historic mating patterns in japan

readers (luke & jayman) request: what about the japanese? well, we aim to please… (^_^)

the japanese definitely have a history of cousin and endogamous marriages. i’m not sure, yet, how far back it goes (although i’m going to guess pretty d*rn far), but between 1912 and 1925 the consanguinity (first-/second-cousin) marriage rate for japan was 22.4% [pg. 29]. compare that to italy toward the beginning of the twentieth century or to some of the arab countries today. compare it also to the first cousin marriage rate amongst rural english folks in the 1870s: 2.25% (4.5% for the peerage).

but it’s been decreasing ever since (looks like a stock market crash – pg. 30):

by wwii the rate was only about 12.3%, and nowadays it’s like 4% (3.9% in 1983).

imaizumi, the author of the article to which i’ve linked above, also found in the early 1980s that 27% of recently married japanese folks had married endogamously, while amongst the oldest folks studied, 40% had married endogamously [pg. 39]. so endogamous marriages have also declined in japan over the course of the twentieth century. still, more than 1 in 4 japanese entered into an endogamous marriage in the ’80s (or maybe the late 1970s).

seems like the shintoists practice cousin marriage most frequently, followed by buddhists, and is lowest amongst catholics. farmers/fishermen, blue collar workers, the self-employed and people working in services (like transportation) inbreed the most, whereas white collar workers, salesmen and professionals inbreed the least.

note: the type of cousin marriage practiced in japan is mostly mother’s brother’s daughter (mbd) marriage as in china. more on that in the next post on japan. that’s important because mbd marriage amounts to less inbreeding (i think) than the arab type of cousin marriage (father’s brother daughter or fbd marriage) since all of the marriages do NOT occur exclusively in one lineage. in mbd marriage, at least more than one other lineage is involved.

the events of the meiji period obviously shook up the social structures in japan a LOT, but i wonder if cousin marriage/endogamy was officially — or even unofficially — discouraged in any way during that time period. i’m wondering if what happened in europe starting in the early medieval period regarding mating patterns has sorta been repeated in japan, only starting in the nineteenth century. -?-

goes to show, too, how rapidly cousin marriage rates can drop — within one generation in japan cousin marriage rates halved. maybe this could happen only amongst east asians who are big into conformity, but it’s something to keep in mind when trying to imagine what happened in europe in the medieval period, i.e. that things could’ve moved pretty quickly.

more anon!

previously: on the non-violent japanese of today

(note: comments do not require an email. hi there!)

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27 Comments

  1. Ah, finally a post I can speak at length on! Well, if I had time anyways.
    Anyways, it was earlier than the Meiji. The Tokugawa Shogunate policy was to break down the power of regional clans as much as possible, for good reason, as it was the reason why previous governments had fallen. Unfortunately, they did not do a good enough job and a bunch of backwards types from the far south (Satsuma and Choshu) outmaneuvered them. If the Tokugawa hadn’t put such a lock on internal migration and urbanization, they probably would have been more successful. There probably was a whole bunch of immediate elite outbreeding in the Meiji period as the Genro from far south married into the Kyoto aristocratic/imperial class they restored to power, which was mirrored by the movement of common people around and out of the country.

    As for the various categories, very few people identify solely as Shinto, in the Shinto/Buddhist melange that is Japan. Those that do are often families that are related to the maintenance of a particular shrine, which was traditionally handed down in the family (you can see where this goes). Japanese Buddhist priests do marry, but that’s because of the Meiji laws that forced them to give up celibacy. Catholics and Japanese Christians in general are just kind of oddballs and overwhelmingly urban, hence the high outbreeding. White collar workers also tend to be cosmopolitan. Fishermen and farmers have less choice, same with blue collar workers who are mostly with men in their workplace and have to rely on familial/neighborhood connections for dates.

    While there was certainly inbreeding in Japan, it was also probably mitigated by adoption customs. If a man had only daughters and wished to preserve his family line and property, he had the option of “adopting” the husband of one of his daughters, who would give up his last name and ancestral affiliation in order to inherit the property and money of the family he married into. Kept things in the family without keeping it too much in the family.

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  2. “it was also probably mitigated by adoption customs”

    Alan Macfarlane, in “The Savage Wars of Peace,” makes a big deal out of how common adoption was in Japanese culture. As you point out, it allowed families to maintain coherence in property and inheritance while still keeping to a fairly low birth-rate.

