japan – reversal of fortune?

a couple of months ago, greg cochran wrote about how a population (any given population) might raise its average iq quickly — like over two or three generations. one possible method, he suggested, was to quit inbreeding. here’s what he said:

“I’ve been thinking, off and on, about sudden changes in the cognitive abilities of populations: groups low suddenly scoring much higher or lower on a time scale too short to be explained by selection: say, three generations or less…. I can think of two perfectly feasible strategies that *would* cause significant one-generation increases in intelligence, in certain populations. Iodine supplementation, in places where it’s short, has a big payoff…. The other practical, low-tech strategy would be stopping cousin marriage. The next generation would be in much better shape, since the children of first cousins take a substantial IQ hit – maybe six points or so.

i think i may have stumbled across an example of a population rapidly dropping cousin marriage and, also very rapidly, gaining iq points.

japan.

yesterday, i was working on a completely different post about japan and cousin marriage, when i rediscovered this [pg. 30] (click on chart for LARGER version):

japan consanguinity rates - decline

that’s the decline in the average national consanguinity rates in japan from 1947 to the early-1980s. but the consang rates were even higher in the 1910s-1920s at 22.4% [pg. 29] (and who knows how high the rates might’ve been even further back?), so the chart above should look something more like this (pardon my crayola — and note that i just eyeballed it — click on chart for LARGER version):

japan consanguinity rates - decline - crayola 02

when i rediscovered this yesterday, i remembered what greg had written, and got to wondering if there were any historic data for japanese iqs and if there’d been any changes in those iqs over time. so i googled (as one does) … and found this:

The Rise of National Intelligence: Evidence from Britain, Japan and the U.S.A. [pdf] – lynn and hampson.

from that article [pgs. 27-31]:

“It has been possible to find five studies providing evidence on the secular trend of intelligence in Japan for the post World War II period….

“(1) Ushijima’s study (1961)….

“Here the Ushijima intelligence test was administered to 1365 children in 1953 and to a comparable sample of 1370 children in 1960 with the objective of determining any change in the mean over this relatively short period. The children were aged 9-15 years.

“(i) All age groups show a rise in scores for all abilities. The overall mean increase was 0.66 standard deviations, the equivalent of 9.9 IQ points, and representing an IQ gain of 14.1 IQ points per decade. This is of course a very considerable increase and much greater than anything found in either Britain or the U.S.A.

“(ii) The IQ increases are in general greater among the younger age groups than among the older….”

see my crayola chart above. kids who were fifteen in 1953 would’ve been born way back in 1938 when the consang rates were above 15% — maybe 17 or 18% (remember, i just eyeballed it, so this is a complete guess really) — while kids who were nine in 1953 would’ve been born in 1944 when consang rates were hovering right around 15%, in other words lower. same for the later cohort from 1960: fifteen year olds would’ve been born in 1945, nine years old in 1951. the younger the kids in the cohorts, the less chances their parents were related.

more from the article…

“(2) Kaneko’s study (1970)….

“Kaneko’s invetigation of a possible rise in the scores on this test was carried out in 1963….

“Hence the mean IQ in these schools has risen 10.38 IQ points over the 9-yr period … represents an IQ gain of 11.4 IQ points per decade. This figure is evidently broadly similar to the rise of 14.1 IQ points per decade for 1953-1960 found by Ushijima and confirms a very considerable rate of IQ gain in Japan in these early post World War II years.

“(3) Sano’s study (1974)….

“It will be seen that in all samples there were considerable increases in mean IQ from 1954 to 1972. The increases appear to be a little greater among the city children than among those from the prefrecture. When the results for 10- and 11-yr olds are combined, city children gained 18.04 IQ points and prefrecture children 15.07 IQ points….”

that the city children had greater gains than the rural kids is not surprising if inbreeding is the factor making the difference here. even up to the 1980s, consanguinity rates have been quite a bit lower in urban areas in japan as compared to rural areas (see table in this post for example). (more on this soon in that upcoming post on japan.)

“The average of the two gains is 16.56 IQ points, representing a gain of approx. 9.15 IQ points per decade for the entire sample.

“Sano also considered the question of whether the IQ gains in Japan have been increasing at a constant rate. For this he used Kaneko’s 1964 data which were available for two of the schools. He calculated that the increase in mean IQ was 10.47 points for 1954-1963 and 3.42 for 1963-1972…. ([I]t will also be noted that the gain of 10.47 IQ points for 1954-1963 is closely similar to Kaneko’s figure of 10.38 for the same period.)

