History and Inbreeding

What are the earliest refs you know of that mention the disadvantages of inbreeding, in animals and/or humans?

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83 Responses to History and Inbreeding

  1. I read something somewhere about the domestication of the European rabbit followed some 50 years later by a bishop’s conference in southern France that defined who could be married and who could not due degrees of consanguinity. IIRC it was in the 4th Century A.D.

  2. अनामकः says:

    Ancient hindu dharmashAstra-s prohibit marriage within the paternal line and with those with close maternal relatives.

    • gcochran9 says:

      A number of peoples had such rules: I’m looking for a case in which someone actually wrote it down.

      • अनामकः says:

        Well, they actually “wrote it down”. dharmashAstra-s are a class of texts including exemplars like Ashvalayana gRhya sutra, Apastamba gRhya sUtra, manu smRti.

  3. NumberOneCustomer says:

  4. Saint Augustine wrote it down in the 4th Century A.D. cf http://www.newadvent.org/fathers/120115.htm

  5. Harold says:

    In The Courser’s Companion, 1834, Thomas Thacker writes,

    “On breeding in-and-in, that is, from nearness of consanguinity, I have in vain consulted various philosophical and physiological authorities for a sound theory on the subject; and in practice the advocates for its utility and inutility adduce evidence so conflicting and contradictory, in such a variety of results pro and con, as to render the subject inscrutable, to a determinate conclusion, in the mind of man. One person objects to in-breeding entirely because he finds a disadvantage from it in some few instances; another approves of it altogether because he sees some instances without any apparent disadvantage; and as they approve or disapprove of it in any one species of animals, so they do in every species alike. This, I apprehend, will be found to be the common error in judging of the utility or inutility of breeding in-and-in; and that it is more prejudicial in one species than in another, and in some no disadvantage whatever is derived from it; in others a disadvantage in one respect, and an advantage in other respects, in the same species; in others wholly prejudicial, especially in their constitutional health and strength of both mental and bodily powers, as is the case with the human species.”

    But gives no references.

  6. Aristodemus says:

    On HBO’s Rome, young Gius Octavius muses that incest is “wrong in essence, because so many deformities and abortions come of it,” or words to that effect. I got the impression he was supposed to be paraphrasing a Greek philosopher (Aristotle?). It was a TV show, of course, but one that prided itself on its research.

  7. David Chamberlin says:

    If the Westermarck effect exists https://www.mcgill.ca/sociology/files/sociology/2015_-_archives_of_sexual_behavior.pdf than it really doesn’t matter much when it was first written down. People have evolved to find others they were raised with to be sexually unattractive.

    It makes perfect sense to me that evolution would work this way, that animals, not just humans, would be programmed to seek mates from outside the group they were raised with.

  8. Garvan says:

    This may be of interest, “Regulating Incestuous Marriage in the Roman Republic – Bruce Frier”
    But I don’t recall any written accounts of the reasons incestuous marriages were regulated.

  9. Andrew Oh-Willeke says:

    The Egyptians and earliest Persians seem to have been unaware of it, at least in humans, and there seems to be no mention of it in either the Sumerian corpus or the parts of the Hebrew Bible that have strong parallels to the Sumerian corpus. https://blogs.ucl.ac.uk/researchers-in-museums/2018/08/16/consanguinity-and-incest-in-ancient-egypt-2/comment-page-1/ and https://en.wikipedia.org/wiki/Epic_of_Gilgamesh So, this would seem to give us a date sometime in the Iron Age. In the Hebrew Bible incest taboos start to appear only around the part of the Torah that is no longer parallel to Sumerian texts and roughly seems to correspond to the Iron Age in the Levant. http://www.holybooks.info/incest.html The Iron Age seems to be when awareness dawned in India as well. http://chinabuddhismencyclopedia.com/en/index.php/Incest Sporadic early Iron Age incest in China is also attested as it was also in mythology, at least among elites, apparently without an awareness of the downsides involved. http://www.authorama.com/ancient-china-simplified-39.html https://en.wikipedia.org/wiki/Chinese_marriage

