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One of the basic premises of the Potterverse is that Muggles are much, much more common than wizards. This is what in part necessitates the need for the Wizarding world to hide itself away because, despite their superior powers, they would be overwhelmed by the far more massive Muggle population should conflict break out.

However, we also know that wizards and witches have been around a long time. In Prisoner of Azkaban, Hermione's letter mentions:

I bet he’s learning loads, I’m really jealous – the ancient Egyptian wizards were fascinating.

Given that in one of Ron's letters, the Pyramids were mentioned as magical locations, this means that while we don't have a definitive date of when wizardry entered the world, we can definitively say that wizards and witches have been around since at least 2500 B.C. Most likely they have been around much longer than that.

I could not find any evidence that suggests that magical people reproduce any faster or slower than a Muggle. Furthermore, being born to magical parents almost always means the child will also be magical (Squibs are considered very rare). While I don't have statistical evidence, it seems that merely having only one magical parent is enough to make it likely that the child will have magical abilities - based on Severus Snape, Seamus Finnigan, and of course, Tom Marvolo Riddle. Finally, there are of course Muggle-Borns, which while they are certainly very rare as a percentage of the Muggle population, they seem quite common enough at Hogwarts.

Finally, it's fairly easy to make the argument that Wizards are more powerful than Muggles in ancient times, given the lack of Muggle technology. In the modern era, there are arguments that Muggle weapons have exceeded Wizarding power, though there is not total consensus on this. It would be hard to argue, however, that Muggles had superior power (via technology) than Wizards prior to the 20th century.

In summary:

  • Magical people have been around for at least 4500 years, probably longer.
  • Magical people reproduce at roughly the same rate as Muggles.
  • For most of history, magical people have had superior power to Muggles.

The question:

Given these reasons, why is is it that the Wizarding population does not dominate the human population via natural selection?

In-universe answer only, please. I'm not looking for a "J.K. Rowling is bad at maths" kind of answer.

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DBPriGuy
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  • Because there are relatively few wizards and when wizards have attempted to make their presence known, it's ended with (attempted) genocide. – Valorum Oct 05 '16 at 17:10
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    @Valorum Wizards' presence appears to have been known before the institution of the International Statute of Secrecy, established in 1692.While Wizard-Muggle relations were no doubt poor in the couple centuries leading up to this time, I couldn't necessarily find evidence throughout all of wizarding history of this. – DBPriGuy Oct 05 '16 at 17:35
  • In-universe, magical people population does not even seem to be growing that much at all. Can't find the reference, but somewhere around here I think it was estimated to be in the hundreds or perhaps thousands. Low population growth rate maybe? I mean, look at Harry - the only child in the family. Voldemort... you get the picture. – void_ptr Oct 05 '16 at 18:01
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    "While I don't have statistical evidence, it seems that merely having only one magical parent is enough to make it likely that the child will have magical abilities" - Keep in mind that you have a biased sample. There could be 9 non-wizard children for every wizard child, but none of those 9 would go to Hogwarts or are likely to show up in the books. Also there's the historical/culture preference for keeping things "pureblooded" which might have been more prevalent in earlier ages. – Dan Smolinske Oct 05 '16 at 18:03
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    You already answered your own question. Why haven't Wizarding people dominated muggles via natural selection? Because they reproduce at the same rate. – J Doe Oct 05 '16 at 18:06
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    That's rather tautological though. The real question is "Why haven't magical powers given Wizarding people an evolutionary advantage over muggles?" But why should they? Nothing about the powers we've seen suggests that they would give Wizarding people a reproductive advantage, and while you acknowledge they haven't, you haven't provided any argument why they should. You should reframe your question. Why should magical power mean an evolutionary advantage? – J Doe Oct 05 '16 at 18:15
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    This is some great feedback, everyone! By "reproduce at roughly the same rate" - my meaning is that magical people have around the same physical fertility as Muggles. That is, I propose that a Wizarding couple is just as likely to conceive as a Muggle family, that there is nothing about magic that inherently causes magical people to be less... productive. – DBPriGuy Oct 05 '16 at 18:39
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    Therefore, I mean to propose that magical people are more likely pass on their genes overall because, within the purview of natural selection, they are more 'fit' - just as likely to bear children, with other powerful advantages over Muggles to boot which increases the likelihood of survival over that of a Muggle. – DBPriGuy Oct 05 '16 at 18:40
  • If Egypt had wizards, it would be reasonably to assume they were - or were close to - the Pharaohs... after all they were considered/claimed to be gods - perhaps magic explained any "miracles". My point is, is that Pharaohs (and perhaps the crust of Egypt's upper class) is known not only for having several wives, but also for incest - brothers marrying their sisters, fathers marrying their daughters... all to keep their "godly" blood "pure". So Egyptian wizards may to very little degree have "inter-breeded" with muggles - thus muggles stayed muggle (except for the rare muggle-born). – Baard Kopperud Oct 06 '16 at 05:09
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    un-natural selection: List of people burned as heretics –Wiki. – Mazura Oct 06 '16 at 08:07
  • Could be that squibs were much more common in ancient times. We don't have an especially good explanation for what causes them, but it isn't unreasonable to think that, say, malnutrition during pregnancy could be a factor. Or some similar problem. – Misha R Oct 06 '16 at 12:50
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    Even if wizards have been around for 6000+ years, thats no way near enough time for evolution to matter. – Jakob Oct 06 '16 at 14:22
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    Like @Jakob says. 6000 years is a pretty short time in the grand scheme of things. Also worth noting that humans are mostly immune to natural selection as time goes on. Some people never have children, some people die young, but the vast majority of the population lives "equal" lives. – 3C273 Oct 06 '16 at 21:29
  • @Mazura: that factor is probably irrelevant, because it is canon that very few if any wizards and witches were actually killed by Muggles. Mostly they just faked their own deaths. – Harry Johnston Oct 06 '16 at 22:08
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    @JDoe -- "Why should magical power mean an evolutionary advantage?" ... Because they have a far better chance to survive and recover from injuries and illnesses than muggles. Modern medical tech is currently extending both our lifespan and our quality of life but magical "medical tech" is effectively centuries ahead of us. – O.M.Y. Oct 08 '16 at 19:26
  • "Magic is a dominant and resilient gene." (JKR)

    So far, all answers have ignored Rowling's statement. First thing is: what does she mean by "resilient gene".