“It is apparent therefore that there was a considerable deceleration in the rate of increase in intelligence over the period 1954-1972….”

again, see my crayola chart. the decline in cousin marriage rates is much sharper in the decades preceding 1954 than during those preceding 1963. in other words, there was a deceleration in the reduction of cousin marriages over time, so perhaps we shouldn’t be surprised at a deceleration in the increases in iq over time.

“(4) Wechsler studies….

“Thus after making these adjustments we have Japanese mean IQs of 101.9 for 1951 and 107.4 for 1975. Hence over this 24-yr period (1951-1975) the Japanese mean IQ increased by 5.5 IQ points relative to the American IQ…. This represents a Japanese IQ gain of 5.75 IQ points per decade. This rate of increase for the period of 1951-1975 is somewhat less than Sano’s result of a 9.15 IQ point per decade increase over approximately the same period (1954-1972)….

“A second Japanese study using the WISC and WISC-R is also available (Anon, 1981)…. This gives a rise of 20.03 IQ points over the 24-yr period, making 8.34 IQ points per decade….”

lynn and hampson conclude:

“The conclusion of the Japanese studies is as follows. Two studies of the early post World War II period show substantial IQ gains of 9.9 and 11.4 IQ points per decade. Three studies of a longer period from approx. 1950-1975 show lower IQ gains of 9.1, 8.3 and 5.7 IQ points per decade, giving an average gain of 7.7 IQ points per decade. Since the early part of this period was characterized by a greater rate of gain, it appears that since around 1960 the IQ gains in Japan have decelerated to approx. 5 IQ points per decade….

“It is not particularly surprising that the Japanese gains should have been the greatest of the three countries. Japan was a relatively underdeveloped country in the 1930s with a per capita income about one eighth of that of the U.S.A.”

but the country was probably relatively underdeveloped because the japanese had a lower average iq at the time, and it’s since increased phenomenally … due to the sharp and rapid decline in inbreeding in japan? and so has their economic success obviously.
_____

i’d be curious to know two things:

– why did the japanese quit marrying their cousins? was there some official policy out there discouraging it — as part of their general modernization, “be more like the westerners” move? did the people just naturally adopt it as part of that westernization package? was it connected to christianity in japan? (japanese catholics historically had lower first cousin marriage rates than other religious groups — i’ll get to this in my upcoming post on japanese cousin marriage — the one that i was working on yesterday!). was it related to industrialization and urbanization? all of the above? none of the above?

– has something similar happened in china and/or korea (or elsewhere for that matter — i mean in modern times)? the cousin marriage rates for china are reportedly very low — today — but i’m pretty sure they were much higher in the past — even the recent past (see mating patterns in asia series below ↓ in the left-hand column), but i don’t have as good data for china as what i’ve presented here for japan. but inquiring minds want to know!

see also: Reversal of Fortune

previously: historic mating patterns in japan

(note: comments do not require an email. cool japanese people!)

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51 Comments

  1. The obvious objection is that even consang. rates of 20% means that the other 80% are not marrying their first cousins and taking a substantial IQ hit…

    (Although I suppose it also depends on which classes do consang. marriage. If it’s more of an upper class thing, as it typically is, then Japan could indeed have suffered from a relative deficit of high IQ elites until recent times).

    Reply

  2. @anatoly – “The obvious objection is that even consang. rates of 20% means that the other 80% are not marrying their first cousins and taking a substantial IQ hit…”

    what i would wonder, though, is what sort of rates did they have before 1910-1920? also, lots of endogamous (local) marriages in japan — even very recently (27% of younger japanese in the 1980s, 40% of older people) — that’s IN ADDITION TO the consanguineous marriages (1st & 2nd cousin) — which means they’re prolly marrying third, fourth, fifth cousins. that probably doesn’t help if you’re already in an inbreeding population.

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  3. The effects of third cousin marriage are probably unnoticeable. Even 2nd cousin doesn’t cause too much trouble. The key number is the autozygosity, the fraction of of the genome that is identical by descent. This drastically increases your chance of having two copies of a deleterious mutation.

    Average autozygosity is 1/16 for first cousins, 1/64 for second cousins, 1/256th for third cousins. .

    A reasonable estimate for the IQ depression associated with first cousin marriage is 6 points. Probably varies, depending on the genetic background/history of the population.

    So outbreeding cannot be the main reason for increasing IQ scores. But it may be part of the reason. I nominate eating a lot fewer fish heads.

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  4. @gcochran9 – “The effects of third cousin marriage are probably unnoticeable. Even 2nd cousin doesn’t cause too much trouble.”

    even in a regularly inbreeding population? i mean, shouldn’t there be some sort of … cumulative effect? average autozyosity is 1/16 for first cousins in an oubreeding (or randomnly breeding) population.