    Admittedly, this isn’t quite direct evidence of awareness of inbreeding depression. But, while a incest ban doesn’t establish awareness of inbreeding depression and could have other reasons, widespread inbreeding by elites would seem to establish a lack of awareness of it. It is hard to believe, for example, that King Tut’s parents really knew what their sibling marriage was putting their son at high risk of experiencing and went ahead anyway. On the other hand, ancient Greek tragedies are replete with warnings of the harms of inbreeding and disgust about it, so they may or may not have been aware of inbreeding depression at the time these stories were conceived (apparently the early Iron Age), but it certainly can’t be ruled out and it would make sense to look for insight by then.

    On the other hand, given that farmers were breeding domestic animals since the beginning of the Holocene, that seems somewhat surprising. One place to look that I don’t have access to but is available out there somewhere were the Mitanni horse breeding and raising manuals that were assimilated into the Hittite Empire ca. the 15th or 16th century BCE, on the earliest and most comprehensive and practical texts about breeding domesticated animals.

    • shadow on the wall says:

      On the other hand, given that farmers were breeding domestic animals since the beginning of the Holocene, that seems somewhat surprising.

      In some alternate world where humans were rational species, it would be the case.

      Unfortunately, in our world, after millenia of experience with breeding animals, both practical farmers and theroretical thinkers still knew jack shit.


      Richard Dawkins (The Ancestor’s Tale, pg46) notes that:
      …It was probably more difficult [for people] to work out that it might be a good idea to keep back the best seed for planting, rather than follow the obvious course of eating the best and planting the dross (my father, as a young man fresh out of college, taught agriculture to peasant farmers in central Africa in the 1940s, and he tells me that this was one of the hardest lessons to get across).

      But surviving theoretical scientific discussions of heredity are baffling. People lurch between ‘only fathers matter’ & ‘only mothers matter’, endlessly elaborating on wildly speculative (and wildly wrong) mechanistic explanations of how exactly sperm & eggs & embryos connected and formed, and in an example of “hard cases make bad law”, the focus on ‘monsters’ and other extreme cases among humans or animals badly misguided their premature attempts to elucidate universal principles comparable to that of astronomy or physics—the examples did not ‘prove any rule’, but baffled everyone trying to come up with a rule to prove. Other societies held to theories of partible paternity.

      The belief that only fathers mattered led horse breeders astray: they failed to race mares, and then took the ludicrously expensive imported Arabian stallions and crossed them with random mares, and then took the sub-par performance of their offspring as evidence that race performance was critically dependent on the dry Arabian environment and they simply had to keep importing & crossing.

      The idea that it is possible to almost arbitrarily improve a breed’s traits, or steer a breed in a direction to the point that it would have to be considered a new and clearly distinct breed for all intents & purposes, appears to have not been in circulation. It would have been deemed absurd, worthy of parody in the Laputa of Gulliver’s Travels, to imagine that dairy cows could one day yield >8x more milk.

      • random observer says:

        Indeed. The idea that “only fathers matter” as applied to humans seems to underlie the notion that one can genocide a population by war rape.

        Which is of course exactly not what is happening.

        At the more cultural level, I could see some point in it, but even then it’s usually mothers that raise the offspring, so…

        All in all, never a pragmatic strategy.

    • Steven E. Sailer says:

      In the Book of Genesis, there is a lot of in-breeding among Abraham and his close relatives. But I don’t think the Hebrews were doing as much of that later in the Old Testament.

      • dearieme says:

        Genesis is just myth. By the time you reach The Exile there’s some real history in the OT, though how you distinguish that from the contemporary false stuff I don’t know.

        • Young says:

          Did God tell you that? Otherwise, how could you possibly know? The religious element should not derail you so much. I do not need to believe in the Angel of Mons to believe that the Battle of Mons took place. I do not need to accept that Athena [or any other god] appeared at the Battle of Salamis to accept that the battle took place. If we throw out all ancient sources because they reference the supernatural we will not have much left.

