “blowing yourself up” side-effects. Such talents aren’t obviously dangerous magic, which might reduce the chance of the neighbors murdering you. In England, witches were feared and persecuted, while cunning-folk were sometimes mistrusted but not so often tried as witches. (Being accused of fraud was more likely.) They could make good livings, too. Perhaps the most successful cunning-folk were strong Squibs. During witch hunts, the strongest magic-workers-the most dangerous-were attacked while weaker ones thrived. So most of our evolutionary history favored weak-to-moderate magical ability over strong magical ability.
However, weak magical ability probably wasn’t enough of a survival advantage to spread like wildfire through the population. Other things, like cleverness, physical strength, lactose tolerance, or a good immune system, were just valuable, or more so.
Unusual circumstances might favor stronger magic. Whitehound mentions precognition being useful in dangerous occupations like fishing. Being especially physically resilient (resistant to cold and drowning, say) would also be useful. So might more active types of magic, like weather-affecting charms, warming and drying charms, repairing spells (for mending holes in your sail-or boat), and perhaps levitation spells. It would be interesting to know whether Muggle-born witches and wizards historically have been born most often in fishing villages, mining towns, and other communities dedicated to dangerous professions.
So here we have our modern situation: most people can channel and control such negligible amounts of magic that it hardly counts; a sizable minority can channel and control a little bit of magic; and a few people, now a voluntarily isolated subpopulation, can channel and control a lot. Even in the wizarding community, the percentage of the population which barely has enough power and control to use wands is larger than wizards realize. But compared to humanity as a whole, they’re wildly talented.
Part 2: Special Cases
Magical Gifts
What about the special magical gifts which people either have or not, like delivering prophecies, speaking Parseltongue, or being a Metamorphmagus? I think these are controlled by separate genes entirely, though the degree to which they are expressed depends on how much magic the carrier can channel. A person with low channeling capacity and the Seer’s gift might just get rare flashes of premonition. (Incidentally, I wonder whether the prophecy-delivering ability is distinct from other types of future-telling magic. Perhaps one person could be good at reading tea leaves but never produce a prophecy, while another sees only wet tea leaves but sometimes says oddly accurate things they don’t remember?) A weak-magic Metamorphmagus might only have overly-elastic tissues and joints, or maybe not even that much, because that must take a lot of magic.
These genes may have been introduced into the human genome by interbreeding with non-human magical species, transfer of magical virus DNA, or some other mechanism. In which case, if you have one copy of the gene, what’s in the corresponding slot on the matching chromosome? Maybe a non-coding sequence that does nothing, maybe not. It might vary between gifts. Maybe the Seer’s gift can manifest weakly with a single copy of the Seer gene, because nothing’s blocking it, but the Parselmouth gene is paired with a language-related gene that’s no longer functional but is nevertheless dominant over the Parselmouth gene, so you need two Parselmouth genes to be one.
How can humans can interbreed with magical species in the first place? I suppose we have to assume that-despite the dramatic phenotypical differences-humans, goblins, giants, house-elves, and Veela are all subspecies of Homo sapiens. How we diverged so dramatically yet recently is another question. Maybe it involved small, isolated populations under particular pressures which strongly selected for magical ability (or resistance to magic, for the giants). But an exploration of magical subspecies is probably for another essay.
Community Magic
Does this model of magical heredity have any implications for the theory that widespread belief in magic can strengthen human control of magic, as Terri proposed in “Seclusion and the Dark Arts”?
Some wizards might believe this but be mistaken. If witches and wizards used to be more common relative to the effectively non-magical population, modern witches and wizards might think that loss of popular belief in magic has made it harder to work magic, causing more of those who could be witches and wizards to be born as Squibs-when in fact many early witches and wizards were Squibs by today’s standards. It was just that unlike today, they were considered witches and wizards, albeit weak ones who didn’t go to Hogwarts or use wands. Modern wizards who try to recreate ancient rites drawing on group emotions to fuel magic may only delude themselves that the effects are more powerful. Or if the results are better, it’s thanks to the placebo effect.
But I like the theory, so let’s try a modification.
Certain substances store or interact with magic more effectively. Using the inherent magic of unicorn hair, dragon heartstring, phoenix feathers, etc. to enhance the user’s power and control seems to be the point of wands. (Offloading some of the magic-channeling onto the wand may also help prevent damage to the nervous system and brain.) Many magical plant and animal parts hold magic which can be activated or directed by a wizard rather than coming entirely from the wizard, as we see with potions.
