Discussion of fictional eugenics program in the SF Dune-verse and how it contradicts contemporary known human genetics but suggests heavy agricultural science and Mendelian inspiration to Frank Herbert's worldview.
created: 5 May 2018; modified: 07 Mar 2019; status: finished; confidence: highly likely; importance: 3
Frank Herbert’s SF Dune series features as a central mechanic a multi-millennium human eugenics breeding program by the Bene Gesserit, which produces the main character, Paul Atreides, with precognitive powers. The breeding program is described as oddly slow and ineffective and requiring roles for incest and inbreeding at some points, which contradict most proposed human eugenics methods. I describe the two main historical paradigms of complex trait genetics, the Fisherian infinitesimal model and the Mendelian monogenic model, the former of which is heavily used in human behavioral genetics and the latter of which is heavily used in agricultural breeding for novel traits, and argue that Herbert (incorrectly but understandably) believed the latter applied to most human traits, perhaps related to his longstanding autodidactic interest in plants & insects & farming, and this unstated but implicit intellectual background shaped Dune and resolves the anomalies.
One of the odder things in the 1965 SF novel Dune, among its many exuberant ideas, is the role of genetics. Genes are constantly being invoked as a central theme, cause, and goal, molding and being molded by all main characters, but to a reader familiar with human genetics, especially modern molecular genetics, or eugenics, the role of genes makes no sense.
This is odd because Frank Herbert (1920-1986), while definitely a soft SF author who will never be mistaken for Greg Egan, was nevertheless a widely-read autodidact and great enthusiast for science and technology, turning his farm home into a demonstration project for fuel efficiency & home automation among other things, and writing a home computer manual (Without Me You’re Nothing: The Essential Guide to Home Computers, 1980). Dune famously began in a magazine article on ecological research in Oregon on dune reclamation, and Herbert did extensive background research to develop the world - eg he says “I did a year at the Library of Congress. I did about six years on the whole book (Dune). I leaned on Muslim and Arab history very heavily. I did an extensive study of Arab history. I also used the Library of the British Museum. I’ve lived in the desert. I was doing other things during those six years. Don’t get the idea that was all I did. But I did the research over a six-year period (from 1959 to 1965).”, which includes obscure historical episodes like the Caucasus resistance to Russian imperialism. The Bene Gesserit philosophy draws on General Semantics, the Mentats are based on idiot savants, the stillsuits are high-tech Bedouin robes, the ornithopters are old ideas for powered flight, the melange spice bears many resemblances to psychedelics like LSD, the ancestral memory recalls Jung’s speculations about a collective unconscious & H. P. Blavatsky’s western occultic “Akashic Records”, “Dune Tarot” is based on Tarot, the “Butlerian Jihad” accidentally wound up having not one but two references (to Herbert’s anti-development activist friend & to Samuel Butler of Erewhon) - even the bizarre speech by Leto II in God Emperor of Dune with the comparison of war to orgasms as justification for Leto II’s all-female army had a basis (Herbert cites the obscure book The Sexual Cycle of Human Warfare, Walter 19501). Herbert’s use of genetics in Dune is also far from a one-off, as themes of selective breeding/cloning/genetic engineering show up in many of his other SF books as well, like Hellstrom’s Hive or The Green Brain or The White Plague or The Dosadi Experiment or Destination: Void or or The Eyes of Heisenberg (for discussions of them, a good source is Touponce 1988, Frank Herbert). So where does the all-pervasive role of genetics come from, even if only loosely? It certainly doesn’t come from a standard behavioral genetics textbook or from standard research findings on the genetics of intelligence (the sort of topic which one might expect to inspire a fictional eugenics breeding program for intelligence and ESP).
To summarize the genetics and breeding program as described in the Dune series: for thousands of years (indeed, “across thousands of generations”), stemming from, Herbert implies in comments2, American and the USSR ‘New Soviet Man’ origins, the Bene Gesserit sisterhood has been running a persistent highly organized breeding program focused on the sisterhood’s members and the Great Houses of the human Empire, using arranged marriages and political subterfuge as necessary to create the desired crossings in the overall pedigree, aimed at increased intelligence, motor skill, social skills & manipulation, self-discipline, and most of all, the creation of the ‘Kwisatz Haderach’, a man capable of highly powerful long-range accurate precognitive ESP of the future and also accessing the ‘ancestral memories’ (the lifelong memories of all their forebears) of both their male & female lineage without losing their sanity or being ‘possessed’ by ancestral personalities.3 Precognition is already possible to a limited extent, and the female half of the ancestral memories are available to the most elite Bene Gesserit (the ‘Reverend Mothers’), but the KH apparently would possess it in far greater degree. It is unclear to what extent these are due to the previous successes of the breeding program. All of these traits are necessary to create a humanity which reaches its ‘adulthood’ and is capable of long-term planning and survival in an open-ended universe without any certainties or hard rules, without falling into crutches like the destructive “hero myth” and making true democracy a possibility4.