  10. dearieme says:

    “the parts of the Hebrew Bible that have strong parallels to the Sumerian corpus.”

    A lovely euphemism for “were cribbed from”: congratulations.

    “given that farmers were breeding domestic animals since the beginning of the Holocene”: do we know that they controlled which individual animals mated? Much later, in parts of medieval Western Europe, the practice of Commoners sharing the use of pasture had many disadvantages – presumably having no control over mating was one.

    • dearieme says:

      On second thoughts, maybe “no control” is too strong. But “little control” may be right. Or it may be rubbish: did Commoners control mating and if so how (for cattle, sheep, ponies, geese; sometimes pigs)?

  11. dearieme says:

    Aha: “The stallions that run with the mares are carefully selected each year, and allotted an area. At present only 15 stallions are turned out for one month (mid-May to mid-June) to control the number of foals born on the Forest each year. The areas where they are released are carefully selected by the Verderers in consultation with the New Forest Pony Breeding Society. The stallions are selected based on many factors including bloodlines, conformation and movement. They are DNA tested and vetted before being selected.
    Even when the number of stallions running out was much higher, and they lived out [in] the Forest all year round, they were moved every three years, so that there was no likelihood of them breeding with their own daughters.”

    Click to access A_Shared_Forest_FAQs.pdf

  12. teageegeepea says:

    Off-topic, but since Greg knows a lot about the second world war, I wondered what his thoughts would be about this:

    • Miles says:

      He doesn’t. He has a vast boomer knowledge and read many NYT-approved bestsellers, or useless perspective books.
      He reminds of Razib Khan’s habit of reading thousands of worthless books.

    • shadow on the wall says:

      The V2 was a terrible investment.
      As waste and self inflicted defeat, V2 was not among the worst of Nazi ideas.
      See here for some more examples.

      (Isn’t it a shame that Mouse and Rat tanks were never built? They would be absolutely awesome.)

      On the whole, this list might be surprising for normies who learned everything about WW2 from Hollywood, but these things are common knowledge among WW2 buffs.
      To find some true facts about WW2 that would surprise Mr. Cochran, you need try harder 😉

      • josh says:

        Can anybody tell me if Hitler and other top Nazi’s really believed in the World Ice Theory and if they did, did it make much difference?

        • shadow on the wall says:

          Hitler’s Table Talk

          Night of 25th – 26th January 1942

          I’m quite well inclined to accept the cosmic theories of
          Hörbiger. It’s not impossible, in fact, that ten thousand years
          before our era there was a clash between the earth and the
          moon that gave the moon its present orbit. It’s likewise possible
          that the earth attracted to it the atmosphere which was that of
          the moon, and that this radically transformed the conditions of
          life on our planet.
          One can imagine that, before this accident,
          man could live at any altitude—for the simple reason that he
          was not subject to the constraint of atmospheric pressure. One
          may also imagine that, the earth having opened, water rushed
          into the breach thus formed, and explosions followed, and then
          diluvian torrents of rain—from which human couples could
          escape only by taking refuge in very high regions. It seems to
          me that these questions will be capable of solution on the day
          when a man will intuitively establish the connection between
          these facts, thus teaching exact science the path to follow.
          Otherwise we shall never raise the veil between our present
          world and that which preceded us.

      • R. says:

        Maus was a meme tank, Ratte was a complete joke. Wastes of effort. But you knew this, right ?

        • shadow on the wall says:

          Bigger is always better, and Maus and Ratte were biggest tanks ever.
          If you ever travel back in time to Nazi Germany, make sure to advise Der Fuehrer to equip his panzer divisions with Maus and Ratte, and scrap all other tanks. Swift and decisive victory guaranteed.