So what about magic within other people? Suppose you have a witch with strong control over magic but low channeling capacity. Perhaps she could direct some of the magic flowing through other people in the same way she can manipulate the magic in potions ingredients. This would be a tiny amount of magic for any single Muggle, but it could add up if she tapped into a lot of them. If she has high channeling capacity but weak control, then the wills of a group of Muggles focused on the same goal might help her direct her spell.
Strong emotions might focus the magical flows into more concentrated bursts-smaller, Muggle equivalents of wizarding children’s magical outbursts-which is why certain rites rely on heightened emotions. Elizabeth Wayland Barber in The Dancing Goddess notes how many traditional rituals involve group dancing, which can induce heightened or altered states of consciousness and a sense of group bonding or oneness. This might help with both raising bursts of power and directing them toward a unified goal. A group ritual might be partly effective even if all participants are only very weakly magical, and much more effective if even one participant has moderate magical ability.
Of course, this could be risky, especially if a wizard tries to channel others’ magic through himself rather than directing it from its existing points outside himself. That might overload his channeling capacity and damage his brain and nervous system. How badly depends on what he’s doing and how often he does it. Enough wizards probably damaged themselves with these techniques to form an association between using old, Dark magic and “going bad.” The reputation would naturally extend to any magic considered Dark by whatever definition, even if a specific technique doesn’t carry the same risks. How much of magical theory does the average wizard understand, after all?
Powerful Half-Bloods?
Another theory floated around here is that half-bloods are more likely to be especially powerful than the offspring of your average witch/wizard pairing. The examples are Tom (witch/Muggle), Albus (Muggle-born witch/wizard), and Harry (Muggle-born witch/wizard). Is this plausible under my model of magical inheritance?
This, too, could be false, even if the odd wizard believes (or is afraid) it’s true. We have too few data points to be sure. It seems unlikely that half-bloods are consistently more powerful than Muggle-borns and purebloods. Maybe Dean and Seamus are both super-powerful, but also modest, or perhaps late bloomers. But maybe not. Also, Muggles and Muggle-borns are not remotely genetically uniform and haven’t spent centuries weeding out weaker-magic alleles from their families. A given Muggle or Muggle-born might carry a few moderate- and weak-magic alleles along with the strong.
But the wild card factor also means they could introduce new strong-magic alleles to the wizarding gene pool. Perhaps Tom Riddle Senior could channel a shockingly high amount of magic without harm-but almost none of it connected to his nervous system, so it passed uselessly through him. If Merope carried alleles for channeling similarly high amounts of magic but with different DNA sequences, maybe that gave Tom Junior greater potential than if he’d inherited homozygous pairs. (He must have inherited alleles for exceptional magical control from Merope too. She was frightened, not incapable.) We could posit similar scenarios for the Snapes and the Dumbledores. Lily hit the genetic lottery, based on her abilities at age nine.
So, while half-bloods are by no means guaranteed to be powerful, and might introduce new alleles for weaker magical potential into the wizarding gene pool, they and Muggle-borns also have better odds than someone born to two old wizarding families of inheriting new and exciting gene combinations which do produce exceptionally powerful magic.
Souls
None of this addresses the apparent role of wizarding souls. (Whatever they are in the Potterverse-I’ll refrain from speculating about our world.) Magic seems to work in some kind of non-physical way which interacts with matter under some circumstances, and organized, non-physical magical entities can exist independently of matter. Sometimes these are “imprints” of formerly-embodied beings, arising from the long interaction of magic and highly-conductive living hosts. Maybe in some cases, a soul (or a bit of it) can switch on a silenced gene or silence an active one somehow. Maybe the bit of Voldemort’s soul in Harry silenced the dominant gene overriding Harry’s hypothetical single Parselmouth gene. Alternatively, maybe souls can express abilities of the bodies they are or used to be attached to. Maybe Harry can’t fully control his Parseltongue ability because it’s only an echo or memory from the Voldiebit with no physical grounding in him (or anywhere, until he’s nearly fifteen).