    @gcochran9 – “I nominate eating a lot fewer fish heads.”

    but the fish brains are one of the most nutritious parts of the fish! it’s what the grizzlies eat preferentially. (~_^)

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  5. @gcochran9 – “So outbreeding cannot be the main reason for increasing IQ scores. But it may be part of the reason.”

    you’d think it must be at least part of the reason — otherwise the coinciding patterns in the numbers — rapid declines then tapering off, younger kids in the cohorts having higher iqs vs. the older ones — seem awfully coincidental.

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  6. Here’s an example. A recent study in PLOS genetics found that the odds of schizophrenia went up by 17% for every 1% increase in autozygosity. The offspring of a first-cousin marriage would have double the schiz risk. Third cousin, 7% more.

    There are populations that have pretty high autozygosity because of a limited founding population. But if that happened a long time ago, as with Amerindians, selection would reduced the number of bad mutations floating around. The worst kind of autozygosity must be recent autozygosity, just a couple of generations back.

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  7. @gcochran9 – “A recent study in PLOS genetics found that the odds of schizophrenia went up by 17% for every 1% increase in autozygosity. The offspring of a first-cousin marriage would have double the schiz risk. Third cousin, 7% more.”

    yes, but how about the offspring of a first-cousin marriage in which the parents were also the offsprings of first-cousin marriages, and so on, and so on? do that enough — like some pakisantis (and probably the arabs) — and you wind up with first-cousins not having average autozygosities of 1/16 but 1/8 instead. (not saying the japanese ever reached those sorts of levels, tho — prolly not.)

    here’s a possible example: Consanguinity effects on Intelligence Quotient and Neonatal Behaviors of Ansari Muslim Children [pdf]

    rural ansari iq:
    non-consanguineous – 78.5
    consanguineous – 69.2

    suburban ansari iq:
    non-consanguineous – 93.0
    consanguineous – 78.6

    those are 9-14 point spreads. 9 is close to the suggested average you gave of 6 for the hit on iq of inbreeding depression, but 14 is more than double. i don’t think the ansari should have any founder effect issues.

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  8. @hbd chick “that’s the decline in the average national consanguinity rates in japan from 1947 to the early-1980s. but the consang rates were even higher in the 1910s-1920s at 22.4% ” er, uh, excuse me, but would it be rude to point out that fertility is also low in Japan? That they’re dying? That the work force is already falling? Maybe there is an effect such as you suggest. There should be a best overall strategy. After twenty years of looking at consanguinity and ten of looking at fertility I couldn’t even give informal adice, you know.

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  9. as greg notes, shared genes decrease by the square the farther you go horizonatlly. It drops off fast. However, I think you can get some of those extra points you’re looking for ma’am – an eighth or a quarter of them, by traveling backward in genetic time instead of sideways. 22.4% consanguinity does not only mean one out of five weddings of your classmates were consanguinous, but one out of five of your ancestors were joined to a cousin. That also will disappear quickly, but it’s something.

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  10. I’d guess a combination of decrease in inbreeding and better nutrition is primarily responsible. after all, the Japanese also got taller after WWII as well. For all the furious denunciations of the Western diet (some of it justified), overall Japanese health did improve after they adopted portions of it.

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  11. @toddy cat – “after all, the Japanese also got taller after WWII as well.”

    inbreeding makes you shorter, too. (~_^)

    but, yeah — i’m sure better nutrition goes a long way to increasing both iq and height. and i agree that it’s probably not switching to outbreeding alone that effected all these changes in the japanese population.

    btw, did the japanese really have such a poor diet before us westerners turned up with our meat and potatoes (and milk)? i mean, what’s wrong with fish? i thought it was supposed to be awfully good for you. did they just not have enough? and milk? i know some of them can tolerate milk, but the majority are lactose intolerant, no? how would the introduction of milk have helped? just wondering. (i know you didn’t mention milk, but i just read about milk in japan somewhere else … coming up in a post later today (^_^) ).

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    1. @hbd chick “inbreeding makes you shorter, too. (~_^):” I have no data but my won observation but I have long thought that. When you commence outbreeding height zooms upward. Apparently a generation later weight goes up, too. On the other hand, the fattest people in the country apparently are also the poorest, which doesn’t compute so far as I can figure it. Maybe it really is lack of gyms and aeobic instructors and vegan enthusiasts spreading guilt and so forth. But I really think the height thing is real. On the other hand, very short men often strike me as incredibly bright, which is not what I’m hearing here.

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  12. @avi – “as greg notes, shared genes decrease by the square the farther you go horizonatlly. It drops off fast.”

    but not as fast if you come from a regularly, long-term inbreeding population. or, rather, not down to the same levels as in an outbred population (i guess that’s what i’m trying to say).

    the inbreeding coefficient of first cousins is 6.25% (±2.4%), but in some pakistanis, for example, a population that has been practicing fbd marriage for ca. a millennium anyway, the inbreeding coefficient can be twice that. that must be because of the repeated first cousin marriages.

    so the shared genes drop off fast-ish in inbred populations — but not as fast as in outbreeding populations.