    • Young says:

      I noticed he seemed to include the story of Sherman tank shells bouncing off Tiger tanks as a myth. It wasn’t. Omar Bradley discusses it in his ‘A Soldier’s Story’. I think Eisenhower may have mentioned it in ‘At Ease’ as well. But then he seems to have gathered his information and conclusions from Wikipedia.so I don’t give the comment much weight. Not really worth the time it takes to read it.

    • R. says:

      Makes valid good points, but it’s largely bunk. As in, bullshit said by someone whose has only surface level knowledge of WWII history and is not very bright either.

      Criticizing Germany for not building aircraft carriers in WWII ?

      Criticizing Germany for not having the good luck of having robbed neolithic savages from half a continent of nearly untouched mineral resources ?

      I blame modafinil.

  13. Philip Neal says:

    I wondered if the Roman agricultural authors Columella and Varro might have something to say about this, but no. They have plenty about breeding dogs, and other animals, but it is all about when to mate them. Columella distinguishes between guard dogs, shepherd dogs and hunting dogs, and specifies what to look for when buying them, but he seems to think this just happens to be so and has no concept of selective breeding for particular useful characteristics. Varro knows that dogs from different countries have different qualities but not why. He also discusses how to buy and breed herdsmen: Bastulans and Turdulans are useless but Gauls admirably suited, and head herdsmen need to be literate.

    As to the breeding of herdsmen; it is a simple matter in the case of those who stay all the time on the farm, as they have a female fellow-slave in the steading, and the Venus of herdsmen looks no farther than this. But in the case of those who tend the herds in mountain valleys and wooded lands, and keep off the rains not by the roof of the steading but by makeshift huts, many have thought that it was advisable to send along women to follow the herds, prepare food for the herdsmen, and make them more diligent. Such women should, however, be strong and not ill-looking.

    • gwern says:

      Russell in his summary of Varro & Columella doesn’t mention anything about inbreeding. He does point to one example in Aristotle’s History of Animals where Aristotle retells disapproving anecdotes about incest: https://ebooks.adelaide.edu.au/a/aristotle/history/book9.html

      “The male camel declines intercourse with its mother; if his keeper tries compulsion, he evinces disinclination. On one occasion, when intercourse was being declined by the young male, the keeper covered over the mother and put the young male to her; but, when after the intercourse the wrapping had been removed, though the operation was completed and could not be revoked, still by and by he bit his keeper to death. A story goes that the king of Scythia had a highly-bred mare, and that all her foals were splendid; that wishing to mate the best of the young males with the mother, he had him brought to the stall for the purpose; that the young horse declined; that, after the mother’s head had been concealed in a wrapper he, in ignorance, had intercourse; and that, when immediately afterwards the wrapper was removed and the head of the mare was rendered visible, the young horse ran way and hurled himself down a precipice.”

      • dearieme says:

        They order these matters better in the New Forest. But did they order them better in the 11th century?

        Come to think of it, how did the Franks etc breed the big, heavy chargers that medieval armoured knights needed? I understand, perhaps incorrectly, that in sub-Roman Britain the cavalrymen rode ponies. I don’t know whether they fought from horseback or were effectively mounted infantry.

        You’d think that soldiers, of all people, had an incentive to understand about horse breeding. On the other hand: soldiers, eh? How about the Carthaginians and their war elephants? Or whoever used Dogs of War?

        Would there be particular constraints when horses were parts of teams e.g. in the chariot era of warfare?

    • Steven E. Sailer says:

      Did old time animal breeders keep their knowledge as trade secrets? That might be why old time scholars don’t usually sound well-informed.

      My vague impression is that the rise of scientific agriculture in England either quickly followed or coincided with the publication of Newton’s big book in 1687. Newton had more or less assumed he should keep his breakthroughs as his trade secrets, but the Royal Society guys talked him into publishing, which either set a precedent or was a sign of the times.

      Maybe knowledge of animal breeding in England was secretive up until, say, 1700 and after that it became more public. For example, in the Victorian Era lots of people wrote to Charles Darwin with their observations about animals and he’d include their contributions by name in his books. I don’t think people did much of that 200 years earlier.