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  3. @spike – thanks for the great comment loaded with info! (^_^) i’ll come back to it later after i’ve had my coffee. (~_^) for now, tho…

    @spike – “While there was certainly inbreeding in Japan, it was also probably mitigated by adoption customs.”

    @fred – “Alan Macfarlane, in ‘The Savage Wars of Peace,’ makes a big deal out of how common adoption was in Japanese culture.”

    but you typically adpoted a nephew (not sure if on the father’s or mother’s side) or other family member and married him off to your daughter (if you had one) [pgs. 274-75]…

    “The ideal was for the eldest biological son of the previous head to succeed him. However, circumstances sometimes prevented the realization of this ideal. The eldest son might become incapacitated, be incompetent, or choose some other venture (such as emigrating). In such a case a younger son might inherit the headship. If he had no living son, the head might adopt a male heir, often a nephew or other relative or a daughter’s husband.”

    …so the whole adoption thing was often still a matter of “keeping it in the family” if at all possible. (see also various examples here.)

    the idea was definitely NOT to adopt a stranger if at all possible.

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  4. In general, marrying the first-order nephew off to the daughter was something that only happened in the aristocractic and samurai classes, and even that practice was in decline during the Tokugawa. Usually he was adopted fairly young, and was a younger brother’s spare offspring. For all intents and purposes he would be raised as a son in the household, and sometimes not even told he was adopted. Merchant and artisan families did the husband adoption more often. That was because the daughters married apprentices and employees. If you were the younger son of another poorer larger family, it was one of the few ways you could step up in life. For the family, they had someone trained and personally invested in the business who was already personally vetted. Again, also an artifact of the increasing urbanization and economic development of the Tokugawa period.

    I guess what I’m saying is that increased outbreeding and decline of regional clans were already happening for over 200 years by the time of Meiji, though granted, Life in rural peasant Japanese villages were probably pretty consanguitous until the 1880s to 1950s depending on area.

    Did you read the old Saturday evening post link on the google thing you posted? It was a pretty good overview.

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  5. Interesting stuff with the same recurring patterns
    – multiple lineage level inbreeding as the human/farmer(?) default
    – elite seeking to break down clans
    – urbanization and industrialization acting in a similar way to manorialism *if* the people moving to the cities don’t maintain their marriage links with their home villages
    – potentially quite rapid changes from extreme inbreeding at the beginning of the process tapering off later

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  6. @g.w. – “Interesting stuff with the same recurring patterns
    – multiple lineage level inbreeding as the human/farmer(?) default
    – elite seeking to break down clans”

    definitely farmer/pastoralist default me thinks. and definitely a lot of elites in a lot of places seem to have tried to break down clans … except for the arabs, et. al. hmmmm.

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  7. @spike – “Did you read the old Saturday evening post link on the google thing you posted? It was a pretty good overview.”

    no, i didn’t! i’ll definitely go do so. (^_^) and thanks for all the info. i might have to pick your brain some more at a later time. (~_^)

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  8. “definitely farmer/pastoralist default me thinks”

    it’s not strictly accurate but i think it’s useful to think in terms of two default states
    – pastoral default: single lineage endogamy
    – farmer default: multiple lineage endogamy (2-4 extended families)

    it gets across the idea that pastoralists are striving for maximum endogamy (on a graph their arrow would always point left towards endogamy) whereas the farmers are striving for the maximum amount of endogamy compatible with a minimum number of related allies which seems to be a recurring pattern of 2-4 extended families (which i guess is (or was) the number needed for local equivalent of activities like barn-raising) so the farmers have two balanced arrows one pointing left and one right.

    it’s only conceptual because in reality it’s the same rule i.e. striving for the maximum endogamy compatible with maintaining the minimum number of neccessary related allies for food-getting in that environment. it’s just that the minimum number is lower for pastoralists (on average).

    however i do think that average difference may be significant because i think each extra added lineage has a decreasing effect. given the geometric nature of reproduction: two parents, four grandparents etc, i think there’ll be a mathematical relationship between the size of breeding population and the maximum possible endogamy/exogamy. so if each lineage was 100 then as you go from one to four lineages the breeding population goes
    – 100 to 200: 100% jump
    – 200 to 300: 50% jump
    – 300 to 400: 33% jump

    so i’m thinking the earliest widenings of the circle of relatedness have the biggest jumps in endogamy/exogamy

    so in reality if the pastoralist/farmer difference was
    – pastoralists range from 1-4 linked lineages (average 2.5)
    – farmers range 2-8 linked lineages (average 4)

    then the big gap in the average – if endogamy is directly related to the band of brothers effect – could be part of the explanation for the recurring theme in ancient history of pastoralist invaders conquering settled farmers that goes back to Sumer-Akkad and maybe earlier. the pastoralists are too clannish to unite 99.99% of the time but on the rare occasions when they do they have a major military advantage.