     – David Banner Oct 08 '16 at 22:00
  • I think it's also wrong to assert that magic as it is in 21th century is the same level as it was in 2500BC. Through the book we hear about spells and potions being invented and named after their creator. I think just the fact that wizards went into hiding in 15th century shows that prior to that, magic was so insignificant and useless nobody even noticed most of it... – Tomáš Zato Oct 19 '16 at 08:51
  • I don't really care about this question, but: Here, take an upvote to get you to the Great Question badge! – ThePopMachine Jan 09 '18 at 17:34
  • It seems it'd be more logical to ask: Why aren't wizards/witches extinct? (Not that I'd use the word 'extinct'). At least in Britain there are far fewer wizards/witches than Muggles... But I don't think it makes sense either that they would be; I'm just saying that the much smaller group would have a smaller gene pool for selection etc. – Pryftan May 05 '18 at 15:38
  • Why aren't brown-eyed people extinct? – Xodarap777 Jun 12 '18 at 22:52
  • Natural selection takes more than 5000 years though? – BCLC Nov 27 '18 at 03:03
  • Maybe Muggles are much better looking. They've probably always had to do a lot more physical exercise than the Wizards, for one. – Misha R Dec 13 '19 at 22:20

17 Answers17

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We don't need to argue about reproductive fitness to explain this.

Here in the real world, the fertility rate falls off as the standard of living increases. Until quite recently, the magical community has had a much higher standard of living than Muggles. (Arguably, they still do!) So we would expect their fertility rate, historically, to be similar to our modern rate.

The current British fertility rate is 1.87 births per woman. It was about 2.9 births per woman at one point in the 1960s; it was probably higher still earlier on, but let's take that as a reasonable number for Muggle fertility, and the current number as a proxy for Magical fertility. (It seems reasonable, perhaps even a little too high, based on what we know from the books.)

Suppose that on average one in every two magical people marry Muggles; that seems like a slightly high estimate to me, but let's go with it for now. That would increase the number of couples in the magical community by 50%, e.g., if the birth rate was exactly 2 the effective birth rate would be 3:

50% of Wizards marrying Muggles increases the effective fertility rate 50%

That makes the effective birth rate about 2.8, nearly but not quite keeping up with the nominal Muggle rate of 2.9.

Obviously this all depends on what numbers you choose. But it is plausible.

Addendum:

As PlasmaHH and Adam point out in the comments, fertility rate isn't really the best statistic to be using here, because it doesn't take into account the number of people dying before reaching reproductive age. However, I don't think this makes my argument implausible, just slightly more subtle: you have to take into consideration that fertility may be affected by both mortality rates and standard of living.

(In particular, I don't believe the mortality rate for children has changed enough since 1960 to explain more than a fraction of the drop in the fertility rate over the same period, so those figures are probably still good enough to establish plausibility.)

The effect of mortality rates on fertility can be expected to cancel itself out, leaving only the standard-of-living effect as relevant. It seems reasonable to suppose that the adjusted fertility rates (counting only children who survive to reproduce) might remain different enough to counteract the growth rate of the magical community due to Wizard-Muggle marriages.

References: this Google chart based on data from the World Bank.

Harry Johnston
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    This... is a brilliant explanation. Bravo! It's so counter-intuitive that a lack of scarcity would lead to a lower birth rate. I would not have thought of it. – DBPriGuy Oct 05 '16 at 21:48
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    @DBPriGuy If only Morpheus had presented this counter-argument to Agent Smith's assertion that humanity was a virus... –  Oct 05 '16 at 23:33
  • @Michael not to get off topic, but I had just rewatched that scene yesterday. Guess Smith's anger was misplaced after all. – DBPriGuy Oct 06 '16 at 04:05
  • To take my family in rural Norway - my grandfather were 12 siblings, my mother's were 6, the average in my school-class (mid 1980) was 2, and now it's probably somewhere below 2... In the beginning of 1900, Norway was very poor, and my mother was born just before WW2 ended. – Baard Kopperud Oct 06 '16 at 04:58
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    Another point - although the Harry Potter books doesn't really show this trend - is that fertility and when people (get married and) have children is somewhat linked to expected living age. To take the extreme - immortals - you wouldn't expect them to have any children at all... just very few to replenish deaths from accidents. Wizards are very long lived, so they'd probably have very few children. – Baard Kopperud Oct 06 '16 at 05:02
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    Also, given the wizarding world's substantial exhibited mastery over health-care/medicine (regrowing bones, etc), it's probably the case that the wizarding world had access to reliable magical birth control and/or abortions for a really long time. Modern muggles in the real world only got highly-reliable means of doing so rather recently. Assuming similar psychology (sex-drive, self-control, etc) between muggles and wizards, this would be an additional factor (possibly subsumed by, but possibly in addition to, the quality-of-life impact on childbearing rates). – mtraceur Oct 06 '16 at 05:16
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    While this is probably true and hard statistics will be impossible to come by, fertility rate is not the best possible measure to apply here. For the majority of human history, fertility rate had to be over five for a moderate growth of the population, due to most people not reaching adolescence. Since wizards have much more access to magical medical measures, even a fertility rate of 2.5 would make them grow, while preindustrial societies with 2.5 would vanish pretty quickly. – PlasmaHH Oct 06 '16 at 07:48
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    I would argue, that birth rate connection to "standard of living" is bit more complicated. High birth rate is, and was connected to high death rates for infants and children in general, so that there will be enough adults in community. (IE 4 births for 1 raised adult). Social status correlate with birth rates only in last couple of years. I guess, that with "magical healing", magical people would easily outgrow muggle population due to lower mortality rate. – Adam Fischer Oct 06 '16 at 12:20
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    The Weasley family does not seem to have a "much higher standard of living"

    "My father told me all the Weasleys have red hair, freckles, and more children than they can afford." —Draco Malfoy on the Weasley family

     – Lenne Oct 06 '16 at 14:38
  • While wizards could theoretically had had a better quality of life in pre-modern times they would have to be very circumspect about taking advantage of it. No use being able to heal, charm and apparate if it brings the local Inquisition to your door!