      So my guess is that animal breeding did exist before the Enlightenment set us on the road to our publish-or-perish ethos, but it became easier to do well after openness became fashionable. Thus, for example, the explosion in dog breeds in the 19th Century.

      • Jim says:

        I don’t think Newton was deliberately trying to keep anything secret as he readily communicated his results both orally and in writing to Halley and others in response to their questions. But Halley’s enthusiastic reception of Newton’s work greatly encouraged him to undertake the huge effort of writing the Principia.

        Halley also paid for the publication of the Principia.

      • gcochran9 says:

        I think there were a lot of things that everyone knew, except scholars. A bit like today.

        • dearieme says:

          A worthy epitaph for you, Mr Cochran.

          Come to think of it maybe somebody should introduce a degree on “Things known by everyone except scholars”. But then who would teach it?

  14. neunder says:

    Xenophon, Memorabilia, 4.4:
    Hippias: And what is the inevitable penalty paid by those who, being related as parents and children, intermingle in marriage?
    Socrates: The greatest of all penalties; for what worse calamity can human beings suffer in the production of offspring than to misbeget? (36)
    (note 36: Or, “in the propagation of the species than to produce
    misbegotten children.”)
    Hippias: But how or why should they breed them ill where nothing hinders them, being of a good stock themselves and producing from stock as good?
    Socrates: Because, forsooth, in order to produce good children, it is not simply necessary that the parents should be good and of a good stock, but that both should be equally in the prime and vigour of their bodies. Do you suppose that the seed of those who are at their prime is like theirs who either have not yet reached their prime, or whose prime has passed?

    • JerryC says:

      Well, the question was about incest specifically but his answer was about the disadvantages of older parents in general.

  15. shadow on the wall says:

    If you are interested in history of agriculture and animal and plant breeding, check works of Geoffrey Kron from University of Victoria.


    TL;DR: He says that everything that was discovered in British Agricultural Revolution was already practiced by the Romans, only much better.
    The Romans knew everything, ancient Roman agriculture was as good and productive as it possibly could be without powered machinery, chemical fertilizers, insecticides, antibiotics and genetic engineering.
    In some skills, for example fish breeding, Roman practices were still better than we are now in the 21st century.

    BTW, stay clear from his political writings for your own good.
    Professor Kron is progressive anti racist and BLM supporter. He hates American and British white racist capitalists as much as he loves ancient Romans. His looong power point presentations how American and British slavery, racism and capitalism sucks, and how progressive, multicultural and anti racist was the Roman Empire will give an aneurysm to typical person frequenting the HBDIQ sphere.

    • shadow on the wall says:

      Start here, posted separately to defeat spam filter.


      TL;DR: There is no way like the Roman Empire way. Deal with it, barbarian.

      Problems of evidence and interpretation make any account of ancient living standards controversial and hazardous, but our scattered literary and documentary sources and a growing corpus of archaeological evidence are making it increasingly clear that Greco-Roman society was populous, urbanized, and prosperous, with a much broader middle class and a more comfortable lifestyle for ordinary working people than can be attested in most pre-industrial or even early industrial societies, with the possible exception of the city-states of Renaissance Italy or Holland in its Golden Age. Unskilled slaves, common laborers and even some craftsmen, share-croppers or struggling tenant farmers had only a small margin separating them from subsistence, and our sources suggest that approximately 10% of the urban population were in want. Nevertheless, a substantial proportion of the population owned land, houses or apartments, garden plots,and businesses, and the vast majority enjoyed a relatively ample diet, spacious and attractive, often opulent, housing, clothing of good quality, a wide range of consumer goods, access to a large range of commercial and public services, and more options to enjoy art, entertainment, and culture than any society prior to the 20th century.