    @avi – “22.4% consanguinity does not only mean one out of five weddings of your classmates were consanguinous, but one out of five of your ancestors were joined to a cousin.”

    exactly! (if the rate was the same in the past, of course.)

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  13. You people obsess with your obsessions and are deaf to what Greg is saying. Japanese diet includes much fish and there is a cultural preference for consumption of some body parts proven to contain higher levels of mercury, such as fish heads. When the Japanese adopted Western diet like eating meat after universal conscription, public health improved and also the mercury intake decreased. I’d like to add to Greg’s observation, that Japan is the home of 水俣病 – the Minamata mercury poisoning, but it may be stupid (probably because I indulge in gefilte fish and my family-lore says that eating fish brain makes one smart!).

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  14. @j – “When the Japanese adopted Western diet like eating meat after universal conscription, public health improved and also the mercury intake decreased.”

    you got a reference for that?

    @j – “…Japan is the home of 水俣病 – the Minamata mercury poisoning….”

    that was a very specific case. i mean, it happened … in (and around) minamata … not all over japan (afaik).

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  15. @luke – “Did Japan’s traditional marriage patterns differ from the Chinese?”

    dunno for sure … yet! (~_^)

    pretty certain they both went for cross-cousin, maternal cousin marriage generally. neither group big into fbd marriage (the chinese disapproved of it strongly). don’t know much more beyond that. still need to dig more into the chinese mating patterns….

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  16. I’m not sure if cousin marriage is the factor here. Apparently Korea has a long tradition of banning close marriages. Korea has a similar IQ level to that of Japan. And Japan is wealthier than Korea and modernized economically earlier than Korea did.

    This article discusses Korea’s tradition against “intra-clan” marriages:

    “Changing Lifestyles : S. Koreans Shake Family-Tree Rules : * Thinking about getting married? In Seoul, you may be out of luck if you two had a common ancestor, say, 600 years ago.”

    http://articles.latimes.com/1992-03-17/news/wr-3766_1_common-ancestor

    “Businessman Kim Eui Kyong and his one-time student, Kim Kyoung Sun, made one basic mistake.

    They fell in love before checking their family tree.

    Sure they had the same surname–but Kim in Korea is like Smith in the United States, only more so. More than one in five South Koreans are Kims. It turned out that Eui Kyong and Kyoung Sun shared a paternal ancestor who lived about the time that the English poet Geoffrey Chaucer was writing his Canterbury Tales, back in the 14th Century. Their common blood amounted to one drop in 14 million or so.

    No matter. In South Korea, it is too much.

    For here, uniquely, two people with a common ancestor anywhere in their paternal lineage–no matter how far back–are forbidden by both law and custom to marry. China, where the idea of banning intra-clan marriages originated, abandoned the practice at the turn of the century. Communist North Korea abolished a law similar to the south’s in the late 1940s, although Koreans there reportedly still frown on clan marriages.

    But that was little consolation to the Kims, who risked official sanctions, financial penalties and social ostracism to marry illegally.”

    —–

    “Article 809 of South Korea’s Family Law bars marriage between any man and woman “with the same family name and the same place of origin”–members, in other words, of the same clan, believed to share a male ancestor. Article 815 bars marriage through four generations if there is a common ancestor in the maternal lineage of one or both of the partners.

    Marriages that run afoul of either of those articles cannot be registered, and are therefore not legal. In practical terms, that means that husbands can’t claim a tax exemption for their wives, and any children of the union are technically illegitimate.

    Parents sometimes disinherit children who marry within the clan, and other social pressures exist. Kim said he fears that a rival at work in one of South Korea’s mid-sized conglomerates might use his marriage to discredit him.

    The social pressures are so widespread here that some intra-clan couples separate rather than face them. Suicides, too, have occurred.

    Confucian scholars, who insist that the tradition and the law exist to prevent defective births from a union of close relatives, liken intra-clan marriages to “the behavior of dogs and alley cats.” But that argument clearly is a sophistry to preserve reverence of paternal lineage.”