    (Edit) - Additionally, we are given no indication that wizarding powers would combat the cultural pressures towards reproduction that existed in pre-modern times i.e. lack of contraception and women having any sort of societally sanctioned rights after marriage.

     – Sean Condon Oct 06 '16 at 16:59
  • There's a video clip at the beginning of Idiocracy that you could probably repurpose for this answer. – T.E.D. Oct 06 '16 at 18:34
  • Ultimately, I think this a question that has a complex answer that can be explained partially through a myriad of factors. A lot of the answers do a great job of contributing an additional true factor. However, I believe this is the most correct answer, and therefore I am going to accept it. – DBPriGuy Oct 06 '16 at 19:38
  • @Lenne: Draco is comparing them to other wizards, not to Muggles, so that really doesn't tell us much. My impression, comparing the Weasley family to the family of a friend of mine in similar circumstances, is that standard of living (excluding healthcare) for Muggles nowadays is about the same as for wizards. But that's just a subjective impression, so I left it out as irrelevant. – Harry Johnston Oct 06 '16 at 21:29
  • @PlasmaHH: I've added a section to my answer to address mortality rate, I believe it could cancel itself out. – Harry Johnston Oct 06 '16 at 22:01
  • @SeanCondon: I don't think it would have been that hard to take advantage of magic, given the availability of Muggle-repelling charms, memory modification, and the like. Also don't forget Wendolyn the Weird, who "enjoyed being burned so much that she allowed herself to be caught no less than forty-seven times in various disguises." :-) I don't believe cultural pressure would be an issue either. Wizards don't care what Muggles think. – Harry Johnston Oct 06 '16 at 22:06
  • One thing the answers doesn't take into account, is that we are looking at competing systems. Any added fertility through crossbreeding for the wizards has to be deducted from the muggle fertility. – TheSexyMenhir Oct 07 '16 at 06:45
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    @AdamFischer No, while it seems to make sense, that's not how it works in reality. As child mortality went down, so did birth rate - and much more so. If you have a low chance of a child growing to be an adult, you need to make lots of children. If a child dying is very rare, you only make one or two, especially if you have some wealth (which would be diluted). Improved health-care has always resulted in lowered birth-rates on Earth. Population growth is almost entirely about food supply and wealth, not reproduction. – Luaan Oct 07 '16 at 08:23
  • @Luaan Yes, that is definitely true, i did not give much thought to it while writing my comment. – Adam Fischer Oct 07 '16 at 08:35
  • @TheSexyMenhir: there are at least 6000 Muggles for every wizard so the impact would be negligible. – Harry Johnston Oct 08 '16 at 11:32
  • @Harry Johnston: Good point - I'd forgotten the quote about Wendolyn's burning fetish!

    On the cultural side of things though it's not a matter of what muggles think. We don't have any evidence that wizards would have been any more 'enlightened' throughout history than non-magic users.

     – Sean Condon Oct 12 '16 at 20:47
  • @SeanCondon: there's an argument here that "enlightenment" is a more-or-less natural consequence of a higher standard of living. Also I don't see any particular reason to believe that the impact of standard of living on fertility rates depends on progressive values in the first place, I would presume that both women and men prefer to have fewer children as the standard of living goes up. (Neither argument is a slam-dunk, but then I'm only looking for plausibility here.) – Harry Johnston Oct 12 '16 at 20:55
  • (Obviously some religions could be an issue, but there's no evidence in-universe that the magical community has ever been religious.) – Harry Johnston Oct 12 '16 at 20:56
  • There you go. All gone. – Pryftan May 06 '18 at 21:30
  • They do end up living to much longer though. There isn't any information on how long magical humans are fertile, though a lower bound would be how old Molly Weasley was when she had Ginny. I would suspect it would be relatively longer too. – marcellothearcane Nov 01 '19 at 22:10
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It's very possible that a lot of "muggles" just didn't know they were wizards.

The book that admits students to Hogwarts needs concrete evidence of a child using magic before it will write them down as being accepted to Hogwarts. That book was put there (and likely created by) the founders of Hogwarts.

Since Hogwarts was founded just over 1000 years ago, and is likely one of the oldest (if not the oldest) establishments, before this the only way a wizard or witch would be taught magic was by home schooling, which is still used in most countries.

Therefore unless a child is born to a wizard family that knows they are wizards, they will not be taught magic. And with a family of one muggle/ one wizard, the parents may choose not not to ever teach their child to use magic.

There may even be many more muggle born children than are shown in the books, but because they don't show any signs of magical ability before the age of 11 they are just never selected to learn how to use it.

So given that children outside of wizarding families would only ever have been told they were wizards for the last 1000 years, there will only have been children growing up in wizarding families learning magic. This severely limits the population of actual magic using wizards until around 900AD, and even that is only in Britain.

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Mike.C.Ford
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  • This would also explain the seemingly random occurrence of wizards whose parents are both muggles. Similar to how in our world almost everyone can trace one's ancestry to some noble family considering both maternal and paternal blood lines. – MauganRa Oct 06 '16 at 21:20
  • Also, every squib can pass off as a muggle if they manage to adapt culturally. There are hints that squibs usually do have magical descendants. JKR even stated that this way the magic gene(s) already permeated the muggle gene pool. – MauganRa Oct 06 '16 at 21:47
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    And since spontaneous magic is linked to young children in stress... wow. Would most muggle borns accepted to Hogwarts be children that have abusive parents, are bullied in school and such? That's certainly an interesting take on the matter :) – Luaan Oct 07 '16 at 08:26
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    This is simply wrong: Therefore unless a child is born to a wizard family that knows they are wizards, they will not be taught magic. That would imply Hermione wouldn't have learnt magic. Same with Harry since he didn't grow up with his parents. Same with all Muggle-borns. And if they're not showing signs before 11 the reason is arguably simply this: they aren't magical! – Pryftan May 05 '18 at 15:41
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Disclaimer, I am not that familiar with Harry Potter nor a evolutionary biologist, but I would suspect that characters reproduce via sex like real humans, so a out-of-verse explanation would be a in-verse explanation.