      Ancient animal husbandry

      Most livestock would not consistently match the improved Greek or Roman breeds until Holland’s Golden Age, or the agricultural revolution of 19th century England.
      Moreover, the extant writings of the Roman agronomists reveal extremely detailed knowledge of the normal behaviour and needs of the principal domestic, and even many wild, species, a preference for intensive mixed farming, based on the principles of convertible husbandry, excellent management of pastures and rangelands, high standards of fodder and forage production, and really remarkable standards of veterinary care, with widespread access to highly trained professional veterinarians (Brill 2011), capable of carrying out most of the surgical procedures widely practiced as late as the mid-twentieth century

      • Steven E. Sailer says:

        The size of sports/theatrical stadiums all over the Greco-Roman world suggests they had a lot of money to burn. What was the first post-classical stadium or theater in Europe or America that could seat over 10,000 people?

        Ballparks for baseball were popular in the U.S. in the late 19th Century, but I’m guessing none reached 10,000 permanent seats until perhaps the 1880s.

    • shadow on the wall says:


      At the height of its development, the Roman Empire enjoyed an agricultural regime as intensive and diversified as any pre-industrial society. The existence of broad and affluent urban markets for a wide range of non-staple foods, a superb transport infrastructure, security of trade and ease of maritime transport stimulated impressive levels of agricultural production throughout the Empire and beyond. The principal agronomic techniques of 17th century Dutch or 19th century English high farming were applied on an impressive scale, with the wide-spread use of convertible husbandry, crop rotations, heavy manuring, drainage and irrigation, pruning and grafting, and improved fodder crops producing remarkably high yields and large livestock.

      Combining convertible husbandry or ley farming with a wider range of fodder crops, better manure management, improved drainage, thorough weeding and improved seed selection, the Romans were able to routinely achieve cereal yields in Roman Italy and Africa of ten to fifteen-fold, comparable to yields for Italy as a whole in the 1970s, and significantly higher than those typically found in Western Europe through most of the Medieval or early Modern period. Our sources give yields for well-managed vineyards which show that Roman winemakers were able to match the performance of their counterparts in mid 20th century France.

      The Romans’ skill in organizing labor, and their remarkable achievement in engineering drainage and irrigation works also played an important role in boosting the productivity of agriculture. It facilitated the thorough exploitation of heavy clay soils and rich alluvial plains, as illustrated by the drainage of the Po valley and its centuriation using an elaborate system of roads and drainage ditches. Further improvements in productivity were likely achieved through the widespread introduction of professionally manufactured iron tools, including ploughs ranging from light ards to substantial wheeled mould-board ploughs with coulters, a range of toothed harrows, and even the vallus, a simple harvesting machine powered by oxen or equids.

    • Jim says:

      Didn’t the Romans make extensive use of slave labor with few signs of any moral concern about it?

  16. Max says:

    Hi Greg,

    It’s been a while since I’ve read you’re blog, but for some reason today I just thought of it. I always knew you were a physics guy, but I didn’t know your background was in optics, which is funny because that’s what I’m considering for grad school. I’m a senior in college studying EE.

    I have no idea if optics is a good field to go into (I was also thinking about RF). Any words of wisdom?


  17. shadow on the wall says:

    Here is yet another example of supposed ancient deep peasant wisdom.
    When in 19th century German settlers arrived in Russia, they started tilling the land as they were used to in Germany, and manuring them.
    The local Russian peasants were aghast, disgusted and absolutely horrified.

    “You filthy Germans are reaally going to put animal shit in the soil? On the fields where you will grow food you will eat? You are really going to eat shit bread made of shit grain, or do you want to sell it to good Orthodox people to poison them?
    We are dumping manure to the rivers and lakes, as our fathers and their fathers did from the beginning of time, because we are clean Christian people. Shall we keep the smelly shit around?”

    These Russians were tilling the land for thousands of years, and they still somehow missed the idea of fertilizing the soil. The uber-rational high IQ contingent here could call it implausible, but it happened.