The BG decline to use technological methods like AI or genetic engineering in their breeding program. Shortly before Dune, the BG believe that they are finally within a generation or two of success, and plan a final cross: Lady Jessica, daughter of Baron Harkonnen, will have a daughter with Duke Leto I Atreides, and the daughter will then be backcrossed with Baron Harkonnen’s nephew, Feyd-Rautha Harkonnen, and this rather inbred & incestuous grandson will likely be the KH. Jessica, however, has a son (Paul Atreides), who unexpectedly becomes the KH and leads a rebellion against the Harkonnen, being pitted against Feyd-Rautha & Baron Harkonnen, both of whom are killed. In response to the impending disaster, the BG “preserve the [Harkonnen] bloodline” by a last-ditch mating of a BG sister (Lady Margot Fenring) with Feyd-Rautha, and count on Lady Jessica’s second child, a daughter (Alia), to preserve the other half.
In Dune Messiah, it is revealed the Bene Gesserit have a counterpart, the Bene Tleilax, who specialize in biological and genetic engineering (especially cloning); they casually reveal that they have “dabbled in various pure essences”, including a KH of their own, to study natural extremes (“nature often produces creations as deadly as ours”) in scientific conditions but they found him uncontrollable & he committed suicide. In Children of Dune, Paul Atreides’s two fraternal twins, Ghanima and Leto II, are at the center of political intrigue in the now-headless Empire, and both of them are potential KHs, driving the BG to desperate moves to retrieve their genes somehow, with their preferred solution being a brother-sister mating5, to lock in the KH genes into an offspring despite the political scandal and absolute condemnation of their traditional Fremen supporters, and the risk of recessive genes complicating it. They reject that option, and Leto II instead merges himself with the sandworms to become a nigh-immortal worm-human hybrid, Alia ultimately is driven insane and commits suicide, and the BG breeding program is taken over by the transformed God-Emperor Leto II. In God Emperor of Dune, Leto II takes over the BG breeding program6 for additional millennia as part of his “Golden Path” grand plan to ensure the permanent survival of the human race against the possibility of prescient machines/artificial intelligences being developed & turning against humanity; the Golden Path breeding program continues until the birth of a very distant Atreides descendant, Siona, who is invisible to prescience (a biological version of “no-ships”/“no-globes”, so perhaps one should dub Siona as having a ‘no-gene’). By this point the breeding program has successfully developed humans to the extent that the last ghola of Duncan Idaho, famed martial artist, can be defeated by even an old man;7 and by the end of the series, being a Mentat, an achievement of only the most intelligent & well-trained in Dune and something remarkable in Paul Atreides, has become commonplace (and the final mysterious enemy scoffs at Mentats - “Dime a dozen, they are.”) Siona’s actions precipitate the death of Leto II, the collapse of the human Empire, and the exodus of countless billions of humans in a diaspora across the multiverse where they will adapt and evolve to local conditions and change in unpredictable ways with the development of brand new genes. (“Think of the uncounted genes out there! Think of the potential talents floating free in universes where they might be lost forever!”)
The remaining 2 books (Heretics of Dune, Chapterhouse: Dune) deal with genetics mostly in the form of “ghola” clones, only somewhat touching on the ‘uncounted genes’ manifested in new kinds of human capabilities like the “futars” & “Honored Matres”; the final book, Chapterhouse: Dune, ends with the protagonists escaping from a mysterious enemy (who appears in the guise of kindly old ‘farmers’ on a farm discussing how to best breed their crops) along with the last Bene Tleilax who is carrying an archive of cells taken from all the major characters of the series. It is implied that they will all be cloned as gholas, with their multifarious talents preserved intact, to be used in the continued development of humanity towards the goal of adulthood.
(The Brian Herbert/Kevin J. Anderson novels apparently go into considerable detail about the origins of the BG and goals, based on the ever-expanding secret material Frank Herbert left behind, but as there is no credible third-party evidence that they are drawing on authentic material, and their novels are too lousy to read, I will ignore them here although it’s possible at least their sequels to Chapterhouse: Dune, Hunters of Dune/Sandworms of Dune, are based on some degree of authentic material which could be reverse-engineered with sufficiently careful reading.8 It would also be worth remarking on Destination: Void’s use of clones, but I don’t recall it sufficiently well, and I haven’t read The Dune Encyclopedia yet.)
To quickly summarize some relevant human & animal genetics: the behavioral genetics paradigm traces back to the British “biometric” school of genetics which began with Charles Darwin & Francis Galton discussing kinds of “blending inheritance” for the very gradual process of evolution, leading to subtle changes compounding for eons, which Darwin set out in Origin of Species; Galton’s investigations ultimately led to the central role of the normal distribution and central limit theorem and linear models and regression to the mean in mathematically modeling the inheritance of continuous traits like height, which eventually was perfected by R.A. Fisher’s infinitesimal model, where the continuity of traits like height (as opposed to simple discrete Mendelian traits which shift between different phenotypes under the influence of one or a few genes) is due to the trait being caused by the simple additive sum of the average effect from thousands or tens of thousands of genetic variants. This could even account for the countless binary or discrete traits which clearly had genetic influence and ran in families but failed to follow any kind of Mendelian pattern whatsoever, such as alcoholism or schizophrenia, by the liability threshold model where a threshold is defined and the phenotype manifests if the sum of all genetics variants & environmental influences (a normally-distributed variable) passes a certain critical total. This paradigm matches data from twin studies, adoption studies, pedigree and family studies, and has enjoyed immense success in recent decades with the advent of genome sequencing. (And we could also use it to explain other fictional genetic scenarios, like muggles/squibs/wizards in Harry Potter9 or the 3 pony races in My Little Pony: Friendship Is Magic.10) Intelligence/IQ in particular fits this paradigm well and the consensus is that it is highly polygenic, additive, much of the relevant genetic variants are common ones, and while rare variants & de novo mutations are usually responsible for cases of severe retardation, most below-average intelligence is simply the lower end of a continuum, and there are few or no rare variants which cause extremely high intelligence or which offer a large boost in intelligence.