Generally speaking, natural selection that leads to speciation only occurs in bottleneck population, or isolated population (numbering in the thousands). These population are small enough to have the trait/mutation to be present in the most of population, prior to migration or expansion.

Even if we talk about 4000 BCE there were millions of people. Far too many for a tiny population of magical beings to genetically alter a large portion of the human population. Generally speaking most humans don't live very far from where they were born, there may be cultural taboos about marrying/reproducing outside your culture. All these things curb genetic movement.

Finally does being magically actually confer a positive to genetic fitness? On the surface, being super strong and able to run really fast might seem like a genetic positive, but it might mean it takes more food to feed me, or I die at a young age which might negate the positives. Sometimes improving genetic fitness requires what might be seen as a regression. I.e., growing smaller brains due to the lack of food but you live to reproduce or cave shrimp losing eyes because there is little use for them and it cost energy to grow and maintain them.

A easily confused concept about evolution is that evolution doesn't have a purpose or end-goal. It is not trying to select for the best traits ever to make the best creature ever; it is simply selecting for the minimally best trait that helps that creature survive in its current environment.

Unless being magical leads one to being a prolific lover, and with 7+ billion people, a very prolific lover, I don't see why magical beings would take over the human population short of artificial selection. Though one specific case to note, though the affected population is still small overall and this might be considered a case of artificial selection via genocide/cultural-war.

Together, I would say unless the author decides to put on her biologist and or anthropologist hat and really fill out the lore there is not enough information to work out why exactly magical being haven't been selected given our current knowledge of how evolution works.

Why magic may not help you evolutionarily in a shallow example:

Say there are three people, one with a congenital hand deformity, a 'normal' human, and a magical human. There is a field of blue berries that they can pick to eat to fulfill their daily Caloric (kJ energy) intake. The person with the hand condition cannot pick enough to feed himself, he dies before he can reproduce; the genetic fault dies with him. The 'normal' human picks enough berries and lives to reproduce. The magical human picks the berries with a magical spell and lives to reproduce.

There is little reason why the magical ability would be selected over the 'normal' ability, in both instances both humans live to reproduce. Unless being magic specifically helps you survive and not just merely a convenience, there would be little pressure to select for being magical. This would be especially true in the modern world were pressures of food gather and surviving against apex predators are not as present.

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    As long as the answer makes sense within the universe, it can be considered "in-universe", so you're all good. On this answer. You bring up good points. What I'm looking for is: What are those specific disadvantages that wizards have that mitigate their evolutionary advantages? Your point about a few thousand years not being very long in evolutionary time is also well taken, however. – DBPriGuy Oct 05 '16 at 19:00
  • I added a example that might help explain why magical being might not have any evolutionary advantage. This is just one scenario and I am sure counter-examples could be thought up. – RomaH Oct 05 '16 at 19:25
  • It's a good example of how lack of scarcity can halt evolutionary progress. However, imagine a different scenario, one in which there are only enough berries for one person to survive. Since the magic user can use magic to summon berries to him- or her- self far faster than the Muggle can pick them up, both the Muggle with the hand deformity and the "normal" Muggle will starve and the magic user will live to have more chances to reproduce. – DBPriGuy Oct 05 '16 at 21:44
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    @DBPriGuy There's no evolutionary progress, there is evolutionary change. And "lack of scarcity" as you put it should increase diversity, which basically sets the scene up for more rapid evolutionary change too (basically similar to situation after mass extinction, when there is lack of competition). – hyde Oct 06 '16 at 04:50
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    We have no reason to suppose that magic follows the rules of muggle genetics. Maybe there is a limit on the total number of magicians, so increased reproduction will just create more squibs. – Paul Johnson Oct 06 '16 at 16:46
  • @hyde -- While it is indeed true that "progress" is in the eye of the beholder, there is such a thing as evolutionary trends. -- And once you have human-level sentience, the mere "change" is indeed often progress (by any view but nihilism), though I'll admit it is no longer Darwinian change. – user23715 Oct 07 '16 at 22:09
  • I immediately disagree with your assertion of 4000 BC and a tiny population being too small "to genetically alter a large portion of the human population." The gene for blue eyes was discovered to have originated somewhere between 4000bc ~ 8000bc from one ancestor. Through genetics we also know that this gene is recessive, meaning that, barring a mutation, you can't get blue eyed children unless both parents carry the recessive gene. And yet, it is estimated that 1 in 6 people have blue eyes. It is perfectly reasonable to assume, if wizardness is genetic, to have a big population. – n_b Jan 09 '18 at 17:32
  • @PaulJohnson Incorrect and correct; incorrect: they have the magical gene. Correct: We have evidence to the contrary. But limits? Do the Weasleys not count then? Whilst I would never say impossible your suggestion is highly implausible. This includes the way evolution works as a reason that it doesn't apply. And as the question even states: Squibs are quite rare! – Pryftan May 05 '18 at 15:45
  • @DBPriGuy Right, but consider that one of the three people, the handless guy, the muggle guy, the magician realize a food shortage is coming. They would likely fight. As the magician would have an advantage here, the theory holds still though. This is just the more realistic scenario. However, also consider the case where there is a group of people and where the magicians is a minority. The magicians would be on most, but they would also be different. There will likelt be the case some muggles starts to convince people the berries collected with magic is poisonous and magic is dangerous. – patrik May 08 '19 at 21:57
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We can only speculate of course, but it seems that having magic opens you to a new world of diseases and predators that don't affect muggles. That could be the reason why they didn't become dominant, say after the black pest.