    anyway that idea is mainly of historical interest except it (maybe) illustrates the posssible influence of the move to the cities in places like Japan. if you have a population separated in lots of clannish villages then as they move to the city – as long as their marriage patterns aren’t still tied to their original village (which is often the case but i’m guessing it wasn’t in Japan?) then it’s similar to adding lineages in the earlier example – a fairly rapid increase in exogamy among people in the cities because the first jumps are the biggest.

    TL:DR
    if you start with an agricultural population with a 50% consanquinous marriage rate who then industrialize and move to the cities then the rate might drop to 25% in 2-3 generations (i.e. a huge change) whereas in Holland over the same period the rate might drop from 2% to 1.99% because it already went through the process via manorialism/cousinban.

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    1. @ Greying wanderer “i think it’s useful to think in terms of two default states – pastoral default: single lineage endogamy – farmer default: multiple lineage endogamy (2-4 extended families” This is quite arguable for the Japanese humans, but Japanese quail ard doing exactly the same thing according to Patric Basteson in “Mate Choice.” Wouldn’t you think there is a reason for the reasons?

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  9. @g.w. – “it gets across the idea that pastoralists are striving for maximum endogamy (on a graph their arrow would always point left towards endogamy) whereas the farmers are striving for the maximum amount of endogamy compatible with a minimum number of related allies….”

    that sounds very right, i think. broadly speaking anyway. at least for eurasians. i’m not sure what goes on with pastoralists in africa, tho — the masai, for instance.

    @g.w. – “so i’m thinking the earliest widenings of the circle of relatedness have the biggest jumps in endogamy/exogamy”

    that’s my gut instinct, too. someday when i grow up and learn some math i’m gonna demonstrate that. (~_^)

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  10. @g.w. – “then the big gap in the average – if endogamy is directly related to the band of brothers effect – could be part of the explanation for the recurring theme in ancient history of pastoralist invaders conquering settled farmers that goes back to Sumer-Akkad and maybe earlier.”

    i think so, too! bill hamilton (and also greg cochran) made a similar/related (the same?) point, but i think he (they) missed the point that inbreeding can “jump start” the evolution of altruistic behaviors, i.e. help to rather rapidly increase the frequencies of “genes for altruism” in a population.

    why are the “barbaric pastoralists” soooo altruistic? in part it’s because they’re inbreeding.

    hamilton said: “The incursions of barbaric pastoralists seem to do civilizations less harm in the long run than one might expect. Indeed, two dark ages and renaissances in Europe suggest a recurring pattern in which a renaissance follows an incursion by about 800 years. It may even be suggested that certain genes or traditions of pastoralists revitalize the conquered people with an ingredient of progress which tends to die out in a large panmictic population for the reasons already discussed.”

    hmmmm. so, maybe the settling of pakistanis and turks and somalis in the west will be a good thing in the end.

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  11. @g.w. – “as long as their marriage patterns aren’t still tied to their original village (which is often the case but i’m guessing it wasn’t in Japan?)”

    dunno. will have to find out!

    @g.w. – if you start with an agricultural population with a 50% consanquinous marriage rate who then industrialize and move to the cities then the rate might drop to 25% in 2-3 generations (i.e. a huge change) whereas in Holland over the same period the rate might drop from 2% to 1.99% because it already went through the process via manorialism/cousinban.”

    yeah, that makes sense. i wonder if that’s what happened in japan — could be. i also wonder if that’s what happened/is happening amongst the upper classes in egypt.

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  12. hubchik
    i’m not sure what goes on with pastoralists in africa, tho — the masai, for instance.

    I’m thinking none of this stuff works if you don’t keep track of the lineages so it may be like small underclass areas in the west where over time everyone becomes related by accident but they don’t know who to.

    someday when i grow up and learn some math i’m gonna demonstrate that.

    Yes it’s very frustrating because i have no doubt there are mathematical models already out there that map to sections of this stuff except they’re related to topography or magnetic fields or something seemingly unconnected. If these things are natural biological phenomena then there will be parallels in other fields imo.