Given this, the breeding program in Dune makes no sense. (For a good review of quantitative genetics animal breeding methods, see “One Hundred Years of Statistical Developments in Animal Breeding”, Gianola & Rosa 2015; for what Frank Herbert would’ve had access to at the time, see the dean of American animal breeding, Jay Laurence Lush’s enormously influential textbook, Animal Breeding Plans.)
A continuous polygenic trait responds quickly to selection, and in discussing eugenics, even the most pessimistic estimates of how many generations it might take to drastically increase average human intelligence or almost entirely eliminate a nasty recessive by R.A. Fisher might be 20 generations, certainly not “thousands of generations”; this would hold true of other traits one might select for, and selecting for many traits simultaneously would increase the number of generations relatively modestly. Since there are few or no rare variants fostering extremely high intelligence or other desirable traits, all of the necessary variants exist already in the human gene pool and merely need to be increased or decreased in frequency, which can be done rapidly without waiting centuries (or tens of millennia) for “hopeful mutants”. Due to the CLT, for a highly polygenic additive trait, the starting population mean may be extremely distant from the end result of a selective breeding program (no chihuahua will ever have a puppy as big as the average Saint Bernard), so it would be incorrect for the Bene Tleilax to claim that the baseline human population could occasionally throw up extremes anywhere as extreme as their ultimate ‘essences’.
If anyone did such a program, it would be self-defeating to restrict the program to a few aristocrats because the families would regress to the mean and would be constantly diluted by intermarriage from the general population (especially over millennia) and such a restriction risks various ills from a small effective population as it greatly increases the risk of bad luck and exaggerates the effects of genetic drift; it would be best to do it on as egalitarian a basis as possible, and if it has to be limited to a certain size, select anyone with high trait values with little regard for lineage.
Should a high genetic level be reached and maintained, it would then not be especially important to mate this person with that person, since it is only the average which matters, and a misaimed marriage simply means a slight reduction in selection efficiency; nor would there be anything particularly special about a brother-sister inbreeding, other than incurring inbreeding depression & an increased risk of birth defects/genetic diseases (which is not good but tolerable as long as it is not repeated, in some eras such a mating was quite common, and even now cousin marriage is common & preferred in many societies). Likewise, it would not be terribly important to carry the exact cells of particular noted figures to clone them rather than, say, a sibling or several more distant relatives.
So is it all just complete nonsense?
Well, there is an alternative paradigm of genetics, which may be more familiar to most readers: the Mendelian paradigm, traceable to Gregor Mendel and his peas, but taken up with great enthusiasm by Americans. In Mendelian genetics, the focus is overwhelmingly on single genetic variants with large effects, which since they come in pairs can have simple additive dose-response effects (0/1/2 copies), non-additive effects such as “dominance” (one copy is enough to cause the trait), “recessive” (two copies are required), and lead to complicated inheritance patterns where a trait may disappear but then pop up many generations later, or where several genetic variants may only have a particular effect when all of them are present simultaneously (“epistasis”). Mendelian genetics applies well to a number of rare human diseases, and a few oddball traits, but works particularly well in agricultural and scientific settings, where it can be demonstrated vividly and used to track mutations and investigate their effects, among many other things. The development of Mendelian genetics thus lead to a notoriously bitter academic dispute between the biometricians and the Mendelians, because neither side was wrong: there clearly were Mendelian traits which were busily being experimentally demonstrated in plants and flies and mice, but it was also clear that Mendelian approaches couldn’t account for traits like height. (For more background, see Provine’s The Origins of Theoretical Population Genetics, Gilham’s A Life of Sir Francis Galton, and Paul & Spencer 1995.) The feud was only partially resolved by R.A. Fisher’s famous unification demonstrating that the continuous traits could be seen as simply the sum of indefinitely many genetic variants each of which acted in a Mendelian manner. (In particular, Mendelianism was avidly adopted by American eugenicists, who proceeded to interpret traits like low intelligence or alcoholism or schizophrenia as being single Mendelian genetic variants, often recessive, rather than being part of a continuum in which sufferers merely have bad luck and somewhat lower average number of favorable variants. While under a biometrics paradigm, it would be about equally effective to try to increase intelligence by increasing the fertility of more intelligent people versus decreasing the fertility of lower intelligence, under American Mendelianism run amok, all low intelligence/mental illness/disease ‘must’ be due to recessives as proven by sloppy, biased - or perhaps even falsified - pedigree charts of arbitrarily dichotomized traits, and as increasing the fertility of high-trait people is largely futile then, in the absence of any kind of genetic testing coercive government-backed sterilization approaches then become the natural approach - especially for the strong liberal progressive tradition in America which was an advocate of government intervention to reshape society eg Prohibition or minimum wage.)