As an example,this is the classification the Ministry proposes for magical creatures:

X: Boring

XX: Harmless / may be domesticated

XXX: Competent wizard should cope

XXXX: Dangerous / requires specialist knowledge / skilled wizard may handle

XXXXX: Known wizard killer / impossible to train or domesticate

We muggles certainly didn't need this kind of classification for a long time.

Ram
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  • Good point, though certainly not all the dangers are limited to Wizards... For example, Hagrid brings up giants as being a danger to both magical and non-magical folks, but Muggles simply chalk up the gruesome deaths of mountain climbers to a mistake or a landslide or something. – DBPriGuy Oct 05 '16 at 21:53
  • But the muggle world is somehow separated from most magical creatures (else the secrecy of the magical world would be impossible to maintain), therefore they are a real danger only to wizards. Seen from that angle, the Statute of Secrecy is pretty noble :) – MauganRa Oct 06 '16 at 21:36
  • Hmm you're saying that dragons can't kill Muggles? And that Dementors can't affect Muggles? Dragons certainly have been seen by Muggles and Dementors have caused many problems for Muggles. Giants have too. And although they might have additional diseases wizards tend to not be as at risk of things like falling etc. – Pryftan Feb 17 '19 at 23:52
  • @DBPriGuy Dragons too. And Dementors. And other creatures too. It's asinine to say that only wizards can be a victim of a magical creature. And let's not forget how Azkaban actually started which involved Muggle torture/murder - and the Dementors were the least disturbing part of it. – Pryftan Feb 17 '19 at 23:54
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A curb on the wizarding population is the tendency of Muggles to fear that which they don't understand, and to kill that which they fear. And in a primitive society "that which they don't understand" covers a pretty large amount of ground, from "everything beyond the bend in the river" to "that daft old woman whut lives in the cottage off in the woods, all by 'erself-like". And it's a short walk, thinking-wise, from "daft old woman" to "Witch!". And it's an even SHORTER walk from "in the cottage off in the woods, all by 'erself-like" to the ducking stool, to the tumbril, to "Before we set the wood alight to burn the evil out of thee, witch, wouldst thou care to repent of thy sins..?". Old Tom Riddle 'imself would pale at the thought o' ten thousand peasants carrying torches and pitchforks, a-batt'rin' down his castle door..! :-)

There's also the problem of the Zulu Equation. Although magicians have more individual firepower than muggles, a dead wizard is just as dead as a dead muggle. As the British found out in South Africa, having twice the firepower of the other guy doesn't make each of your troopers twice as powerful - it's more like sqrt(2) times as powerful because, as I said, dead is dead, and the guy who's two or three or ten or 100 times as powerful as someone else is just as dead when they're dead. And as the US Army discovered in the Phillipines, the guy armed with a spear charging down the hillside at you can sometimes soak up six rounds of incoming (see Colt M1892 revolver) and still survive long enough to plant the spear right in the middle of your chest. (Which led to the development of a sidearm (the Colt New Service revolver) with enough firepower to blow major pieces of charging spearman off).

Bob Jarvis - Слава Україні
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  • Good point - although historically societies with firearms tended to eventually dominate those without unless massive logistical difficulties or a concerted, native resistance was able to dissuade them. – Sean Condon Oct 06 '16 at 17:16
  • The "Zulu" factor is mitigated quite a bit by the superior mobility and protection advantages wizards demonstrate. The British troops at Rorke's Drift had to defend ground-based fortifications against attacking troops and still repelled 20 times their number of seasoned Zulu warriors -- wizards would be able to hover in midair, well out of range, and blast away with impunity. The results could easily be considerably more lopsided. – mwigdahl Oct 10 '16 at 13:54
  • If we want to stick with battles the Zulu won vs. the British we can consider Isandlwana (same day as Rorke's Drift IIRC), Intombe, and Hlobane. Of course the British won the war in the end - superior firepower, better supply, and better transport told in the end. I wonder, though, how they might have fared 50 or so years earlier with less-capable weapons (i.e. muskets), up against an army commanded by Shaka. ??? :-) – Bob Jarvis - Слава Україні Oct 10 '16 at 16:47
  • There are also other factors. Assume there would be an armed conflict between Britain and the Magicians and that other countries mages choose to stay in the shadow (which is the realistic scenario). The magicians may be lucky and seen as the oppressed minority for a while, but if they would do too well, people would start to consider their stands. Further, the more realistic scenario is the one we see very often in the world today. The do not get employed by muggles, they are accused for taking the muggles jobs, ... Money is a contributing factor for people to marry, so well. – patrik May 08 '19 at 22:14
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Because magical powers are not an evolutionary advantage.

What matters is fitness, the ability to survive and reproduce, not "power", whatever that means. The dinosaurs were once the most powerful creatures on Earth, but their power didn't help them to survive when the meteor came. Rather, their size and strength became a liability when in the new landscape, and it was the much smaller mammals who survived and flourished.

Nothing we've seen about magical powers, and nothing you've said suggests that they would make Wizarding people any more fit to survive and reproduce than muggles. And, as you've acknowledged, they still reproduce at the same rates.