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    1. @Tim ” Article 815 bars marriage through four generations if there is a common ancestor in the maternal lineage of one or both of the partners” That is truly amazing. According to my numbers that is survivable, but it seems to take the ban on cousin marriages above and beyond the call of madness. The must be doing and awfully good job of keeping track of people. Their fertilty of course is a disaster now days just like the rest of the rich world, but the didn’t drop below 2 children per woman unitl about 1984. Then they went meta stable like the rest of the rich world with birth rate not falling so fast but age at first marriage rising. One can recognize the pattern, but I don’t think anyboy realy understands it. I sure don’t

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  17. @tim – oh, interesting! thanks! and thanks for the link. (^_^)

    “For here, uniquely, two people with a common ancestor anywhere in their paternal lineage–no matter how far back–are forbidden by both law and custom to marry.”

    that still leaves room for maternal cousin marriage though. according to the article, the koreans picked up the idea of banning marriage in the paternal line from china. and it is correct that — traditionally in china anyway (i don’t know how the chinese feel about it today) — you couldn’t marry someone with the same surname as yourself in china. BUT you could marry someone from your mother’s clan, i.e. a maternal cousin — which is what happened — a LOT (not so much anymore apparently).

    Reply

  18. Here’s your answer:

    Article 809 of South Korea’s Family Law bars marriage between any man and woman “with the same family name and the same place of origin”–members, in other words, of the same clan, believed to share a male ancestor. Article 815 bars marriage through four generations if there is a common ancestor in the maternal lineage of one or both of the partners.

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  19. In any case, both laws were abolished in 1998, I believe.

    Almost none of the young people who have reached legal age are even aware that such draconian laws used to exist. Such is the pace of cultural change in S. Korea. Who could have predicted Gangnam Style ten years ago? :-p

    Reply

  20. First, second, and third (!!) cousin marriages are still illegal, so I wouldn’t worry about anything yet.

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    1. @mistraevus ” First, second, and third (!!) cousin marriages are still illegal, so I wouldn’t worry about anything yet.” What a difference point of view makes. Evidently capable and interested people look at the same data and see quite different things. I would have said the demographics of Korea suggest “I wouldn’t worry about anything any longer. To paraphrase the constable in Young Frankenstein, panic is an ugly thing, but maybe it’s time for a good old fashioned panic.”

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  21. “btw, did the japanese really have such a poor diet before us westerners turned up with our meat and potatoes (and milk)?”

    I can’t really say, I’m certainly no expert, but I understand that protein and fat consumption went up significantly after WWII. Fish is good for you, but I’d be willing to bet that white rice was the predominant staple of the diet prior to WWII. How much fish did your average Japanese citizen get in the 1930’s, for example? I’ll have to find the source, but I’ll bet not all that much. As for milk, I think that most Japanese are lactose intolerant, so I’m not sure how much of a role that played. And certainly, thae pre-WWII Japanede diet wasn’t THAT bad, just not as good as it is today.

    “You people obsess with your obsessions”
    Yes, but if I didn’t obsess about my obsessions, they wouldn’t be my obsessions, now would they? There. I’ve run rings around you logically (as Monty Python would say)… : )

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  22. Cochran may be right about it being dietary.

    Japan had a problem with the disease “beriberi” through WWII. Beriberi is caused by thiamine (vitamin b1) deficiency and results in weight loss, weakness, impaired senses, and other debilitating effects. Polished white rice lacks thiamine, so too much white rice in the diet can lead to beriberi. Also, raw fish contains an enzyme called thiaminase that inactivates thiamine, so sushi would have made it worse. Thiamine deficiency also can cause Wernicke’s encephalopathy, which leads to impairment of short-term memory and confusion.

    There’s a book about this called “Beriberi in Modern Japan
    The Making of a National Disease”. Here’s the blurb for it: http://www.urpress.com/store/viewItem.asp?idProduct=14002

    “In modern Japan, beriberi (or thiamin deficiency) became a public health problem that cut across all social boundaries, afflicting even the Meiji Emperor. During an age of empire building for the Japanese nation, incidence rates in the military ranged from 30 percent in peacetime to 90 percent during war. Doctors and public health officials called beriberi a “national disease” because it festered within the bodies of the people and threatened the health of the empire. Nevertheless, they could not agree over what caused the disease, attributing it to a diet deficiency or a microbe.

    In The Beriberi in Modern Japan, Alexander R. Bay examines the debates over the etiology of this “national disease” during the late nineteenth and early twentieth centuries. Etiological consensus came after World War I, but the struggle at the national level to direct beriberi prevention continued, peaking during wartime mobilization. War served as the context within which scientific knowledge of beriberi and its prevention was made. The story of beriberi research is not simply about the march toward the inevitable discovery of “the beriberi vitamin,” but rather the history of the role of medicine in state-making and empire-building in modern Japan.”

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  23. Saint Francis Xavier, in his first report on Japan, examines Japanese intellligence:

    “The Japanese are led by reason in everything more than any other people, and in general they are all so insatiable of information and so importunate in their questions that there is no end either to their arguments with us, or to their talking over our answers among themselves.”