The Mendelian monogenic paradigm, with heavy emphasis on various nonlinear or interaction rather than simple additive effects, remains highly influential in scientific research. (Indeed, perhaps far more than it should. It seems to me that the disappointed hopes of rapidly finding most disease-causing genetic variants after the Human Genome Project rested on quasi-Mendelian beliefs and disregarding the evidence of high additive & polygenicity of most human traits including diseases, and were responsible for the candidate-gene debacle where almost all candidate-gene hits were shown by later GWASes to be false positives. Indeed, so opposed to the standard behavioral genetics paradigm were many researchers & commentators that they used the initial GWAS null findings, indicating that the “missing heritability” was due to polygenicity with many small effects and thus requiring sample sizes close to n>100,000, as reductio ad absurdums which disproved the entire enterprise; ultimately, of course, those sample sizes were reached and the hits have kept coming ever since.
Why is this the case? Perhaps because it suffers the dual problem of being offensively theoretically simple yet practically difficult to deal with; early Mendelians (eg Bateson) complained of the difficulties of understanding Galton, Pearson, or Fisher’s mathematics, while applying the statistics at all must have been enormously painful in an era where even mechanical calculators were not always available, and the implications are that for some things like GWASes hundreds of thousands or millions of samples were required, all in the service of a theory whose intellectual charm & subtlety are difficult to appreciate, and which seems prima facie false to anyone familiar with the intricate endlessly complex pathways and feedback loops of real biological systems. It can be easy to read small n data in Mendelian ways, assuming away anomalies as measurement error and the usual ‘crud factor’ of scientific research - a striking recent example is the 60-year mistaken belief that catnip response is a single Mendelian autosomal dominant trait based on Todd 1962’s 34 cats which turns out to be an additive polygenic liability-threshold trait when studied more rigorously with n~210. In addition, the monogenic approach is indisputably successful in describing many dramatic genetic diseases. And, of course, the eugenics implications for humans of Mendelian-style genetics are much less, in exactly the ways Herbert inadvertently illustrates. So perhaps we should not be too hard on researchers who naively expected to find a few dozen genetic variants which could account for most differences in intelligence or health, and which could be found looking under the lamp post using easy samples like n=100.)
In particular, as extended by Sewall Wright, it is heavily used in animal and plant breeding in creating new strains of plants with a specific desired trait, often crossed in from another varietal or even species. In those scenarios, where one is trying not to exaggerate existing traits but to copy an entire novel trait - resistance to a particular pesticide or insect, perhaps, or salt resistance, or a coat color - there may be more than one genetic variant at work, you may need a whole gene copied over from the other organism, perhaps several of them working in concert, acting epistatically, a “gene complex” as Wright dubbed them. Epistasis makes breeding difficult because the new set of genes might be broken up immediately by the recombination. If there are, say, 3 new genes brought over into an organism and it has some offspring with an unmodified organism, each offspring will have, say, odds of inheriting the full set of 3; so of 8 offspring, perhaps 7 will not have the desired trait because only the 8th managed to get all 3 simultaneously. Only 1 or 2 is no good. These are not good odds and complicate things (if you can only see the result when all 3 genes are inherited, how do you know whether there were 0, 1, or 2 in the ones without the trait?). As Lush puts it in his textbook:
Selection for epistatic effects is somewhat like building a sand pile on the seashore exposed to each incoming wave. It is easy to build a little pile between waves, but each wave which rolls over it tends to flatten out the pile. When building is stopped, some traces remain after the first wave and perhaps even a few after the second and third, but soon practically all traces of the pile are leveled away. If building continues between waves, the pile can be built a little higher before the second and third waves than it was built before the first wave but soon a size is approached which can just be maintained, the building between waves being just enough to repair the levelling action of the preceding wave.
To investigate or select, one must carry out time-consuming and difficult breeding of multiple generations, various crosses of related organisms, and so on, and one can eventually deduce all of the relevant parameters and introduce everything enough times.
But… what you can do is, once you have managed the cross, create a line of organisms which breeds true for the trait by extensive inbreeding or cloning, “linebreeding”. (The use of inbreeding for developing new lines is generally attributed to early English breeder Robert Bakewell11; breeders then avoided inbreeding as ‘incest’ and worried about inbreeding depression, engaging in extensive cross-breeding of varieties, which while avoiding both of those problems, drastically slows down progress and obscures heritability and inevitably muddles any sharp distinctions.) If you get say 16 offspring from that organism, and take the two sibling organisms with the trait, both of which you know have the full gene complex of 3 variants, and you mate them, then all of their offspring will express the trait because the 3 variants have been fixated within that line. (This sort of incestuous inbreeding approach would also help with purging harmful recessives: because they are so related, offspring will often have two copies of a harmful recessive and it will immediately cause ill health or death, rather than continue floating around the general population.) Or you could clone them and ensure the genes (and thus trait) is preserved that way - cloning is especially common in plants, and many famous plant varieties are propagated clonally because their characteristics would be lost if they were propagated sexually. (Apples are a famous example: wild apples exhibit tremendous variety but typically all taste bad and are useful mostly for making hard cider; the supermarket apple varieties all stem from single “chance seedling” apple trees discovered on farms to be unusually tasty, and then are propagated clonally for commercial sale. The Granny Smith Festival commemorates the legendary discovery of the popular green Granny Smith apple underneath Maria Ann Smith’s kitchen window, although it may also have been found growing in a pile of discarded French crab-apples, while Ginger Gold was accidentally discovered after a hurricane knocked down its surrounding normal apple trees; apple varieties can be discovered when individual limbs of trees mutate, creating bud sports, see Foxwhelp/Gala/Cripps Pink/Winesap. Basically, apples work in real life the way the X-Men work in fiction.) Then you can use that strain directly, or employ it in various other breeding programs while perpetuating the line indefinitely. All of this is common in, for example, plant cultivars or in the special mice & rat breeds (Green 1966) used in lab work. Or if a desired mutation suddenly pops up in an individual, perhaps encouraged by the use of mutagenesis like “atomic gardens”, the mutation will be lost if it is not bred heavily, possibly with relatives. There can be additional advantages to inbreeding selection (see chapter 23/30 of the draft Walsh & Lynch textbook on selection), especially in situations in which past generations can be re-bred, such as with saved seeds or in the case of Dune, gholas repeatedly cloned from old cells.