J Doe
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    So, you're saying a 12-year-old boy being able to knock out a fifteen-foot-tall predator (Troll) isn't a reproductive advantage? Being able to regrow bones? Being able to fly? None of these would provide advantage to gathering food, evading predators, or impressing mates? – user3294068 Oct 05 '16 at 18:52
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    Magic helps surviving longer. Surviving longer means more reproduction chances. – Oriol Oct 05 '16 at 19:34
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    Being able to do magic seems like a substantial advantage when it comes to impressing women. – Valorum Oct 05 '16 at 20:18
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    @user3294068 At least in the books, being able to do magic also seems to put you in contact with the magical world - which has things like fifteen-foot-tall predators (trolls). (And Quidditch seems dangerous to me - but I've got a phobia of heights, and falling seems like a distinct possibility.) Perhaps magic's evolutionary boosts are offset by the added dangers? – Ghotir Oct 05 '16 at 20:56
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    No, @user3294068, the questioner already said that when he acknowledged that magical people still reproduce at the same rate as muggles. That alone answers the question of whether magical powers are an evolutionary advantage. They are not, because their reproduction rate is the same. End of story. The question ought to be: Why should magical powers improve reproduction rates? – J Doe Oct 05 '16 at 23:02
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    ETA: Or why don't they. – J Doe Oct 05 '16 at 23:24
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    @user3294068 - I really have to wonder what evolutionary processes might have led to trolls. Most predators are relatively-speaking highly intelligent and able to mask their presence in one way or another. Trolls in the Potterverse are stupid and stinky - NOT good attributes for a predator. How do these creatures survive? What is their natural habitat? I doubt seriously if the bathrooms in various schools of magic can support a large enough population of trolls to ensure the survival of the species. ??? – Bob Jarvis - Слава Україні Oct 06 '16 at 12:03
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    @BobJarvis sounds like you should open a new question :) – DBPriGuy Oct 06 '16 at 13:42
  • @JDoe I made a clarification as to what I meant by "they reproduce at roughly the same rate" in the comments on the question. – DBPriGuy Oct 06 '16 at 13:44
  • @Valorum - I suspect (based on observations of how muggle males will sometimes use alcohol or other intoxicants in feeble attempts to overcome the resistance of muggle females) that wizards would have an entire library of spells for "convincing" females to mate with them - perhaps the "Excute illam infante" spell or something similar. :-) – Bob Jarvis - Слава Україні Oct 06 '16 at 14:03
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    @DBPriGuy This really is the answer. You could mostly translate your question to the real world by asking why stupid people aren't extinct, or physically weak people aren't extinct, etc. The answer is because those traits don't actually have a large impact on reproductive success. A trait that makes an individual more powerful or more successful does not necessarily translate to reproductive success. In human societies, the correlation has generally been an inverse one, if anything, both historically and in modern times. – HopelessN00b Oct 06 '16 at 16:53
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This is definitely hard to explain. If the Wizarding community interbred with muggles for thousands of years, population genetics would definitely lead us to expect that most humans alive today would be magical, since everyone would have at least some magical ancestors.

I get the impression from the books that interbreeding was uncommon in the past, even though it's now common. That would make it possible for most people to still not have any magical ancestors. The rise of interbreeding means that will change in the future, and we should expect a large increase in the percentage of the population with Wizarding abilities.

The facts about heritability of Wizarding, as I understand it:

  • Most children of two Wizard parents will be magical. (And no I'm not going to write Witch-or-Wizard everywhere. Please assume Wizard is a unisex term like Muggle.)
  • Most children of Wizard + Muggle will be magical
  • One Muggle parent doesn't make Squib offspring much (or at all?) more likely than for two wizard parents. (This is the most difficult part to explain with any kind of simple Mendelian genetic model.)
  • Muggle-born witches and wizards are descended from Squibs who married Muggles; the magical ability unexpectedly resurfaces after many generations. (source).

A google search for harry potter population genetics turned up a high-school science lesson plan on heritability of genetic traits using Harry Potter characters and creatures as example, published by the U.S. National Library of Medicine. The end of the second lesson (pdf) proposes a theory of heritability of magical ability where magical ability is not expressed in Muggles because they carry at least one copy of a silencing version of a gene (allele) which regulates the activity of the allele for strength of magical ability.

Their theory explains some of the phenomena from the books, but not the low rate of Squibs / Muggles from Wizard + Muggle parents. (According to their theory, every Muggle has at least one copy of the genetically dominant silencing allele, so even in the best case, children from ss(wizard) + sS(muggle) have a 50% chance of inheriting an S (silencing gene) and being pure Muggle, with not even weak magical ability. Some Muggles would carry an SS genome and be incapable of ever producing magical offspring, so clearly this model doesn't match this aspect.

Traits caused by multiple alleles have more complex behaviour, but I suspect there might not be any purely Mendelian explanation. I think the fact that children of Wizard + Muggle are no less likely to be Squibs is the hardest thing to explain. Perhaps this is a case of unreliable narrators, since the characters saying this are fighting a war against pure-blood supremacists! (And out-of-universe, I think JKR didn't want her story to include a genetic basis for discrimination.)

Perhaps at this point, interbreeding is still a new thing, and Wizards almost always have two copies of the magical allele(s). Perhaps after some generations of mixing, Muggle + Wizard will have a significantly lower chance to produce magical offspring than Wizard + Wizard.

Or maybe it's magic. Fortunately, invoking magic to explain magic is not exactly a problem, but it means we can't just use formulae from evolutionary biology / population genetics.

The extreme heritability of Wizarding should make it spread much more easily / strongly than a normal genetic mutation. It will easily become fixed throughout a population as soon as a few Wizards are common ancestors of all living humans. (This happens after enough generations, even with limited interbreeding.)

The most recent common ancestor (MRCA) of all humans alive today may have lived as recently as a few thousand years ago. The existence of long-isolated tribes may push that number back as far as the Upper Paleolithic, but a few thousand years or even shorter is probable if we don't worry about isolated pockets and just consider the bulk of Western civilization (the setting for Harry Potter).

At some point before the time of the MRCA, there's a point where everyone in the population is either an ancestor of everyone alive today or has no living descendants.

However, if Wizards limit their interbreeding with Muggles, the populations could stay separate. Wizardlyness can't spread throughout the Muggle population because of the practice of removing Wizards from their Muggle parents and bringing them into the Wizarding world. At that point they no longer count as Muggles, and are more likely to marry (or whatever) other Wizards.

The un-expressed form (that leads to Muggle-born wizards) could spread throughout the Muggle population, but IDK what the implications of that are. IDK if it's normal that Muggle-borns can identify a specific Squib ancestor, or if some just happen from random chance (i.e. inherited from an ancient magical ancestor many tens of generations ago, i.e. magic is just circulating in the gene pool.)