    So there were no stupid even then. However, he considered the Chinese even more Intelligent.

    BTW, Francisco learned Japanese language in a few days and thought it was very easy,

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  24. Toddy:

    “You people obsess with your obsessions” Yes, but if I didn’t obsess about my obsessions, they wouldn’t be my obsessions, now would they? There. I’ve run rings around you logically (as Monty Python would say)… : ) ”

    It was for running logic rings like yours that 501 Athenians condemned Socrates to drink poison. Now, if he didnt drink it from his cup, it would not be “his” cup, would it?

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    1. @j “Now, if he didnt drink it from his cup, it would not be “his” cup, would it?” You are saying they made the guy provide his own cup? Gee that’s harsh.

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  25. @pender – “Cochran may be right about it being dietary.”

    a dietary explanation would certainly fit since there does seem to have been a LOT of poverty in japan in the late-1800s/early-1900s and poor nutrition usually goes along with that. i still think that the uneven rate in the increases in iq that rather match the uneven rate in the decreases in consanguinity seem awfully coincidental. but maybe they’re just that.

    @pender – “Also, raw fish contains an enzyme called thiaminase that inactivates thiamine, so sushi would have made it worse.”

    oh, interesting! i had no idea.

    you know, sushi in its current form (completely raw fish) doesn’t go that far back, although it was certainly around in the 1800s (and maybe a bit before? — i wonder how regularly it — and/or sashimi — was eaten in the 1800s?). previous to the raw fish version, sushi was fermented — a process about which i know nothing. any ideas if that process might’ve gotten rid of the thiaminase?

    thanks for the book link! (^_^)

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  26. @pender – “Polished white rice lacks thiamine, so too much white rice in the diet can lead to beriberi.”

    @toddy cat – “I’d be willing to bet that white rice was the predominant staple of the diet prior to WWII. How much fish did your average Japanese citizen get in the 1930′s, for example?”

    well, that’s the thing — too much rice and not enough fish (or other proteins) does not a good diet make. fish is really, really good for you — and the fish heads really are the best part on the fish (as long as they’re not poisoned with mercury) along with the caviar — most dha in those parts (the grizzlies really do eat the heads and the caviar and leave the rest of the fish behind during the salmon runs in alaska!). but you, of course, have to have enough fish (or other proteins) in your diet. maybe there wasn’t enough to go around in nineteenth century — and earlier — japan.

    (then i’d have to ask why, though….)

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  27. @misdreavus – “Here’s your answer: Article 815 bars marriage through four generations if there is a common ancestor in the maternal lineage of one or both of the partners.”

    ah ha! thanks! however, that civil code is from 1958 (iwitbb**) — wonder what the traditions/regulations were before that? could’ve been along the same lines — might not have been though. hmmmm.

    @misdreavus – “First, second, and third (!!) cousin marriages are still illegal, so I wouldn’t worry about anything yet.”

    (^_^)
    _____

    **iwitbb=if wikipedia is to be believed.

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  28. @chris – “I wonder if the fact that polygamy [polygyny] became illegal in Japan after 1945 would have contributed towards Japan becoming a more outbred population….”

    interesting! yes, that ought to increase the outbreeding, too. polygamy certainly makes more people in the community related to one another in some way (more half-siblings and half-cousins, etc., etc.).

    thanks for the link! (^_^)

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  29. “and representing an IQ gain of 14.1 IQ points per decade.”

    Bejabbers!

    Well i think this is a bullseye – and yes diet as well blah blah.

    .
    “in other words, there was a deceleration in the reduction of cousin marriages over time, so perhaps we shouldn’t be surprised at a deceleration in the increases in iq over time.”

    If it’s a shedding of load then there’s likely to be diminishing returns. (Personally i think this is partly what the Flynn effect is measuring and the populations with a near-zero Flynn effect are those who have already shed the load that is sheddable in this fashion.

    .
    “The effects of third cousin marriage are probably unnoticeable. Even 2nd cousin doesn’t cause too much trouble. The key number is the autozygosity, the fraction of of the genome that is identical by descent. This drastically increases your chance of having two copies of a deleterious mutation.”

    Among which populations though?

    If you had an ancient valley where 100 or so families have been inter-marrying for a millenia then is it the same? I don’t doubt you know more than me about the details of this but i don’t believe anyone has ever checked and if it’s true that close-cousin marriage *on top of* an ancient valley effect compounds the issue then i think it’s likely to be easily provable if you knew where the data was as…

    If it’s true then in pretty much every region of places like India there should be identical (on the surface) populations living in the same region following identical marriage practises but one part lives in a higher population density river valley and a second part live in a slightly more arid valley 20 miles away with a lower local population density and if the idea is correct then those two groups – like the rural / suburban Ansari split hubchik mentioned – should have an IQ gap.

