when in rome?

(note: i’ll post the punch line to the do you think like a westerner? post tomorrow…or maybe tuesday. (^_^) )

further to my notion that various jewish populations have tended to imitate the mating patterns (eg. cousin marriage or not) of the broader societies in which they have been situated — at least over the last millennium or so (dunno about the ancient hebrews) — here are some numbers on the types of cousin marriage found in the iranian jewish population. remember that consanguineous marriage is quite high among iranian jews — something on the order of 25%. from Outcaste: Jewish Life in Southern Iran [pg. 112]:

jews - iran- cousin marriage types

notice that nearly one third (3.06%) of all the first cousin marriages (9.88%) are to the father’s brother’s daughter (fbd or FaBrDa in the table). another 1.41% of the marriages are to other patrilateral parallel cousins, probably paternal second cousins. (that’d be father’s father’s brother’s son’s daughter marriage, if you must know. =P or ffbsd marriage! never mind. don’t think about it too hard.)

so ca. 4.5% of iranian jewish marriages are to a patrilateral parallel cousin to some sort. remember that patrilateral parallel cousin marriage (fbd marriage…or ffbsd marriage!) is very unusual. most of humanity avoids it. the vast majority of populations that practice cousin marriage practice maternal cousin marriage — usually cross-cousin maternal marriage or mbd marriage. it’s only the arabized world which favors parallel paternal cousin marriage (and the tswana). it’d be too much of coincidence, i think, for iranian jews to have invented fbd marriage all on their own — i’m betting they picked it up from other iranian peoples after the arabs introduced it to the region.

uuunnnnleeesssss…the jews (also?) introduced it to the region, as they are thought to have done in arabia. hmmmm…?

interestingly, persian jews seem to have put their own twist onto parallel cousin marriage and that is that they also marry maternal parallel cousins (mother’s sister’s daughter or msd marriage or MoSiDa in the table). that form of parallel cousin marriage is even more unusual than fbd marriage. i don’t know of any population that does it. nearly everyone on the planet avoids it. it might, however, have seemed natural to this group of jews — natural, that is, if you’re thinking of adopting parallel cousin marriage at all — since jews have had a very long tradition of allowing/practicing maternal uncle-niece marriage. there are more than two times the number of maternal uncle-niece marriage (SiDa) than paternal uncle-niece marriage (BrDa) in this persian group, for instance. (all of this harkens back to the idea that you know who an individual’s mother is, but you can never be sure who the father is.) i think this is another indicator that persian jews picked up the idea of parallel cousin marriage from the surrounding population (although perhaps it was back in the levant?), and then they adapted it to their own practices. could be wrong. Further Research is RequiredTM.

if (IF) i’m right — going by this persian evidence and the medieval german jewish evidence — that jews have generally adopted the mating patterns of their host populations, then an interesting question is, do other subgroups do this, too? will, for instance, muslim immigrants to the west adopt outbreeding? dunno. mixed signals here. in britain, where most pakistanis are from the kashmir and punjab regions, the total cousin marriage rate in the 1980s (that’s first and second cousins) was 67% [pg. 10]. the rate for all-punjab back in pakistan was 50.3% [pg. 16]. that certainly looks like an increase in cousin marriage in the immigrant population. however, meanwhile in norway, two studies found that pakistani-born pakistanis had higher rates of cousin marriage than norwegian-born pakistanis (37.5% & 34.7% versus 30.1% & 27.1% – pg. 11 – don’t know where pakistanis in norway are from). that looks like a decrease. all things considered, it’s probably too early to tell what the trend(s) might turn out to be.

korotayev and other russian anthropologists have argued — convincingly, imho — that father’s brother’s daughter’s (fbd) marriage was spread by the arabs, since its maximum range today (looking away from the outlier tswana in southern africa) corresponds to the eighth-century caliphate. they further argue that, as part of a more general “arabization” process, the conquered populations emulated their conquerors in all sorts of ways, both in order to succeed in this newly constructed society and, quite possibly, since they viewed the arabs’ culture as somehow superior to their own. the arabs were the conquerors, after all. they must’ve been doing something right! the arabs may even have impressed upon their new subjects that their culture was, indeed, the better one. if they’re right, it seems much less likely to me that immigrant groups to the west will copy our mating patterns if we don’t impress on them that we think they’re important and the right way to go.

previously: historic mating patterns of ashkenazi jews and jewish inbreeding and father’s brother’s daughter’s marriage

(note: comments do not require an email. persian jewish girl. (^_^) )

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the canonical family tree

following up on a reader request, here is an extended family tree for ya with names (boy, it's HARD to pick names for kids!).

