increases in inbreeding in italy after the wars(?)

when i was looking at the numbers for inbreeding in italy last night, i thought i noticed something curious — increases in consanguineous marriages in the years after the two world wars (edit: against a backdrop of a general decrease in inbreeding from 1910 through 1964).

i don’t think i’m imagining it (click on chart for LARGER version):

the chart illustrates the averages of the mean inbreeding coefficients over time (1910-1964) for all the regions in italy which cavalli-sforza, et. al., compiled church dispensation data (the data can be found here). i used data only from the regions which had complete data for all the years.

to me, it looks like there was an increase in consanguineous marriages in the time periods 1920-24 and 1945-49, i.e. post world wars. that’s not what i would’ve expected ’cause you’d think there’d be a shortage of men — including related men — after the wars, so you’d think close relative marriage would go down. yet, it seems like people went out of their way to marry relatives after the wars. maybe this is some sort of crisis response? circle the genetic wagons in (or immediately after) times of distress? i dunno.

(there’s a theory circulating out there these days that the reason that cousin marriage has increased — yes, increased — in arab countries during the past decade or two is because the population has increased so there are more cousins available to marry. if i can find the reference, i’ll share it with you. promise! (edit: see update at end of post.)

sicily is not included in the chart above ’cause, if you read yesterday’s post, you might remember that sicilians don’t have to get church dispensation to marry first-cousins-once-removed (1 1/2C) or second cousins (2C), so i didn’t want to include them with the rest of the italians and screw up the numbers. here’s what the chart for sicily looks like (click on chart for LARGER version) (edit: i updated the sicily chart so that it has the same scale as the italy chart.):

again, it looks like two post-war peaks (edit: and a great depression one?). there also seems to be a greater war-time dip during wwii for sicily. i think, tho, that there might be a more pronounced roller-coastery effect on the sicily chart since the sample number is lower (n=7 verus n=61 for the rest of italy).

it would’ve been interesting to have more data stretching further back in time for italy, ’cause on both the italy and sicily charts, the starting number seems a little lower than the wwi years. what was going on before 1910 in italy?

it would also be cool to have long-term data like this for other countries, including war-time periods. i’d like to know if this is a real phenomenon, or just a figure of my imagination.

oh. here are the numbers (click on the … oh, you know the drill!). italy minus sicily:

sicily:

edit: boilerplate and boilerplate 2.0

previously: inbreeding in italy

update – articles regarding how rates of consanguineous marriages often increase alongside general population increases (or, more specifically, with greater survival rates):

The Prevalence and Correlates of Consanguineous Marriages in Yemen: Similarities and Constrasts with Other Arab Countries
Modernization and Consanguineous Marriage in Iran
The Role and Significance of Consanguinity as a Demographic Variable

another update: see also i wasn’t imagining it

(note: comments do not require an email. la dolce vita!)

9 Comments

  1. I’m not sure I find it incredibly surprising. While there is a shortage of men during wartime and in its immediate aftermath, this would be true generally, not just locally. The factor that war introduces is adversity, both in terms of an enemy to fight and the disorder that in causes, especially in countries such as Italy that had battles on its soil.

    If you remember, there was a study (if I remember properly, it was conducted in the Netherlands) that circulated in mainstream newspapers about how white Europeans would sit closer to a black man at a bus stop when it appeared clean and ordered rather than dirty and disheveled. In times of disorder, people turn inward and the World Wars were definitely times of disorder for Italy, so it would make sense to me that the trend towards greater and greater exogamy would be momentarily reversed at those two moments in Italy’s history.

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  2. @r.a. – “If you remember, there was a study (if I remember properly, it was conducted in the Netherlands) that circulated in mainstream newspapers about how white Europeans would sit closer to a black man at a bus stop when it appeared clean and ordered rather than dirty and disheveled.”

    huh! no, never heard of that study. i’ll have to look it up! makes sense.

    Reply

  3. Interesting observation. Perhaps shortly after the war, it’s harder to find available young men on the streets anyway. So the parents/uncles/aunts of the girl just introduced whoever young men they know of, mostly relatively? It would be interesting to look at the data in Russia, as they suffer greatly from the WWII, I wonder if they have a surge of consanguineous marriages there after the war.