Souls seem to be involved in one of Tom’s special abilities: possession. We don’t know how that works. Maybe it’s my hypothetical mechanism whereby a wizard can tap into the magic flowing through other people, cranked up to eleven. Maybe Tom can not only connect with other people’s magic, but can ride the connection through their nervous system into their brains. He then can overlay his own thoughts and feelings on theirs, either temporarily to “drive” the person (as Diary Tom did with Ginny) or to make a permanent change (as Diary Tom Obliviated Ginny). When a bit of Tom’s soul gets lodged in Harry Potter, it’s still tenuously connected to Tom, so Harry can ride the connection into Tom’s mind-though not control it.
Conclusion
There are other special cases I haven’t covered, like non-human magic. House-elf magic must operate in different “frequencies,” or with some other key difference, to allow them to Apparate at Hogwarts when humans can’t, for example. And I realize that my very long speculation here could be boiled down to “magical ability is complicated, which conveniently lets us handwave its heritability just about any way we like.” But I do think that the evidence-such as it is-supports the idea that magical ability can’t possibly be controlled by a single gene or even a pair of genes, and that human magical ability is a spectrum with no real cutoff point. There is no such thing as a truly non-magical person, only more and less magical ones-mostly less. And though they haven’t fully examined it and don’t want to acknowledge it, to the point where they’ll resort to violence to avoid doing so, many wizards understand this on some level.
It makes you wonder what would happen if a witch or wizard published a meticulously-researched article explaining this. Or whether someone tried, and ended up silenced for their troubles.
Introduction
I’ve seen several attempts at constructing a mechanism for the heritability of magic in the Potterverse. Examples include Whitehound’s and Jodel’s. Both posit that while Squibs can sense magic more than your average Muggle, there is a relatively clear dividing line between people who can control magic and those who can’t, and the inheritance theories reflect that. Jodel describes human magic as an aberration, probably introduced quite late to the human gene pool. After thinking about it for a few years, I don’t think the dividing line is clear at all. That ought to affect our ideas about how magical ability is inherited.
Part I: General Theory
Everyone’s A Little Bit Magic
In “On the Existence of Muggles,” Terri emphasizes that if Squibs (or at least some Squibs) can manipulate charmed objects, they are using magic-just not enough to reliably control a wand. Furthermore, there are enough “weak” witches and wizards to be served by a mass-market correspondence course like Kwikspell. Fred and George claim that the Ministry ordered five hundred Shield Hats because so many Ministry employees can’t cast decent Shield Charms. Not too slow at casting them. Incapable. How much can they really do with those wands they’re qualified to carry? How much difference is there between those weak wizards and Argus Filch? No, I don’t think difference between magical and non-magical people is as clear as wizards tell themselves.
Also, both Dudley and Mrs. Figg can sense (though not see) Dementors. They may be equal in magical ability, though one is a Muggle and the other a Squib. Quasi-canonical sources note that Muggles don’t entirely lack magic: Rowling claimed that Muggles could produce some effect with wands, just not control them; that Muggles can sense (though not see) ghosts; and that the Hogwarts Quill recognizes “faint signs” of magic in children which the Book of Admittance refuses to accept. Rowling says this means Muggles don’t have magic and Squibs only have lingering magical residue from their parents, but that doesn’t make as much sense as Muggles and Squibs having some small magical ability. Consider all the Muggles with uncanny hunches, green thumbs, talents for dowsing, fortune-telling, etc. Potterverse wizards can barely accept that wand-controlling witches and wizards are such if they have Muggle parents. Muggles could be using small amounts of magic all over the place and wizards wouldn’t believe it. Some Muggles could have more magical power than some Squibs. The difference between them is cultural, not magical/physical.
Once you start thinking about cultural constructs, you might ask, why is the cutoff point between “magical” and “non-magical” set at “can/can’t control a wand” rather than “can/can’t control charmed objects” or “can/can’t see ghosts”? Why aren’t Filch and Mrs. Figg considered weak but legitimate magical practitioners and sent to separate classes or a separate school for those who can control charmed objects but not wands? With the right training, they and their Muggle-born counterparts might be able to perform very skilled, if relatively weak, magic. A well-trained Squib might even out-perform a poorly-trained weak wizard.
There’s no need to posit “magic genes” which wizards have and Muggles lack, or a minimum number of magic genes required to “activate” magical potential. All humans have “magic genes,” and they’re always active. It’s just that most of us can only channel and control such small amounts of magic that it makes little practical difference.
Magic Genes?