    “The incursions of barbaric pastoralists seem to do civilizations less harm in the long run than one might expect. Indeed, two dark ages and renaissances in Europe suggest a recurring pattern in which a renaissance follows an incursion by about 800 years.”

    I think people can get a bit rose-spectacled about this if their ancestors were the barbaric pastoralists. I think 800 years is a massive amount of harm personally.

    inbreeding can “jump start” the evolution of altruistic behaviors, i.e. help to rather rapidly increase the frequencies of “genes for altruism” in a population

    We disagree on this. I think altruistic behaviour is the *product* of two separate things: relatedness and altruistic genes multiplied together, so the more related people are the less strong their altruistic genes need to be. If the human default is inbreeding then i think this makes more sense as an inbred group would then only have needed to develop very small amounts of altruism genes to create an altruistic effect. If so then it’s only when people outbreed that they need to develop *more* altruism genes to compensate for the drop in relatedness and it’s this that explains how those people can then come to display altruistic type behaviour towards non-kin.

    so, maybe the settling of pakistanis and turks and somalis in the west will be a good thing in the end.

    When the Mongols conquered China the death toll wasn’t just military related there were mass famines and plagues as a result of things like their irrigation system breaking down – and that was a drop in carrying capacity from a much lower base than the West has now. So i think the consequences will be in the ballpark of “Revelations.”

    i also wonder if that’s what happened/is happening amongst the upper classes in egypt.

    Yes i think so. If you followed the Arab spring events you could see the clear distinction between the upper middle class element and the mass element. When the upper middle class element is described as westernized it’s not what people think it means imo. It’s not cultural – at least not as the cause – it’s that that section of the population are biologically freer of their traditional culture.

    Reply

    1. @ Greying Wanderer “If so then it’s only when people outbreed that they need to develop *more* altruism genes to compensate for the drop in relatedness ” That’s one of a number of good points. My social interactions are mostly limited to driving my car. I am a rather aggressive but on the whole altruitic driver. My opinion of other drivers is that a lot of them are anti-social. When somebody does something I find regrettable, such is drive his truck up fast behind a stopped car in heavy traffic and then suddenly swerve into the only available place in the alternative lane (it’s sort of like the “discovery check” in chess) or breaks the law and risks his neck to get in front of another car then only to slow down, I think “What earthly pressure, genetic or otherwise, is there for him not to act like that?” We’ll need more altruism. Whether we get it is another question. The historical record does not reassure.

      “When the upper middle class element (of Egypt) is described as westernized it’s not what people think it means imo. It’s not cultural – at least not as the cause – it’s that that section of the population are biologically freer of their traditional culture” That sounds right to me and it sounds important. I wonder where this phenomenon and our own apparent misunderstading of it leads.

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  13. @g.w. – “Yes it’s very frustrating because i have no doubt there are mathematical models already out there that map to sections of this stuff except they’re related to topography or magnetic fields or something seemingly unconnected. If these things are natural biological phenomena then there will be parallels in other fields imo.”

    (^_^) actually, evolutionary biologists do talk in terms of “fitness landscapes.” (^_^)

    i feel silly that i haven’t thought about this before ’cause i’m always on about how stock market trends must be able to be explained by some sort of mathematical model on animal herding patterns … why didn’t i think of altruism and some other phenomenon? duh! thanks for mentioning it. (^_^)

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  14. @g.w. – “I think 800 years is a massive amount of harm personally.”

    “So i think the consequences will be in the ballpark of ‘Revelations.'”

    well, you (and everyone around here) know/s that i’m a conservative chick by nature, so i’m not big into mass immigration. (^_^)

    however, on the one hand, i feel that i have to admit the logical conclusion that, at least in europe, things turned out pretty durned ok after the barbarian german (and other) tribes invaded areas of europe that hadn’t been a part of their original territory. after 800 years or so. so, who knows? maybe … maybe … if europe today is invaded by some other group, things will again turn out to be pretty durned ok … after 800 years or so. i feel that has to be acknowledged.

    on the other hand, what makes me pause — with a capital “P” — is that we can’t KNOW that for sure, so why mess with something that’s already so good and works so well? not to mention the fact that we’re talking about the future of my genes here, so … you know … err on the side of caution and all that.