everything is from the point-of-view of “jack” (ego). i went for double-barrelled names in order to give some sort of hint as to any given individual’s relationship to jack. so, his father’s brother (his paternal uncle) is “frank bob.” and his father’s brother’s daughter (his paternal first-cousin) is “frances betty” (see what i did there?).

here they all are (click on charts for LARGER images – should open in new tab/window):

now, in father’s brother’s daughter marriage (i can see your eyes glazing over already!), jack marries his uncle frank’s daughter, cousin frances. in a society where this is a common practice (eg. arab world), they do this over and over again, although maybe not in every generation. if it were every generation, it would look like this:

so, all of the jacks marry their cousins frances betty. see how the lineage keeps folding back in on itself? this is some close inbreeding.

also, see the left side of the canonical family tree? — where uncle mike and aunt martha are? mom’s brother and sister? that side of the family tree doesn’t really exist in an fbd system, ’cause mom’s brothers and sisters are ALSO dad’s paternal cousins. in an fbd system, the left side of the family tree should really be over on the right side. (*facepalm*) maybe i’ll try to draw that one day. it’s no wonder that most peoples in the world consider fbd marriage to be too incestuous — interesting that most people figured that out and avoid it.

now, here’s mother’s brother’s daughter marriage, the most common variant of cousin marriage and the most common form found (traditionally) in china:

again, all of the jacks marry their mother’s brother’s daughter (mbd) — mary beth. but this time, dad is NOT related to mom’s side of the family via his patrilineage. this is a sort-of inbreeding, but not so close as fbd marriage above. not always within the same lineage. mom’s brother, mike, is probably married to a woman from some other lineage, so cousin mary beth is not so closely related to jack. dad’s brother, frank, on the other hand, is probably also married to a woman from the patrilineage, so (in fbd marriage) jack and frances betty are probably more closely genetically related.

what the canonical family tree needs, really, are surnames. (why didn’t i think of that sooner?!)

imagine the fbd marriage system above — jack’s new wife, cousin frances betty, doesn’t have to change her last name ’cause she’s in the same patrilineage as jack. jack smith, let’s say, marries his father’s brother’s daughter — uncle frank bob smith’s daughter, cousin frances betty smith. see?

in the mbd marriage system, on the other hand, jack smith marries his mother’s brother’s daughter — uncle mike bill jones’ daughter, cousin mary beth jones. mary beth needs to change her name ’cause she’s from another patrilineage. like confucius say marriage is “the union of two surnames, in friendship and in love.”

previously: genealogical terminology

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

cousin marriage rates in modern china

surveys of late-twentieth century cousin marriage rates in urban china — places like beijing and shanghai — have found very modern marriage patterns, i.e. very low consanguinity rates (0.7% – 0.8% of all marriages between 1949-67 in those two cities being between first- and second-cousins).

rural areas, otoh, have remained more inbred — rural hubei province having rates between 2.8% – 4.3% between 1949-67.

zhaoxiong found that just the first-cousin marriage rate in lijiawan village in hubei between 1949-93 (note that cousin marriage in china has been technically illegal since 1980) was 8.4%. that’s quite a bit higher than the rates above, especially considering that it doesn’t include second-cousin marriages (the rates above do — who knows how many second-cousin marriages there were in lijiawan?).

zhaoxiong also found that mother’s brother’s daughter (mbd) marriage was the most common form, followed by mother’s sister’s daughter (mzd) and, then, father’s sister’s daughter (fzd). nobody married their father’s brother’s daughter (fbd).

as wang, et. al., point out: “[T]here is a long history of consanguineous marriage in China….” however, cousin marriage rates in china have been dropping since at least the middle of the twentieth century — but they’re still pretty high in rural communities.

the genetic ties are starting to loosen in china. if they keep it up, that could prove to be a good thing in terms of having a more cohesive rather than a clannish society. don’t ask me how many generations they’ll need to make this happen! wish i could be around in a few hundred years to see how it worked out for them. (^_^)

many thanks to m.g. for the zhaoxiong article! (^_^)

previously: cousin marriage in china and abridged history of cousin marriage in china and china today… and china and landlordism and what else happened during the middle ages?

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cousin marriage in china

from “Rethinking cousin marriage in rural China”:

“This article considers cousin marriage rules among affines in rural Chinese culture, based on research in Hubei Province….

“Studies during the last several decades have proposed different explanations of cousin marriage among Chinese, but none provides an accurate and comprehensive principle to explain the rules that guide the selection of marriage partners among relatives in rural Chinese society….

“For the Chinese, qinqi (affines) are relationships created through marriage, and are sharply distinguished from members of one’s own lineage. In the kinship terminology, patrilateral parallel cousins are tang (FBS and FBD), but all patrilateral cross-cousins, matrilateral cross-cousins, and matrilateral parallel cousins are biao (remote) relatives for Ego, male or female.