If the genes involved aren't magical on/off switches, what are they? Perhaps they mostly help magical energy pass through our bodies without frying us. These genes in some form are probably common to all life on Earth. Say we have a handful of genes which protect us against magical energy, keyed to not-fully-overlapping magical “frequencies.” Each gene has multiple alleles, some of which handle magic better than others; an organism with the more efficient alleles could encounter bigger surges of magic without getting fried, transformed weirdly, etc. But since this isn’t a daily occurrence for most organisms, the less-efficient alleles wouldn’t be weeded out except under certain circumstances, like an isolated population living in an area with high ambient magic.
Since the magical “frequency” each gene interacts with overlaps with the others a fair bit, the effect is cumulative: someone with a couple of alleles for low channeling capacity, a couple for moderate, and one for high might be able to channel the same amount of magic as someone whose alleles all facilitate channeling moderate amounts of magic (though perhaps with small variations in which “frequencies” they handle best).
Some species, and individuals within species, can interact with magic more actively. Some plants, for instance, depend on magic for at least parts of their life-cycles. Whomping willows must need a lot of energy for their extremely active defense strategy. Some animals, like phoenixes, also depend on magical energy. (Note that some magical plants and animals may be the results of magical modification and selective breeding by wizards, not naturally arising.) Again, forms of these genes might be common to much of life on Earth: the basic ancestral genes might merely allow organisms to reflexively “push” magic away when they encounter surges too big to channel, and these or other genes might also allow organisms to instinctively harness magic as an energy source. Again, most organisms don’t need much control over magic, so the weak-magic alleles aren’t usually weeded out of populations.
Sapient species can consciously direct the magic flowing through our nervous systems to some extent, just as we can consciously modify our breathing, moods, and other bodily processes which are otherwise instinctive. Young children have less self-control, and sometimes instinctively direct surges of magic when they’re emotional-but it isn’t fully instinctive as it is for plants and animals, so outbursts don’t happen consistently. As their brains develop, they find it easier to suppress emotional and magical outbursts and consciously direct magic.
Practical Implications
With so many different factors involved, it’s no wonder magical ability is so variable. People who can only channel tiny amounts of magic and can’t connect to most of it are aren’t strictly non-magical, only effectively so. Someone with the capacity to passively channel lots of magic without harm, but little ability to control it, also has little magical ability. Maybe they can sense ghosts strongly and occasionally see them, if there’s enough ambient magic. A person with low channeling capacity but a very strong connection to that magic might be able to see ghosts consistently, and maybe use charmed objects. Both of these people, while barely magical themselves, could have highly magical children with the right partner. Humans with both a high enough channeling capacity and a strong enough connection to that magic to control a wand consistently are the “Olympic athletes, the operatic divas, of magic,” as Terri put it. Above this arbitrary cutoff point is more variation, from those Ministry employees who probably barely passed the practical sections of their OWLs up to Tom.
This complex suite of genes and their interactions explains the variations in which types of magic wizards are best at, and by extension, which wands suit them. Genes can’t control magical talents by a simple one-to-one pairing (with rare exceptions-more about that later). There is no “charms gene” or “transfiguration gene.” Otherwise, there would be wizards who could, say, transfigure objects but not cast charms, and we don’t see that. But multiple genes handling overlapping but not identical magical “frequencies” would allow for broad overall magical ability and a lot of possible variations in which “frequencies” wizards can channel best.
If there are, say, a dozen or more genes involved, the odds are low that a witch and wizard will have the right combination of weak-magic and strong-magic alleles between them to make each a decent magic-user but allow their children to inherit so many weak-magic alleles that they can’t use wands. Especially since the wizarding community now expels Squibs and their weak-magic alleles before they reproduce, and so those alleles are probably rarer in the magical community than they were a few centuries ago.
However, because the interactions are so complex, plenty of weak-to-moderate-magic alleles could be floating in the wizarding gene pool undetected, along with new ones introduced by Muggle-borns. As long as they have mostly stronger-magic alleles, a couple of weaker-magic ones won’t lower someone’s magical ability enough to make anyone suspect that they’re carrying the potential for what wizards consider a hereditary defect. A sufficiently inbred family-say, the Blacks-might all carry several weak-magic alleles unsuspected if they also carry codominant alleles for exceptionally strong magic. They would be at higher risk of producing Squibs despite being powerful themselves. Just how high risk might be obscured if they routinely toss magical late-bloomers out windows, however.