So - this alternate paradigm can neatly explain all of the oddities of the Dune breeding program! The reason it is so odd is because Herbert was drawing on the obsolete Mendelian interpretations which were heavy on epistasis and de novo mutations, as opposed to the more plausibly relevant biometric Fisherian paradigm of highly polygenic additive traits with selection on standing variation. Herbert was throughout his life interested in agriculture & genetics, as demonstrated by his demonstration home farm project and the repeated use of agricultural themes in his works (eg Hellstrom’s Hive, where a group of humans develops into eusocial insects, or The Green Brain, where human extermination of insects has catastrophically destabilized global agriculture & provoked evolution of intelligent insects).
It appears nonsensical if you aren’t familiar with animal/plant breeding, and stuff like brother-sister mating looks arbitrary or a weird sexual fetish, but such sibling mating is an established tactic for fixating a specific set of multiple genes which all depend on each other to work at all (epistasis) and common in breeding. Hence, the reason the program took so many thousands of years is that they were waiting for de novos to pop up and were fragilely assembling multiple gene complexes of epistatic variants. The BG had to maintain an elaborate program to hunt the hints of various recessive/epistatic patterns in their pedigrees (“We Bene Gesserit sift people to find the humans”), gradually concentrating sets of useful genes in prized aristocratic lineages, and occasional premature deaths or political errors could let slip a ball of yarn they had spent generations gradually winding. And there were no Siona no-genes floating around the gene pool for Leto II to select on, he had to wait patiently for it to pop up naturally in Siona. This is also why the Bene Tleilax could observe “essences” in the wild12 or offhandedly create their own Kwisatz Haderach: the BG & Leto II refuse to use anything but natural procreation, but the BT can edit and clone freely, which massively speeds things up. Finally, this is why unusual genetics jargon from the Mendelian tradition (like Leto II describing Duncan Idaho as “a first-generation cross”) pops up occasionally in the novels.
This is not to say that this is a correct view of human genetics, or that Frank Herbert necessarily had an explicit idea of epistasis and de novo mutations in mind while plotting out Dune, but it shows that in his wide reading (especially related to his hobby of farming), he could easily have picked up on existing research and methods, and these influences were woven into his novels.
Another fictional universe with genetic mechanisms is My Little Pony: Friendship Is Magic, where there are 3 pony races which are heritable. One outlier family which has all 3 races represented challenges simple Mendelian interpretations of MLP races. I review 4 attempts to reconcile the outlier with Mendelian mechanisms, and propose another interpretation, drawing on polygenic mechanisms, treating race as a polytomous liability threshold trait, which is flexible enough to explain all observations in-universe (at least for the first few seasons of MLP).
In MLP:FiM, there are 3 apparently separate & specialized pony races: “Earth ponies” (physically strong & naturally gifted at agriculture), the Pegasi (fliers who magically manipulate the weather), and Unicorns (magic specialists - the fourth type of pony, the all-female “Alicorns”, are extremely rare and are usually explained as being magical); they are not separate species and can interbreed, but can be considered breeds/races: almost all depicted families are homogenous & have offspring of the same race, they are clearly distinct, distantly related (eg Pinkie Pie & the Apples/Pears), typically reproduce within their own race, and tend to cluster geographically (with the noted exception of Ponyville).
All main characters’ families are, as far as shown, the same race as their daughter. The one exception is the Cake Family of bakers, where the two Earth ponies Mr. and Mrs. Cake have two children in season 2 episode 13 (“Baby Cakes”), a pair of fraternal twins, who are discordant - Pegasi and Unicorn. When queried by the confused main characters, Mr Cake appeals to a vague genetic explanation, claiming “My great-great-great-great grandfather was a unicorn, and Cup Cake’s great aunt’s second cousin twice removed was a Pegasus. That makes sense, right?”
The puzzle here is how can we explain that almost all families except the Cakes are homogenous in pony race, but it is still possible for one (or two) occasional discordant offspring?