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  15. @g.w. – “I think altruistic behaviour is the *product* of two separate things: relatedness and altruistic genes multiplied together…”

    i am just about to write a post on that! i thought that i thought of it myself, but maybe it was you that persuaded me of this. (^_^)

    @g.w. – “…so the more related people are the less strong their altruistic genes need to be.”

    i hadn’t thought of that! not exactly, anyway. interesting! thanks!

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  16. @linton – “I wonder where this phenomenon and our own apparent misunderstading of it leads.”

    this is a major, MAJOR problem in the west (in the world) today: the fact that most people, most importantly our so-called leaders, don’t understand (and don’t want to understand) human biodiversity, i.e. that different human populations are fundamentally different by nature. the result is unbelievably wasteful (in terms of human lives) actions like “bringing democracy to iraq, afghanistan, etc.” (i know that’s prolly not what we’ve really been doing, but many people actually do believe all this democracy stuff.)

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  17. “however, on the one hand, i feel that i have to admit the logical conclusion that, at least in europe, things turned out pretty durned ok after the barbarian german (and other) tribes invaded areas of europe that hadn’t been a part of their original territory. after 800 years or so. so, who knows?”

    I know what you mean and part of me kinda likes the idea of my ancestors being very tough spiky haired face-tattooed barbarians but i think the european case was a bit of a fluke mostly for the sort of reasons you’ve been illustrating. I think barbarian pastoralists generally bring in a large dose of feirceness genes which is both good and bad and in the european case the larger skull size might have been significant but in most cases the result is more like the Arab and Mongol conquests than the Germanic one – 800 years of stagnation followed by another 800 years of stagnation.

    I could be wrong though and i am definitely biased due to experience with the worst aspects of Somalis so take that into account too :)

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  18. Whilst first cousin marriage is the most common form of marriage in pre-modern societies and was not at all rare in even urban areas in pre-war Japan, it has become a rarity in this modern, mass education, mobile age. While obviously legal (just barely) it has been driven out by a mass inculcation of the belief that first cousin marriage carries an unacceptable risk of birth defects, should there be children. Indeed, the prime minister and his wife’s parents vehemently opposed the two marrying.

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  19. I had a thought inbreeding among the Japanese. Though the Japanese appear to be fiercely nationalistic, they also appear to be much less clannish that the Chinese. From what I gather here, the level of outbreeding in Japan has been somewhat higher than in China, but does that explain the difference? But, as you’ve noted, one of the traditional goals of MBD marriage has been to cement alliances between two lineages. But what if in Japan, such long stretches of marriage between two clans didn’t go on for as long as they did in China? It’s a complete guess, but perhaps it could explain a few things?

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  20. here’s a comment from an anonymous reader who sent this to me via email. thanks, anonymous! [h.chick]:

    Interesting discussion.

    Let me add two points:

    1. The practice of adoption was more common than many people here seems to think. Among the urban classes (both commoners, clergy and aristocracy) it was not uncommon for a business owner to adopt a man from outside when he had no “useful” heirs of his own. This man could then be married to “cousin” (niece of the original patriarch).

    The practice of “deshi”, or apprentice, made this even more common, as accomplished deshi of famous artisans would take the name/business of the original artisan with or without marrying into the family. This practice still exists today.

    2. The classes working the lands (farmers and other people involved in agriculture) had their own ways of avoiding inbreeding: bath houses and festivals. Mix sex bathhouses, public nudity and night time festivals were more or less socially acceptable places to get pregnant quick, if your husband couldn’t or would’t put up. This practice ended largely in the Meiji period (1868-1912) when foreigners would be shocked at going ons at some famous festivals (sadly, these festivals although mostly still in existence are now devoid of random sex). Also, since Japanese have very similar appearances even today (EVERYONE has the same hair color and eye color for example), a child made on the sly would not be difficult to hide in plain sight. Hence the old joke: “I say, that is a lovely looking baby boy. Is your neighbor Mr Suzuki by any chance?” (or as the western version goes: “Cute kid. By the way, Is your milkman called Stevens?”).

    And on a final note, but so far just a hunch, is the fact the modern blood group testing has made outing children as the results of affairs much easier might have led to modern Japanese (or more specifically post war Japanese) to be MUCH more conservative and careful in their affairs. Hence the universal practice of adding the question “what blood group are you?” right after inquiring after name and hometown, among present day young people.

    No academic experience in the subject but plenty of field experience as (one of very few!) legally resettled immigrants to Japan.

    Reply

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