    I don’t doubt you know more about the mechanics of this than me but i don’t believe anyone has ever checked if this “ancient valley” effect exists and if so if it *compounds* the effects of close cousin marriage.

    .
    “Average autozygosity is 1/16 for first cousins, 1/64 for second cousins, 1/256th for third cousins. .”

    For everyone or just WEIRD populations?

    .
    “This article discusses Korea’s tradition against “intra-clan” marriages”

    That’s the standard global form of inbreeding which is kind of a halfway house between the western model and FBD. I suspect it’s standard because it’s so simple. The men keep the clan surname and the rule is same-surname marriage is against the rules. If you think about it what it means is you stop close marriages along the male line only i.e. you can’t marry your uncle’s kids but you can marry your aunt’s kids. The western model was a ban along *both* lines.

    Reply

  30. “Here the Ushijima intelligence test was administered to 1365 children in 1953 and to a comparable sample of 1370 children in 1960 with the objective of determining any change in the mean over this relatively short period. The children were aged 9-15 years.

    “(i) All age groups show a rise in scores for all abilities. The overall mean increase was 0.66 standard deviations, the equivalent of 9.9 IQ points, and representing an IQ gain of 14.1 IQ points per decade.”

    The children tested would have been born in roughly 1940 and 1950.

    According to the graphs above, consanguineous marriages were around 17% in 1940, and around 10% in 1950.

    So if it was due to a decline in consanguineous marriage, then that would mean that a 7% decline in consanguineous marriage raised the overall mean IQ in a population where the majority of marriages aren’t consanguineous by 1 standard deviation in a decade. To change the overall mean by 1 SD, the change in IQ among 7% would have to have been much higher. That is, 7% of marriages that were previously producing moronic children were 10 years later producing very smart ones. That seems unlikely.

    Most likely it was due to children being born during wartime. Japan invaded China in 1937. The oldest children tested in 1953 would have been born in 1938, and the youngest would have been born in 1944.

    [edit: sorry – your other comments went into the spam box. no idea why. – h.chick]

    Reply

  31. @gtca – “So if it was due to a decline in consanguineous marriage, then that would mean that a 7% decline in consanguineous marriage raised the overall mean IQ in a population where the majority of marriages aren’t consanguineous by 1 standard deviation in a decade. To change the overall mean by 1 SD, the change in IQ among 7% would have to have been much higher. That is, 7% of marriages that were previously producing moronic children were 10 years later producing very smart ones. That seems unlikely.”

    yes, does seem unlikely. however, like cochran said above, that the japanese quit marrying their cousins may (may) have added a few iq points, just maybe not so many.

    as a side note, one shouldn’t rely fully on just one or two sets of data on consanguineous marriages for a population. it’s been my experience that there can be quite different results from different surveys. for instance, i came across another study which reported a 50% consang rate for japan for this same time period. i’ll post it — or post a link to it — as soon as i figure out where i put it! (~_^)

    Reply

  32. “That is, 7% of marriages that were previously producing moronic children were 10 years later producing very smart ones. That seems unlikely.”

    It does seem unlikely and probably is unless there’s an ancient valley effect from small populations intermarrying for centuries.

    If my understanding is correct – and maybe it isn’t – i think it depends on the premise of what an advantageous allele is. *If* evolution doesn’t select for IQ unless it has to but instead selects for the minimum average IQ necessary for a group to survive in their environment – balancing energy costs and skull size with diminishing returns on higher IQ for simple tasks like shepherding – then wouldn’t alleles that reduce average IQ (down to the sweet spot for the environment) be advantageous?

    And if they were advantageous couldn’t they sweep through a small enclosed population quite fast? And dissappear quite fast also?

    .
    “where the majority of marriages aren’t consanguineous”

    Again, is there (or was there) a WEIRD version of non-consanguinous and a non-WEIRD version where the most recent marriage may not have been technically consanguinous but still with someone from among 100 or so families that had been inter-marrying for centuries?

    Reply

  33. At what point does a population become ‘out-bred’? For example, if a population is very small and very isolated with little or no genetic input since its founding then presumably whether or not members consciously choose to marry cousins or not they will likely be doing so anyway. I am thinking of Andaman Islanders, isolated Amazonian tribes, etc etc.