    Btw, checked one of the papers you provided: Yemen: “Among ever-married women under 50 years
    of age, more than one-third (39.9%) reported that they have a blood relationship with
    their husbands” That’s some shocking facts to me… No wonder they couldn’t come up with better idea than Allahu Akbar… just saying

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  4. @the slitty eye – “That’s some shocking facts to me…”

    yes, the cousin-marriage rates in arab countries (and pakistan and afghanistan) are very high. you can get a quick overview of them on this map here, although keep in mind that the map is starting to be a bit dated and is lacking in some nuances here and there. like china, for instance — the cousin marriage rates for china appear to be between 1-4%; but as you and i both know, that’s because the cousin-marriage rates of the hill-tribes and muslims in china are pulling the national score up.

    the arab numbers are really startling, tho. and they’ve been marrying their cousins since before mohammed … so that’s a LOT of inbreeding.

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  5. “the arab numbers are really startling, tho. and they’ve been marrying their cousins since before mohammed … so that’s a LOT of inbreeding.”

    Interesting. That actually reminds me of Yemen, the origin of Arab civilization. The Sabaeans and Axum should be pretty smart people back then, for they have played important roles in connecting the trade between India and the Mediterranean region back then. Yemen seemed used to have a flourishing civilization. Wonder why Arabs end up crazy about marrying cousins in the end….
    On the other hand, I wonder if ancient Jewish had the same habit as well. After all, Yemen back then was under heavy influence of Judaism. Just wondering….

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  6. “That actually reminds me of Yemen, the origin of Arab civilization. The Sabaeans and Axum should be pretty smart people back then,”

    My guess would be they were conquered at some point by the desert pastoralist tribes and that changed them.

    http://en.wikipedia.org/wiki/Marib_Dam

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  7. @the slitty eye – “Wonder why Arabs end up crazy about marrying cousins in the end…. On the other hand, I wonder if ancient Jewish had the same habit as well. After all, Yemen back then was under heavy influence of Judaism. Just wondering….”

    sorry — dunno why this comment of yours slipped under my radar! =/

    the ancient jews (hebrews) absolutely married their cousins on a regular basis — and the common form was the good ol’ fbd marriage. (robin fox talks about the ancient hebrews and their mating practices quite a bit in “The Tribal Imagination.”)

    fbd (father’s brother’s daughter) marriage is thought to have originated in the syro-palestine region since so many different groups there (or from there) practice it. and it’s thought that jews, via their settlements in the arabian peninsula, introduced the concept to the arabs — so you’re right on target with your thinking!

    here’s a couple of paragraphs from this article:

    “At the time of its origin, FBD marriage had nothing to do with Islam. The cognitive problem [i.e. most peoples feel that fbd marriage is VERY incestuous, so the cognitive problem is to overcome this aversion to fbd marriage] solution seems to have occurred somewhere in the Syro-Palestine region well before the birth of Christ. Rodionov (1999) has recently drawn attention to the fact that this marriage pattern is widespread in the non-Islamic cultures of this area (e.g., Maronites or Druze) and that it has considerable functional value in this non-Islamic context in facilitating the division of property among brothers after their father’s death (Rodionov 1999). Like Rodionov (1999), I believe that this marriage pattern could hardly be attributed to Islamic or Arab influence here. It seems, rather, that this marriage pattern in the Islamic world and the non-Islamic Syro-Palestinian cultures stems from the same source.

    “But prior to the time of Islam, the diffusion of the FBD marriage pattern was rather limited. The only adjacent area where it diffused widely was the Arabian Peninsula (Negrja 1981; Kudelin 1994), where its diffusion can be linked with a considerable Jewish influence in the area well before Islam (Crone 1987; Korotayev 1996; Korotayev, Klimenko, and Proussakov 1999). In any case, by the seventh century, preferential parallel-cousin marriage became quite common among several important Arab tribes (Negrja 1981; Kudelin 1994). In the seventh and eighth centuries, an explosive diffusion of this pattern took place when Arab tribes, backed by Islam, spread throughout the whole of the Omayyid Khalifate. Although preferential parallel-cousin marriage diffused (together with Islam and Arabs) later beyond the borders of the Omayyid Khalifate, the extent of this diffusion was very limited. Hence, the present distribution of FBD marriage was essentially created by the Muslim Arab conquests of the seventh and eighth centuries….”

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