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Peter Cordes
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    Good genetic analysis! Worth noting: apparantely not all Muggle-borns will make it into Hogwarts, because there has to be concrete evidence of them performing magic before the age of 11. It's addressed on another question on this site somewhere.. so what about magical folk who are not pulled into the Wizarding community? Then it would seem likely they would still be in the mating pool with Muggles and so in effect, you have Wizard + Muggle (though the 'Wizard' may not know it). This could possibly work against the population separation. – DBPriGuy Oct 08 '16 at 02:26
  • @DBPriGuy: ah yes, I think you're right. I don't think I'm going to correct this answer; there's still not a lot of definite conclusions I could draw, and it took long enough to write this version. :/ – Peter Cordes Oct 08 '16 at 02:29
  • No worries, you still make a good point and have my UV – DBPriGuy Oct 08 '16 at 12:22
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    Yes. In real life, we have examples of a new mutation spreading so far as to become very common within a population, such as lactose tolerance or blue eyes, within a few thousand years. There are also populations such as Jews that historically rarely married outside their own group, and in that case genetic spread also occurred, but more slowly. So the answer depends on how endogamous Wizards were across thousands of years. Rowling suggests that Wizards did marry within their own group until recently, which means that the gene(s) for magical ability did not spread quickly. – Invisible Trihedron Dec 15 '19 at 04:31
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According to this link

Most wizards these days are half-blood anyway. If we hadn't married Muggles we'd've died out.

Let's accept that as true. Pure blood only would die out.

Muggle Wizard is more likely to produce a Wizard. This would indeed raise the Wizard population.

If a Wizard preferentially marries a Wizard they will not drive Muggle population to extinction. Wizards do preferentially marry within.

If the Wizards systematically married Muggles then the Wizard population would rise.

In summary Muggles are not extinct because Wizards tend to marry within.

paparazzo
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    I think the best In-universe answer is a combination of this and @gotorg 's idea of some pretty serious in fighting among wizards. -- Maybe there is a tendency to psychopathy among pure blood wizards OR maybe wizards who are psychopaths are, being wizards, just really effective at wiping out other contenders. – user23715 Oct 07 '16 at 21:15
  • @user23715 That come into "Pure blood only would die out". – paparazzo Oct 07 '16 at 21:19
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    Yes, but the question is, Why would they die out? -- The Weasleys certainly rule out a lack of fecundity answer. – user23715 Oct 07 '16 at 21:21
  • @user23715 Hogwarts is a limited view as the are clearly families with children. Most of the professors are single. There were not a lot of other siblings. – paparazzo Oct 07 '16 at 21:35
  • Of necessity, the whole of the canon is a limited view. That being said, many of the main characters were sans sibs for reasons of tragedy. A "tragedy" often spelled V-o-l-d-e-m-o-r-t. -- It just stands to reason that magic would (pre-industrial revolution) make it vastly more likely to see your kids make it to reproductive adulthood (Harry Johnston's answer notwithstanding). -- Really the only In-universe explanation will need to be tied directly to wizard DNA somehow. Possibly in more ways than one (e.g. engendering psychopathy and rolling back sperm count and ??). – user23715 Oct 07 '16 at 22:00
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I would place the blame on the wizarding community itself, which appears to have frequent power struggles between light and dark wizards. During Voldemort's reign of terror alone, a significant percentage of the British community was killed off. Such frequent infighting in a population would self-limit its growth through direct killings and also creating a negative environment that would discourage family formation and child-bearing to some degree.

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gotorg
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  • I think the best In-universe answer is a combination of this and @Paparazi 's idea. -- If you don't marry your kind the likelyhood of your children being wizarding types is much much less. – user23715 Oct 07 '16 at 21:17
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Anthropological and genealogical reasoning aside, the numbers on this are actually pretty clear. There may be muggle-born wizards in the school, but from a population of many millions, any given year only has at most a few dozen.

Consider (for example) a sample size of 10000 muggles and 10 wizards. Let's say the chances of 2 wizard parents having a squib are 1:10. Let's also say the chances of 2 muggles having a wizard child are 1:10000. Even at a matched birth rate of 2.5 per couple (and dropping the previous generation), the result after 10 generations would be:

92966 Muggles Born, 9 Wizards born to Muggles, 46 Wizards born (including to muggles), 4 Squibs -- effectively multiplying the muggle population by 9.3 and the wizard population by only 4.6

Now let's tweak those ratios - 1:100 squibs and 1:1000 muggle-born. This results in: 91298 Muggles, 91 Muggle-Born, 924 Wizards, 8 Squibs

Suddenly, there are a whole lot more wizards, but even after 100 generations and tens of trillions of total people, there are 21.4 muggles for every wizard.

It would take 1:100 muggle-born (with muggle-born wizards in vast quantities) and 98 generations (as well as tens of trillions of people) before wizards actually outnumbered muggles, at 1:.999

With the actual numbers being even harsher than the initial example, the math holds up.

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I consider there are quite a number of reasons for why the world is not dominated by wizarding population(and basically why I am a muggle :-( ):