The odds are also low that two Muggles will have perfectly complementary alleles to allow their offspring to inherit enough strong-magic-facilitating alleles to be capable of controlling a wand-especially if many weak-magic alleles are dominant over strong-magic alleles, or even if they’re incompletely dominant. Even having a full set of alleles for channeling lots of magic wouldn’t help much without enough alleles for connecting strongly to that magic, and vice-versa. For generation after generation, these strong-magic-facilitating alleles produce no wand-using wizards-though they may produce Squibs of varying power.
Then there are epigenetic factors. If Muggle family has all the right alleles to produce wand-controlling witches and wizards but an epigenetic factor has silenced critical genes, that might reduce their ability enough to make them Muggle-born Squibs. But perhaps there is something to old stories of drinking from a magical spring or being granted power by the gods: places and substances full of magic might trigger heritable epigenetic changes. If the magic-facilitating alleles are no longer silenced, then bam! Potential for magical children! An already-magical person might also get a small ability boost, or a Muggle gain enough power to become a Squib (newly able to see ghosts, perhaps). In rare cases, this might transform a former Muggle or Squib into a witch or wizard.
In addition, non-magic genes might incidentally modify the channeling or control of magic. Maybe some alleles for the genes controlling converting sugars to usable energy interfere with magic more than others, who knows. In most cases the person’s magic is already weak or strong enough that it makes little practical difference. But a wizard with very strong-magic alleles and only one copy of an allele which incidentally masks magic having children with a witch carrying that same magic-masking allele might produce a Squib.
Once again, let’s remind ourselves: magical potential isn’t the only factor in magical performance. A person with strong potential could be magically ineffective due to lack of training, a poor memory, difficulty focusing, or anxiety. Someone with less raw potential but every other advantage might perform more varied, better controlled, and more effective magic.
Why Is Strong Magic So Uncommon?
Why would low-magic alleles be so common in the human population? Because the stronger-magic ones aren’t such an unmitigated benefit that their carriers would be wildly more successful at reproducing. Someone with a very high degree of control over magic but low channeling capacity might invoke magical forces they can’t handle and get fried. Goodbye, future children. Someone with high channeling capacity but low control might have fatal magical outbursts. (Like Ariana, but due to heredity rather than trauma-induced.) Someone with the capacity for both high channeling and strong control but no training could easily do fatal harm to themselves and others-like their close relatives, also carrying strong-magic alleles. Even trained witches like Luna’s mother sometimes blow themselves up, after all. Magic is risky. A magic-worker’s neighbors might freak out about their strange, dangerous abilities and kill them. Or their own families, convinced they’ve produced a demon-child or changeling. That wouldn’t exactly lead to numerous magical offspring.
And if magic use is tied to the nervous system and brain, it might damage those areas under the wrong circumstances, and there you have Jodel’s “Dark Arts dementia.” They’re swamped by fear, can no longer suppress it or their impulses to act on it, and might experience hallucinations or delusions. This probably usually develops too late in life to affect their own reproduction, but the affected person might kill younger members of their family, or maybe no one will marry their relatives. That would destroy those relatives’ capacity to produce magical offspring.
Weaker magical ability might be more beneficial in most cases. Being able to find water or game animals or having a green thumb helps you survive better if those abilities don’t come with negative “blowing yourself up” side-effects. Such talents aren’t obviously dangerous magic, which might reduce the chance of the neighbors murdering you. In England, witches were feared and persecuted, while cunning-folk were sometimes mistrusted but not so often tried as witches. (Being accused of fraud was more likely.) They could make good livings, too. Perhaps the most successful cunning-folk were strong Squibs. During witch hunts, the strongest magic-workers-the most dangerous-were attacked while weaker ones thrived. So most of our evolutionary history favored weak-to-moderate magical ability over strong magical ability.
However, weak magical ability probably wasn’t enough of a survival advantage to spread like wildfire through the population. Other things, like cleverness, physical strength, lactose tolerance, or a good immune system, were just valuable, or more so.
Unusual circumstances might favor stronger magic. Whitehound mentions precognition being useful in dangerous occupations like fishing. Being especially physically resilient (resistant to cold and drowning, say) would also be useful. So might more active types of magic, like weather-affecting charms, warming and drying charms, repairing spells (for mending holes in your sail-or boat), and perhaps levitation spells. It would be interesting to know whether Muggle-born witches and wizards historically have been born most often in fishing villages, mining towns, and other communities dedicated to dangerous professions.