    Source: memoirs of German settler from Russia, I do not recollect the exact source. If want to prove to me that the wily Kraut just made it up to slander Slavic people, go ahead. 😉

    • dearieme says:

      You might at least tell us at which point in their history the whole of the Russian peasantry lost the knowledge that manure works.

      • shadow on the wall says:

        1/ My anecdote was about peasants living near the German colonies, I have no idea how representative they were about “whole Russian peasantry”.
        2/ If the anecdote is true, the peasants never lost the knowledge, because they never gained it. Traditionally, population in Eastern Europe was sparse and land was plentiful, extensive slash and burn cultivation was the norm. When the land became exhausted, people moved on, burned new patch of forest and started anew.
        3/ The point of this anecdote was that traditional peasant mindset and modern experimental scientific mindset are like day and night.

        • dearieme says:

          On the Steppes of Russia and the Ukraine there weren’t really any trees to slash and burn, except in small patches near the rivers.

          • shadow on the wall says:

            This is was one of the reasons why the peasants were not living in the steppe (the other was that the nomads living there would kill them on sight). The steppes were settled since the 18th century, when the nomads were decisively defeated.
            Anyway, I have no idea if the German settlement in my anecdote was in steppe zone. Most of them were, but not all.

  18. Garvan says:

    Arthur Mitchell, Deputy Commissioner in Lunacy for Scotland in 1865 published a study showing from his own data that 14% of “idiots” were children of close kin. In 44% of families with more than one “idiot” child, the parents were blood relatives. He also noted exceptions where there was considerable regional variation. In one small town in the North-East coast of Scotland 9% of marriages were first cousins, 13% second cousins, but no idiots.

    • dearieme says:

      Eating lots of fish protects you from idiocy? Quick, patent it.

      Or did were idiot babes slung overboard so as not to trouble the Deputy Commissioner later in life?

      Or is it just the statistics of small samples?

  19. Kevin Grant says:

    Mr. Cochran,

    I’ve enjoyed listening to all of your interviews with James Miller (Future Strategist). Do you have any other interviews or lectures available for public consumption (I only found one other on youtube with Luke Ford).

    Thank you,
    Kevin Grant

  20. Pincher Martin says:


    A recently-published book you might be interested in is Genetics in the Madhouse: The Unknown History of Human Heredity by Theodore Porter, a historian at UCLA who has also written a biography on Karl Pearson, as well as a history on the increasing use of statistics in the 19th century.

    Porter claims that the book which made Charles Darwin uneasy about his own marriage to his cousin was Alexander Walker’s Intermarriage; or the mode in which, and the causes why, beauty, health, and intellect result from certain unions, and deformity, disease, and insanity from others, etc.. (Much to my surprise, this book is available on Amazon in a pretty rough format.. I have not read it, and can’t say if it will help you to track down the information you seek.)

    Walker’s book was published in 1839, which also happened to be the year Darwin married has cousin. Darwin was further disturbed a couple decades later after reading work done by the Norwegian alienist Ludvig Dahl. Apparently Norway was known in the 19th century for having an unusually high number of insane people, and Dahl began studying their family background through Norway’s census data. He published his work in 1859, four decades before the eugenicists would begin making similar pedigree charts.

    Darwin was so disturbed by these findings that he finally asked his son, George, to look into it. After much leg work interviewing alienists in England and studying pedigree works like Burke’s Peerage, George’s verdict before the London Statistical Society was “not proven.” But the young Darwin still seemed disturbed by the possibility. Much to my surprise, Francis Galton stood up after the reading and announced before the group that George should not be so cautious in his findings, that he (Galton) knew of many intermarried populations that were “magnificent.”

    • Pincher Martin says:

      To clear up any confusion before it starts, I should make clear that Porter’s book is about much more than my comment above suggests.

  21. Jake Dee says:

    Hi Greg,
    First time commenter long time lurker.
    The earliest reference to the problems of inbreeding among humans that I know of is in Mallory’s Le Morte D’Arthur . It’s highly allegorical of course. Bloodlines are cursed through the sin of incest. Arthur is killed by Mordred his only son, whose mother is his half sister Morgause, who is in turn the result of his father’s adulterous fornication.