A polytomous liability threshold model is sufficiently flexible as to explain all of these patterns by simply setting thresholds appropriately and expecting assortative mating. For example, there could be a single race trait which is polytomous with 2 thresholds,
Pegasi|Earth|Unicorn, and the thresholds are set sufficiently extreme as to ensure most families of 2-3 children (MLP families tending to the very small) are homogenous, such as at -2SD and +2SD. Then assortative mating ensures that most Pegasi families have a ‘race trait’ mean somewhere well below -2SD, Earth families have a mean ~0, Unicorn families have a mean trait >2, etc. Then, if Mr Cake is unusually close the 2SD threshold and Mrs Cake is unusually close to the Pegasus threshold, the two fraternal twins could inherit differentially from their parents and wind up being pushed across different thresholds. (Siblings/fraternal twins may both inherit 50% from each parent, but they will inherit different 50%s at random due to the randomization of meiosis, and their relatedness to each other can easily be ±5%, so in a particularly extreme case perhaps that would be enough.) Alternately, it could be determined by multiple binary liability threshold traits, one for each race, and the expressed race is simply the maximum of the 3 trait values; in which case similar logic holds for the two twins. The mane problem, you might say, with the liability threshold model is that it is, if anything, too flexible and so it’s hard to provide good evidence picking it out with just the MLP evidence. (In real world genetics, one could accumulate evidence for a liability threshold model by examining ‘risk’ in increasingly distant relatives and whether it drops off with genetic distance as it should, looking for continuous measurements reflecting an increased genetic trait value like depressed IQ or schizophrenia symptoms in relatives of schizophrenics, or using molecular genetic methods like GCTA or GWAS to see if a binary trait is highly polygenic, etc, but none of that is possible here.)
A Mendelian model is a little harder to come up with but there are at least 4 attempts. HelloNurse suggests a monogenic model with 3 alleles each causing a different race, Earth pony dominance, and epistasis or environmental randomization (ie low penetrance):
Mendelian ponies could have a single gene with 3 alleles, E/U/P, with EE, EU and EP earth, UU and PP respectively unicorn and pegasus and UP either unicorn or pegasus at random (i.e. depending on other genes). If the two parents are EU and EP they are earth but offspring of all three types is possible. An even simpler model: one gene with two alleles, earth and fancy, earth dominant, fancy ponies become unicorns or pegasi depending on rainbow intensity or other non-genetic factors.
Grim-S-Morrison gives a 2 gene model, with a dominant/recessive Earth/Unicorn effect and a dominant/recessive Pegasus/Unicorn, giving a Punnet table (reproducing in Markdown):
Grim S Morrison’s 2-gene model using Earth pony dominance; hypothetical Punnett square for Mr & Mrs. Cake EuPu (Earth parent) EuPu (Earth parent) EP Eu uP UU EP (Earth) EEPP (Earth) EEPu (Earth) EuPP (Earth) EuPu (Earth) Eu (Earth) EEPu (Earth) EEuu (Earth) EuPu (Earth) Euuu (Earth) uP (Earth) EuPP (Earth) EuPu (Earth) uuPP (Pegasus) uuPu (Pegasus) uu (Earth) EuPu (Earth) Euuu (Earth) uuPu (Pegasus) uuuu (Unicorn)
This admittedly has some problems explaining why Pegasi and Unicorns appear to be quite common in Equestria; it would require an extreme caste system to keep Pegasi & Unicorn families highly homogenous & a large fraction of the population, rather than being submerged in Earth ponies and mostly popping up in Earth pony families, which is so rare that multiple adult ponies could be quite surprised at any discordance. And of course, if two Pegasi ever have Earth pony offspring (rather than Pegasi or Unicorn) or two Unicorns are ever shown as having non-Unicorn offspring, the model would be immediately falsified.
Finally, Tad Stone & Soryu Aleksi take as a starting point that Earth ponies are much more common, and Unicorns rare; they don’t try to explain to explain Alicorns. They also go with a blocking method:
Going from here, the ponies would have two genes, a Unicorn and a Pegasus gene. Both genes have a dominant allele that blocks the development of wings or horns respectively, and a recessive one to develop the features:
- P: Pegasus blocker
- p: Pegasus
- U: Unicorn blocker
- u: Unicorn
An Earth pony is a pony where both genes contain at least one blocking allele…The possibilities then are as follows:
Tad Stone & Soryu Aleksi 2-gene model, racial types Race Possible allele combinations Earth pony PPUU, PpUU, PPUu, PpUu Pegasus ppUU, ppUu, ppuu Unicorn PPuu, Ppuu
This would make Mr and Mrs Cake’s children possible if both parents are PpUu:
Tad Stone & Soryu Aleksi 2-gene model, Punnett square PU Pu pU pu PU PPUU (Earth) PPUu (Earth) PpUU (Earth) PpUu (Earth) Pu PPUu (Earth) PPuu (Unicorn) PpUu (Earth) Ppuu (Unicorn) pU PpUU (Earth) PpUu (Earth) ppUU (Pegasus) ppUu (Pegasus) pu PpUu (Earth) Ppuu (Unicorn) ppUu (Pegasus) ppuu (Pegasus)
Of course this would mean that Mr and Mrs Cake each have a (possibly very distant) Pegasus and a Unicorn ancestor. However, in the series only a Pegasus cousin for Mrs Cake and a Unicorn for Mr Cake are named. With only these two as non-Earth pony ancestors it would not be possible following my own theory, but in all likelihood they don’t know all their ancestors. Also a pretty complicated combination of genes would be needed in that case and we can’t describe such a thing without knowing much, much more.
This explanation works nicely and violates the minimum of elements.
There are some further theories which I think are inconsistent with the evidence:
- CocoaNutCakery suggests a more complicated epistasis, explaining the non-observed combinations as being fatal/producing nonviable embryos, and explaining the Earth pony-like magic of Fluttershy (a Pegasus) as being due to additional magic resistance & explaining Alicorns similarly; this has the serious defect of requiring Unicorn & Pegasi families to have much lower fertility or severe infant mortality rates (which are not supported in canon and are rather against the spirit of the show).