So here we have our modern situation: most people can channel and control such negligible amounts of magic that it hardly counts; a sizable minority can channel and control a little bit of magic; and a few people, now a voluntarily isolated subpopulation, can channel and control a lot. Even in the wizarding community, the percentage of the population which barely has enough power and control to use wands is larger than wizards realize. But compared to humanity as a whole, they’re wildly talented.
Part 2: Special Cases
Magical Gifts
What about the special magical gifts which people either have or not, like delivering prophecies, speaking Parseltongue, or being a Metamorphmagus? I think these are controlled by separate genes entirely, though the degree to which they are expressed depends on how much magic the carrier can channel. A person with low channeling capacity and the Seer’s gift might just get rare flashes of premonition. (Incidentally, I wonder whether the prophecy-delivering ability is distinct from other types of future-telling magic. Perhaps one person could be good at reading tea leaves but never produce a prophecy, while another sees only wet tea leaves but sometimes says oddly accurate things they don’t remember?) A weak-magic Metamorphmagus might only have overly-elastic tissues and joints, or maybe not even that much, because that must take a lot of magic.
These genes may have been introduced into the human genome by interbreeding with non-human magical species, transfer of magical virus DNA, or some other mechanism. In which case, if you have one copy of the gene, what’s in the corresponding slot on the matching chromosome? Maybe a non-coding sequence that does nothing, maybe not. It might vary between gifts. Maybe the Seer’s gift can manifest weakly with a single copy of the Seer gene, because nothing’s blocking it, but the Parselmouth gene is paired with a language-related gene that’s no longer functional but is nevertheless dominant over the Parselmouth gene, so you need two Parselmouth genes to be one.
How can humans can interbreed with magical species in the first place? I suppose we have to assume that-despite the dramatic phenotypical differences-humans, goblins, giants, house-elves, and Veela are all subspecies of Homo sapiens. How we diverged so dramatically yet recently is another question. Maybe it involved small, isolated populations under particular pressures which strongly selected for magical ability (or resistance to magic, for the giants). But an exploration of magical subspecies is probably for another essay.
Community Magic
Does this model of magical heredity have any implications for the theory that widespread belief in magic can strengthen human control of magic, as Terri proposed in “Seclusion and the Dark Arts”?
Some wizards might believe this but be mistaken. If witches and wizards used to be more common relative to the effectively non-magical population, modern witches and wizards might think that loss of popular belief in magic has made it harder to work magic, causing more of those who could be witches and wizards to be born as Squibs-when in fact many early witches and wizards were Squibs by today’s standards. It was just that unlike today, they were considered witches and wizards, albeit weak ones who didn’t go to Hogwarts or use wands. Modern wizards who try to recreate ancient rites drawing on group emotions to fuel magic may only delude themselves that the effects are more powerful. Or if the results are better, it’s thanks to the placebo effect.
But I like the theory, so let’s try a modification.
Certain substances store or interact with magic more effectively. Using the inherent magic of unicorn hair, dragon heartstring, phoenix feathers, etc. to enhance the user’s power and control seems to be the point of wands. (Offloading some of the magic-channeling onto the wand may also help prevent damage to the nervous system and brain.) Many magical plant and animal parts hold magic which can be activated or directed by a wizard rather than coming entirely from the wizard, as we see with potions.
So what about magic within other people? Suppose you have a witch with strong control over magic but low channeling capacity. Perhaps she could direct some of the magic flowing through other people in the same way she can manipulate the magic in potions ingredients. This would be a tiny amount of magic for any single Muggle, but it could add up if she tapped into a lot of them. If she has high channeling capacity but weak control, then the wills of a group of Muggles focused on the same goal might help her direct her spell.
Strong emotions might focus the magical flows into more concentrated bursts-smaller, Muggle equivalents of wizarding children’s magical outbursts-which is why certain rites rely on heightened emotions. Elizabeth Wayland Barber in The Dancing Goddess notes how many traditional rituals involve group dancing, which can induce heightened or altered states of consciousness and a sense of group bonding or oneness. This might help with both raising bursts of power and directing them toward a unified goal. A group ritual might be partly effective even if all participants are only very weakly magical, and much more effective if even one participant has moderate magical ability.