  1. Magic is not a skill that could be developed over time by training. You have to born as a wizard or a witch. And the chances of you being in the center of muggles is very high. In that scenario, even though you might realize you develop few powers, you will not know how to nurture it and grow it. Add a few more generations down the line, you might have muggle children succeeding you. Remember Trelawney saying that the art of prophecy might lose a few generations. What if the art of magic can be lost for an entire bloodline?
  2. In the ancient times, people tend to live along with the "magicians" or "priests". So if you have the talent and if they train you, you can sustain those powers and be magical. If a no is on either of them, well, live as a muggle.
  3. There could be civilizations of magical people living together in the past(Still thinking of Atlantis). That will be lot safer for the wizards and witches. But might have ended due to any of the natural calamities or diseases or any other reason that ends civilizations. In that case, the world will quickly turn into a more muggle population than wizarding.
  4. There could be millions of people who born as magical but never found their powers at all and just died without using the power at all(you can call them Just Harry's). Not all people will have a Dinky Diddydums to chase them and let them experience their accidental magic.
  5. In the medieval time, it was also became very common to burn witches and wizards. This might have reduced the populace even further.
  6. Due to the medieval times, (I hope/guess) many wizards/witches started on the pure blood cr*p. Which just means, more magical people isolating from non magical, thus reducing the half blood children.
  7. Hogwarts happened only a 1000 years back and so we can safely say that until then there is no centralized school that takes each and every magical children and train them. Instead, most wizarding families might have trained their children themselves and might not extended the same to any other muggleborns, if they ever found one.
  8. Even now, magical people are still rare. Still Hogwarts kind of gets kids in only hundreds every year whereas it is a global school. Add Durmstrang and Beauxbatons to the mix as well and you will still find that the number might go up to a thousand or a little more per year. Muggles can beat that kind of population in minutes.
thiruvenkadam
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  • It's likely different in other places in HP world, but in the UK everyone exhibiting magical powers before 11 is automatically registered in Hogwarts. Wizards which are late-blossoming or too weak will fall through that sieve, but pass on their genes to the muggles. – MauganRa Oct 06 '16 at 21:59
  • Yes. But it is highly possible that lot many people who are late blossoming might not be aware of their powers. Usually, accidental magic is the way for some one to know that they have powers and in terms of adults, there are less accidents happening. That's what I explained in point 4 :) – thiruvenkadam Nov 15 '16 at 06:07
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You don't just magically know all magic, you need talent and then have to learn it. An untrained Harry Potter without any guidance would not be significantly more likely to survive in a world where you can't just order pizza.

Discovering spells with no training without blowing yourself up is hard. Figuring out what a wand is, how to make it and having it happen to choose you is very unlikely to just happen. While magic without a wand is possible, it is much harder, especially for the untrained.

Having to hide magic from Muggles is not obvious and had to be learned the hard way. Writing books about magic (those moving images are not easy to make with just sticks and rocks) and figuring out effective ways to find and train young wizards took thousands of years, so in the early days there was just not much you could do with magic due to a lack of knowledge.

Also keep in mind that food was a major concern that took most of the population's productivity. After spending the day trying not to starve the amount of time and energy you had left to practice magic was near zero, so useful discoveries were rare.

TLDR: Just like science, magic had to be discovered in a slow and difficult process.

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I offer a much simpler reason: the same reason pandas aren't. That is: people (specifically wizards, here) don't want to see them die off. It's the human nature of helping, which leads to people volunteering in third-world countries instead of letting them die off. No reason to hurt them, and they survive well enough alone.

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For most of history, magical people have had superior power to Muggles.

This does not necessarily lead to Wizards out-breeding Muggles. On the contrary, it seems that having a better quality of life actually leads to a lower birth rate. Not by biological causes, but by choice.

So, your question is similar to asking why people in developed countries don't out-breed people in poorer countries, despite having superior technology. Actually, as it seems to be in our days, it's quite the opposite which is happening.

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    Sure, but what new information does this answer add? @HarryJohnston's answer (the accepted answer) already says as much and more. – DBPriGuy Oct 07 '16 at 21:59
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It is possible that the premises described simply do not necessarily lead to the conclusion in question.
For example, humans are considerably more powerful than most other forms of life on the planet.

This includes bacteria, molds, ants and many other types of insects, and a whole lot of other animals etc. Many of these were around long before humans, but there are newer species as well. Check out "The eight super-adaptable life-forms that rule our planet" for some examples; humans represent a small percentage of the population (and even biomass) compared to some of these. Inferior powers do not automatically lead to a wipeout, even long term.

Humans have the capacity to exterminate colonies of other species and even eradicate certain life-forms intentionally, and while we are now killing off a bunch of others, it's unintentional and many folks would strongly prefer we stop doing that. Intentional, systematic eradication in most cases simply does not provide marginal benefits greater than the marginal costs of doing so. This is true even for species we consider pests or which carry disease. Further, we don't necessarily understand all the follow-on effects that might occur following the loss of the "ecosystem services" that species currently provides. At least some things that Muggles build and do are useful to wizards, and that's an explicit disincentive to wiping them out, even before any ethical considerations come in.

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  1. Natural selection is not applicable to sentient species with society.

    Society (laws, standard of living, cost of living vs capita, religion, etc.) determines reproduction rate. Biologically 'superior' and mentally 'superior' in certain societies is not correlated and may be inversely proportional to reproduction rates. An exception to this is if you define 'survival of fittest' circularly such that those who survive are by definition more 'fit'. A circular definition would mean that for reasons perhaps not obvious, wizards are less 'fit' than humans. See 2. for such speculation.

  2. The wizarding community is not self sufficent.

    Ron in Chamber of Secrets:

    Most wizards these days are half-blood anyway. If we hadn't married Muggles we'd've died out.

    Wizards can have non-magical children (squibs). That combined with other societal factors (evil wizards, standard of living, cost of living, etc) may explain why wizards appear to be an anomaly as opposed to a norm in society.

Jason Baker
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The problem is in the question: Evolutionary advantage and natural selection are irrelevant unless there's direct competition. We don't find lizards extinct simply because they're less fit than monkeys. Nor do we find that one (color) race of humans goes extinct. Nor do we find blue eyes or brown eyes eradicated.

Neanderthals are likely extinct not because they were less adapted - in fact, from what I've read, they were generally more fit on the individual level. Their winning competitors grouped up (which in itself was the more relevant advantage) - but what's important is that they were probably murdered. By agency, not evolution. Similarly, the wizarding world would have to team up on and take out the muggle world by intention and force in order for their "power" advantage to matter or become relevant.

The other half that matters is simply geographic distances - competitive love instead of competitive war. The Mongols, for example, spread their seed very intentionally. But there's plenty of reason to believe, from the books, that the wizarding world (at least mostly) kept to itself. This propensity is far more important, even if it's only slightly less than that of muggles, than fitness. Again, if the fitness isn't a matter of direct competition, it has to be a social endeavor to spread out, which doesn't seem to fit with the wizarding culture.

So, again, evolutionary fitness and natural selection are totally irrelevant to the spread of the magical genes. Until there's a war between the two camps that seeks total annihilation, at least. (At which point, having magic may not counterbalance muggle ingenuity, cooperation, individual genius, sheer numbers, or technology.)

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