- theaceofspadez’s “The Genetics of the Pony: The Nelson Theory for Pony Inheritance” founders on attempting to explain too much and making Alicorns far too frequent, and also postulating “Alicorn Earth/Pegasus/Unicorn” variants too.
- Tacticalrainboom’s environmental determination theory argues that it’s not genetic at all but environmental (eg Pegasi are caused by exposure to high altitude & weather magic), but this is quite a stretch as it can’t explain why Earth ponies colonizing new places have Earth pony offspring (eg. the entire Apple clan from many different locations throughout Equestria are all Earth ponies), what environment Manehattan & Ponyville have in common causing Earth ponies but which the capital city of Canterlot does not to cause mostly Unicorns, or why, if deviations from the local norm are due to random environmental fluctuations, both Cake twins would be discordant instead of being the same type (presumably any random environmental fluctuation affecting Mrs. Cake ought to affect the fraternal twin fetuses simultaneously & equally).
But wait - there are more possible explanations! Could Mrs. Cake have been cheating on Mr. Cake or they did a threesome, since fraternal twins don’t have to be fertilized by sperm from the same father, and this is why he had shifty eyes/was vague? Were surrogacies and/or egg/sperm donors involved, because one or both of the Cakes are infertile? Or could the twins have been affected prenatally by Discord at the beginning of season 2? Or perhaps ponies are not even diploid (so all the Mendelian explanations are fundamentally wrong), but polyploid, in which case just about any kind of inheritance is possible?
That said, reviewing the theories, I think my polygenic threshold models or Tad Stone’s two-gene model fit the best overall.
Frank Herbert, “Listening to the Left Hand”, Harper’s (December 1973):
…We tend to react together with a remarkable degree of similarity across boundaries that are real only to individual cells, but remain transparent to the species. We tend to go psychotic together.
Touch one part and all respond.
The totality can learn.
This implies a nonverbal chemistry of species-wide communication whose workings remain largely unknown. It implies that much of our collective behavior may be preplanned for us in the form of mechanisms that override consciousness. Remember that we’re looking for patterns. The wild sexuality of combat troops has been remarked by observers throughout recorded history and has usually been passed off as a kind of boys-will-be-boys variation on the male mystique. Not until this century have we begun to question that item of consensus reality (read The Sexual Cycle of Human Warfare by N.I.M. Walter). One of the themes of my own science fiction novel, Dune, is war as a collective orgasm. The idea is coming under discussion in erudite journals such as the General Systems Yearbook. …
- Something like pheromones (external hormones) interacting between members of the human species to weld groups into collective-action organs. (How does a mob unite and hold itself together?)
- Isolation cues that separate groups into identifiable substructures, a system possibly influenced by diet. (Aside from accent and mannerism, how do members of the British upper class recognize each other?)
Walter’s book, as hard to get as it is (it has never been reprinted), occasionally surfaces in odd places. For example, Samuel T. Cohen was impressed enough to spend several pages describing it in his 2006 autobiography Confessions Of The Father Of The Neutron Bomb. Cohen, incidentally, gives some of the few biographical details about Walter I’ve seen:
When I had finished Walter’s book, through the publisher I wrote a long letter to him, telling him how impressed I was and asking about his background - certain it was academic, that he was a professor of international relations, or philosophy, or anthropology at some prestigious British university. Some weeks later, I received a reply thanking me for my kind words and telling me I was literally the only one to write to him about his book. As for his background, no he wasn’t a professor. He had graduated from Sandhurst (the British West Point) and after a very long career retired as a colonel. He had been a combat infantry officer, fighting mainly to protect the Empire - in Africa, the Middle East, Asia, wherever; and finally in World War I and II. Over all these years of fighting and seeing war in the raw and countries gripped in the throes of war, this sexual theme gradually dawned upon him. He vowed that when his career ended he would write a book about it. Which he did, but was unable to get a publisher, so he dipped into his meager pension and had 500 copies printed at his own expense, most of which never sold.
Dune, of course, takes you through the creation of the superhero, Paul Atreides, who becomes the Mahdi of the Fremen. Please focus on that word creation because many of the elements which go into the making of the superhero are laid out for you in this work. You have here a kind of distillation of an aristocratic bureaucracy, one of whose unmentioned ancestors is the Soviet experiment. You are taken through a history of many power instruments which have been tried and discarded (or adapted to new forms).
It’s worth noting that the ancestral memories are probably part of the KH package and rely on prescience. The usual interpretation by readers that ancestral memories are encoded into DNA and passed on that way may be an overreading of the mentions of DNA: encoding into DNA doesn’t make any sense because it would imply, among other things, that ancestral memories work only for direct ancestors, cannot recall anyone whose lineage went extinct, cannot recall anything in an ancestor’s life after fertilization of their children, cannot recall dying (except for gholas), ought to decay or mutate over many millennia, have limited capacity, etc, and cannot explain how the Duncan Idaho ghola eventually recalls memories from all his gholas, even ones whose cells were never used in the final ghola! So the connection of DNA to ancestral memories is probably more in the role of a ‘key’ or ‘index’ where relatedness opens up access across time.↩
The general theme throughout the Dune series of humans becoming ever more capable and flexible generalists is undeniable, but the ultimate culmination in democracy is a little doubtful; Herbert was not a fan of dictatorship or monarchies, despite those being about the only forms of government depicted, and it seems to be consistent with a few passages like the discussions of the Honored Matres, but the only source for democracy as the end-game is a late recollection in January 2009 by Norman Spinrad:
SR: Do you believe Frank had intentions of a “Dune 7”? Along the same lines, what do think of the claim of Brian Herbert to have found floppy disks containing the “complete” Dune 7 outline in a safety deposit box years after Frank’s death? If there were notes, do you believe Brian and Kevin J. Anderson used them faithfully in their new “Dune” books?