Of course, this could be risky, especially if a wizard tries to channel others’ magic through himself rather than directing it from its existing points outside himself. That might overload his channeling capacity and damage his brain and nervous system. How badly depends on what he’s doing and how often he does it. Enough wizards probably damaged themselves with these techniques to form an association between using old, Dark magic and “going bad.” The reputation would naturally extend to any magic considered Dark by whatever definition, even if a specific technique doesn’t carry the same risks. How much of magical theory does the average wizard understand, after all?
Powerful Half-Bloods?
Another theory floated around here is that half-bloods are more likely to be especially powerful than the offspring of your average witch/wizard pairing. The examples are Tom (witch/Muggle), Albus (Muggle-born witch/wizard), and Harry (Muggle-born witch/wizard). Is this plausible under my model of magical inheritance?
This, too, could be false, even if the odd wizard believes (or is afraid) it’s true. We have too few data points to be sure. It seems unlikely that half-bloods are consistently more powerful than Muggle-borns and purebloods. Maybe Dean and Seamus are both super-powerful, but also modest, or perhaps late bloomers. But maybe not. Also, Muggles and Muggle-borns are not remotely genetically uniform and haven’t spent centuries weeding out weaker-magic alleles from their families. A given Muggle or Muggle-born might carry a few moderate- and weak-magic alleles along with the strong.
But the wild card factor also means they could introduce new strong-magic alleles to the wizarding gene pool. Perhaps Tom Riddle Senior could channel a shockingly high amount of magic without harm-but almost none of it connected to his nervous system, so it passed uselessly through him. If Merope carried alleles for channeling similarly high amounts of magic but with different DNA sequences, maybe that gave Tom Junior greater potential than if he’d inherited homozygous pairs. (He must have inherited alleles for exceptional magical control from Merope too. She was frightened, not incapable.) We could posit similar scenarios for the Snapes and the Dumbledores. Lily hit the genetic lottery, based on her abilities at age nine.
So, while half-bloods are by no means guaranteed to be powerful, and might introduce new alleles for weaker magical potential into the wizarding gene pool, they and Muggle-borns also have better odds than someone born to two old wizarding families of inheriting new and exciting gene combinations which do produce exceptionally powerful magic.
Souls
None of this addresses the apparent role of wizarding souls. (Whatever they are in the Potterverse-I’ll refrain from speculating about our world.) Magic seems to work in some kind of non-physical way which interacts with matter under some circumstances, and organized, non-physical magical entities can exist independently of matter. Sometimes these are “imprints” of formerly-embodied beings, arising from the long interaction of magic and highly-conductive living hosts. Maybe in some cases, a soul (or a bit of it) can switch on a silenced gene or silence an active one somehow. Maybe the bit of Voldemort’s soul in Harry silenced the dominant gene overriding Harry’s hypothetical single Parselmouth gene. Alternatively, maybe souls can express abilities of the bodies they are or used to be attached to. Maybe Harry can’t fully control his Parseltongue ability because it’s only an echo or memory from the Voldiebit with no physical grounding in him (or anywhere, until he’s nearly fifteen).
Souls seem to be involved in one of Tom’s special abilities: possession. We don’t know how that works. Maybe it’s my hypothetical mechanism whereby a wizard can tap into the magic flowing through other people, cranked up to eleven. Maybe Tom can not only connect with other people’s magic, but can ride the connection through their nervous system into their brains. He then can overlay his own thoughts and feelings on theirs, either temporarily to “drive” the person (as Diary Tom did with Ginny) or to make a permanent change (as Diary Tom Obliviated Ginny). When a bit of Tom’s soul gets lodged in Harry Potter, it’s still tenuously connected to Tom, so Harry can ride the connection into Tom’s mind-though not control it.
Conclusion
There are other special cases I haven’t covered, like non-human magic. House-elf magic must operate in different “frequencies,” or with some other key difference, to allow them to Apparate at Hogwarts when humans can’t, for example. And I realize that my very long speculation here could be boiled down to “magical ability is complicated, which conveniently lets us handwave its heritability just about any way we like.” But I do think that the evidence-such as it is-supports the idea that magical ability can’t possibly be controlled by a single gene or even a pair of genes, and that human magical ability is a spectrum with no real cutoff point. There is no such thing as a truly non-magical person, only more and less magical ones-mostly less. And though they haven’t fully examined it and don’t want to acknowledge it, to the point where they’ll resort to violence to avoid doing so, many wizards understand this on some level.
It makes you wonder what would happen if a witch or wizard published a meticulously-researched article explaining this. Or whether someone tried, and ended up silenced for their troubles.