    Reply

    1. @ chrisdavies09 “population is very small and very isolated with little or no genetic input since its founding then presumably whether or not members consciously choose to marry cousins or not they will likely be doing so anyway.” There is data on that, including Long House Valley, Japanese and Chinese dynasties and the bureaucrat class of most of the civilizations I have decent numbers on, as contrasted with tiny villages (as in England, although as we have learned they were not exclusive and hunter gatherers. The bottom line seems to be that it depends on how large that popualtion is permitted to grow. If numbers are restricted to, oh, a hundred I would guess (that’s reproductive adults, not everybody) then it appears they the population is virtually immortal. If the population grows to a thousand, then you can expect them to die out from oubreeding in three hundred years.
      Don’t bet the farm on that. It’s just the best I can do with what I have found. Of course you can overdo inbreeding, just as you can overdo outbreeding. I have been amazed at how little freedom biology gives us in the long run.

      If somebody had told me this fifteen years ago I would simply have snorted and shrugged.

      Reply

  34. chrisdavies
    “At what point does a population become ‘out-bred’?”

    I’m not sure there is a fixed definition as it’s really a relative term – more outbred than and more inbred than. I expect it would be possible to fix a definition but i’m thinking it would take knowing for sure whether there was *compund* inbreeding – for want of a better term.

    .
    “For example, if a population is very small and very isolated with little or no genetic input since its founding then presumably whether or not members consciously choose to marry cousins or not they will likely be doing so anyway.”

    Yes. This is very relevant to how far the basic idea extends. Does a situation like you describe – even if the population are trying to minimize the closest marriages – create an inbreeding effect separate from the well-known effect of deliberate close-cousin marriages.

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  35. @Linton “I have been amazed at how little freedom biology gives us in the long run.”

    That’s a classic! btw I have looked on your site (loved the piece about Goya, what a painting, almost cubist) but I haven’t been able to find a summary of your hypothesis or any tables of data – I’m interested in TFRs, projections for countries sort of thing. I also couldn’t see how to comment even though I went t’ Chat page, so apols HBDC for using this blog to inquire.

    Reply

    1. @Big Nose Kate “I haven’t been able to find a summary of your hypothesis or any tables of data ” I had kind of noticed that year after year I never got any comments on that chat page. Here’s the link for the summary.

      http://nobabies.net/A%20December%20summary.html

      If that doesn’t work, drop me a note at info@nobabies.net and we’ll figure out what will work. Guess I need to take that invitation to the non functioning chat room down.
      thanks.

      All Total Fertility Rate projections I have seen are based on the assumption “Assuming all the women in the country continue to have children at the same rate at every age as they are having now.” Since that has never been true in past couple of generations I find it of limited use going forward.

      Reply

  36. Hi Linton, I found that v. interesting reading. Your concluding graph looks like a coiled serpent! ………But have I understood?
    Is the final graph based on 3 scales, with Time being the reason why the line curves back and forth? Are all populations somewhere on that line?
    Are you saying that there are natural laws (if so, are they Newtonian or Quantum?) that govern the lifespan of a ‘community’, and that those laws _enable_ speciation to operate as a process?
    Is evolution simply a set of feedback loops? Is evolution ‘digital’ / algorithmic? (I’m into territory that I don’t understand when it comes to algorithms), and are feedback loops arrived at by simple forces of attraction and repulsion between chemicals, as with the sperm grouping? Are the same forces that govern birth and death of stars/galaxies etc. at work on bio-populations?
    I’m sure you’ll suggest I email you only I can’t at the moment, but even just Yes and No answers would help me.

    Reply

    1. @big nose kate “Your concluding graph looks like a coiled serpent! ………But have I understood? Is the final graph based on 3 scales, with Time being the reason why the line curves back and forth? Are all populations somewhere on that line?”
      Thanks for looking at my effort. I am a bit reluctant to impose on hbd chick as you are. Let me have a go at that first two questions, though.
      Yes, it looks like a snake. The circles in the graph each represent a single year. The size of each circle represents the size of the population of Sweden that year. The head of the snake is the last year for which they have data. In that year age at first marriage was higher than it had ever been before and it had been rising for several years.
      The tip of the tail of the snake is a year I chose in order to clean up the graph. Birth rate and age at first marriage to vary from year to year. What I wanted to show is that from the first year (tip of tail) birth rate falls below replacement (about 2 per woman) and then stops falling, goes up and down (back and forth on the graph) but neither recovers nor continues to zero. This is a pattern almost all countries are following although at different stage. It is only meta stable. You can’t push the age at first marriage up forever without eventually having the birth rate collapse.
      I think it would be better to look at it on gapminder.com, but I find their print very hard to read these days. It used to be easier.
      Hope I havn’t bored the rest of y’all. I’ll be thinking about the third question. Maybe I should put the complete set of answers up on nobabies.net. May I use your questions for that?

      Reply

  37. @ Big Nose Kate “But have I understood?” Thank you again for permission to use your questions. I shall be putting them and my response up on nobabies.net the morning.

    Reply

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