NS: Maybe. Frank kept going as long as the big money kept rolling in. Knowing Frank’s political philosophy, I once asked him how he could keep writing this royalist stuff. He told me he planned to end the series with a novel that would transition to a fictional universe of democratic rule. Never wrote it, of course. And Brian and Kevin certainly didn’t from any 7 notes.
From Children of Dune:
“If … if Jessica has gone back to the Sisterhood completely …”
“That’d be very dangerous to us,” he said, completing the thought. “We carry the blood of their Kwisatz Haderach - their male Bene Gesserit.”
“They won’t abandon that search,” she said, “but they may abandon us. Our grandmother could be the instrument.”
“There’s another way,” he said.
“Yes - the two of us . . . mated. But they know what recessives might complicate that pairing.”
“It’s a gamble they must’ve discussed.”
“And with our grandmother, at that. I don’t like that way.” “Nor I.”
“Still, it’s not the first time a royal line has tried to . . .”
“It repels me,” he said, shuddering. She felt the movement, fell silent. “Power”, he said.
And in that strange alchemy of their similarities she knew where his thoughts had been. “The power of the Kwisatz Haderach must fail,” she agreed. “Used in their way,” he said…“You are not Osiris.” Ghanima reminded him. “Nor will I try to be.”
GEoD: Leto II says “The Sisterhood has never forgiven me for taking their breeding program away from them” in discussing motives the BG would have for acting against him.↩
In God Emperor of Dune, Leto II’s 118 year old majordomo, Moneo, initially disapproves of the use of original Duncan Idaho gholas, noting that “The Duncans are slower and less alert than anyone in your Guard.” Leto II points out that using Idaho “gives me access to a first-generation cross between an older human form and the current products of my breeding program. Siona is 21 generations from such a cross.” Duncan later attacks Moneo and is easily defeated:
“You just haven’t the guts to pay the price he’s asking”, Moneo said.
In one blurred motion, Idaho whipped his knife from its sheath and lunged at Moneo. As fast as he moved, Moneo moved faster - sidestepping, tripping Idaho and propelling him face-down onto the floor. Idaho scrambled forward, rolled and started to leap to his feet, then hesitated, realizing that he had actually tried to attack an Atreides. Moneo was Atreides. Shock held Idaho immobile. Moneo stood unmoving, looking down at him. There was an odd look of sadness on the majordomo’s face.
“If you’re going to kill me, Duncan, you’d best do it in the back by stealth”, Moneo said. “You might succeed that way.”
Idaho levered himself to one knee, put a foot flat on the floor, but remained there still clutching his knife. Moneo had moved so quickly and with such grace, so . . . so casually! Idaho cleared his throat. “How did you. . .”
“He has been breeding us for a long time, Duncan, strengthening many things in us. He has bred us for speed, for intelligence, for self-restraint, for sensitivity. You’re. . . you’re just an older model.”
It’s worth noting that Frank Herbert originally worked as a journalist and did not have a track record of developing things for long periods or taking extensive notes, aside from the original Dune trilogy, where he notes in an Omni essay (“Dune Genesis”) that “I conceived of a long novel, the whole trilogy as one book about the messianic convulsions that periodically overtake us.”, and in the preface to Heretics of Dune that “Parts of Dune Messiah and Children of Dune were written before Dune was completed. They fleshed out more in the writing, but the essential story remained intact.”↩
Note that Ramagopalan et al 2007 suggest HP magic is a few-gene model driven by dominance, but the evidence they give is equally or even more consistent with magic being a continuous trait (with perhaps a threshold), driven by polygenic additive variants.↩
If the extremes of nobility or sadism or KH-ness the Bene Tleilax are interested in are driven by de novo mutations or occasional freak aggregations of complexes, this will happen once in a while observing on a scale of centuries & interstellar-sized human populations, in the same way that albinism and other bizarre traits can pop up at random, either by a chance mutation or by a chance aggregation of recessives etc. Indeed, it has been noted that the current human population is large enough that any mutation in the human genome not quickly fatal can probably be observed somewhere in the current population, and the absence of any carrier of a particular mutation is a strong indicator that it would be a lethal mutation (because everyone with it died).
In contrast, if the extremes in question were continuous polygenic additive traits where the extreme was something like 10 or 20 standard deviations from the norm, waiting for an extreme to appear naturally would require waiting the age of the universe (ie never); this is because random fluctuations are vanishingly unlikely to drive any individual that far away from the mean. So, for example, it is quite common to observe dwarfism or giantism due to rare diseases or genetic disorders or mutations of large effect, but one will never observe a 10 foot man caused by just common genetic variants at their current mean frequencies.↩