    “But ye have done a thing late that God is displeased with you, for ye have lain by your sister, and on her ye have gotten a child that shall destroy you and all the knights of your realm.”
    Morte D’Arthur Book I Chapter XX
    Sir Thomas Mallory (1485)

    The Questing beast is also another allegory for the wrath of GNON. A misshaped abomination (genetic mutant) born of incest which the Knights of the cursed bloodline are doomed to forever chase and never slay.
    It’s all good stuff. I think a socio-biological re-examination of these classics is long over due. The fear of GNON is the beginning of all wisdom.

  22. Young says:

    “The rule to which the church ultimately came was that defined by Innocent III, at the Lateran council of 1215, namely that marriages within the fourth degree of consanguinity are null.” History of English Law Before the Time of Edward I, v. II, p. 406.

    “Already in the seventh century and here in England the church was making her voice heard in these matters. …. “Especially earnest was she [the church] in her attempt to define the ‘prohibited degrees’ and prevent incestuous unions.” v. II, p. 384

  23. Lycurgus says:

    The ancient Greeks frowned on marriages between relatives of the sixth degree (equivalent of second cousin) or closer, and even had a name for the extended family up through this degree of relatedness, although I have forgotten the word. The Church early on opted for the Greek custom over the more lenient marital rules of Moses and codified it into a formal rule. Eighth degree or third cousins were permitted, but there was some disagreement about whether to allow marriages between kin of the seventh degree (equivalent to second cousin once removed) until some time in the 3rd century when the bishops agreed to prohibit those marriages as well. These rules are still observed among the churches of the east.

  24. J says:

    Eliezer was sent by Abraham to Charan (modern day Kurdistan) to bring back a wife for his only son Isaac. Eliezer is given only one requirement: The girl must be from Abraham’s extended family.
    Original Hebrew not only that they were unaware of the disadvantages of inbreeding, they systematically practiced it. Given the fact that malformed and weak babies did not survive in the desert, the system may have produced a cohesive, homogeneous, strong group of peers – Homoioi fighters. Probably in the extremely harsh environments of human past, the disadvantages of inbreeding were not much in evidence.

    • dearieme says:

      Abraham didn’t exist. But you probably can infer that when Genesis was written the Hebrews did like to marry within their extended families. Somewhere in the range 500 – 250 BC, perhaps.

    • gcochran9 says:

      Sure they were. And although in principle, one can reduce genetic load with a lot of inbreeding and culling, it works better in a species that has many (inexpensive) offspring : humans are not well suited to it. And it takes a hell of a long time.
      By the way, any reasonably bright set of pastoralists would know about the perils of inbreeding. It would be hard not to notice it.

      • Ilya says:

        Meaning that the benefits of inbreeding (expressed via familial and clan cohesion) outweighed the costs, at the time. Looking at modern industrial and postindustrial countries, the equation is almost certainly different. Although, when I look at the massive amount of single people and low TFRs, I become doubtful yet again. High-inbreeding, clan-cohesion places seem to have better protection from Western Enlightenment values, including its derivations like feminism, protecting said TFRs. I suppose, it’s a little bit easier for closely related, geographically proximal men to find and keep aligned objectives and to create own binding traditions and rituals, on average.

        • Ilya says:

          I should correct:

          Benefits of arrangements that resulted in inbreeding

          (Vs inbreeding per se)

          A related thing, in the Mari/Ebla civilizations, which existed circa Abraham’s time, it was known that a man could bestow a rank of “sister” to his highest wife.

          Strategic adoptions (including, perhaps, of slave girls) were probably a good way to ameliorate the horrible effects of inbreeding.

          But Enlightenment derived values deride slavery as a whole.

      • gcochran9 says:

        Means no such thing: people aren’t optimized. Many things people do are just stupid.

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