“Marriage within the lineage, especially FBD marriage [father’s brother’s daughter marriage], is treated like marriage between kin and tantamount to sibling marriage. Because this type of marriage is strictly forbidden, both in custom and in law, it does not need attention here. (2) But marriages between other types of first cousins are regarded quite differently. FZD [father’s sister’s daughter marriage], MBD [mother’s brother’s daughter marriage], and MZD marriages [mother’s sister’s daughter marriage] for a male ego have usually been referred to as biao or zhong-biao (outside) marriages. Although the marriage rules that prevailed during the dynastic era of China’s history generally tolerated such marriages (Li 1950:99-100), they have been prohibited for genetic reasons in both mainland China and Taiwan since the 1980s (Tao, Wang, and Ge 1988:313; Liang 1995:14). In practice, however, this type of marriage continues in a great many villages (Wu, Yang, and Wang 1990:330).

Previous research indicates considerable regional variation in attitudes and preferences related to biao marriages. For example, in both Kaixiangong Village in Jiangsu Province, where Fei (1939) did fieldwork, and Phoenix Village in Guangdong Province, which Kulp (1925) studied, MBD marriage was preferred and FZD marriage frowned upon (Fei 1939:50-51; Kulp 1925:168). According to Hsu (1945:91), the people of West Town in Yunnan Province favored MBD marriage, tolerated MZD marriage, but disapproved of FZD marriage. On the basis of his fieldwork and that of Fei and Kulp, Hsu (1945:100) makes the generalization that MBD marriage is preferred all over China, whereas in most regions FZD marriage is not….

Controversy remains, however, as to whether among cousin marriages MBD marriage is preferred in every region of China. Freedman (1958:98-99), for example, contends that MBD marriage is not prevalent everywhere in China and certainly not in southeast China. Gallin (1963), based on his research in a Taiwanese village, considers that in China MZD marriage is not considered particularly problematic, and that MBD marriage is preferred over FZD marriage. Furthermore, MBD marriages are not favored so much as simply permitted, and FZD marriages tend to meet with disapproval more often than with tolerance. Gallin (1963:108) suggests that in some regions MBD marriages may be actively preferred, but in general they are merely considered acceptable.”

so historically — which is a loooong time in china — cousin marriage was very much a part of chinese marriage practices. but it sounds like the types and frequencies varied between regions — and prolly over time, too. china’s a big place, after all.

that’s why i questioned kirin, et. al.’s statement:

“This is not surprising because both of these groups [europeans and east asians] are mainly represented here by fairly large populations with no documented preference for consanguineous marriage.”

if they mean now — well, yessort-of. if they mean at all historically — and by that i mean anytime before the mid-twentieth century — then, no. that’s just not right.

i don’t have acess to the above article, but i’m gonna order it, so i’ll post more about chinese cousin marriage sometime soon(-ish). (^_^)

previously: china today… and what else happened during the middle ages? and china and landlordism and chinese kinship terms…

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rough guide to inbreeding and outbreeding

this is obviously an over-simplification, but i wanted to outline some of the effects that inbreeding and outbreeding have on social behaviors. so, it’s way, waaaay over-simplified. it’s just me thinking out loud.

these are just a few of my favorite things i thought of off the top of my head. there’ve been many others discussed around here lately — like harmonious jim suggested that exogamy lead to humanism. i think that’s prolly pretty right. we wouldn’t have gotten here without strong exogamy anyway.

also, there ought to be more gradations here, but i didn’t bother right now — like somewhere in between “no inbreeding” (nuclear families) and “maternal-side inbreeding” (clans) there ought to be extended families — not completely outbred, but not as inbred as clan-based societies. (maternal-side inbreeding = mbd & mzd marriage; paternal-side inbreeding = fbd & fzd marriage.)

anyway — here is a rough guide to some of the apparent effects of inbreeding and outbreeding on social behaviors. do, please, suggest some more! (and/or take issue with these!):

(note: comments do not require an email. medieval squirrel.)

tribes and types of cousin marriages ii

in the previous post on tribes and types of cousin marriages, i posted a couple of graphics illustrating father’s brother’s daughter (fbd) marriage and mother’s brother’s daughter (mbd) marriage, showing how fbd marriage is a closed system while mbd marriage enables alliances with other lineages/clans.

here now are the last two forms of cousin marriage: father’s sister’s daughter (fzd) marriage and mother’s sister’s daughter (mzd) marriage. they’re not very different from the other two — fbd and fzd marriage are both closed systems, and mbd and mzd marriage both enable alliances with other lineages/clans — it’s just that the connections are slightly different, i.e. ego marries the daughter of his one of his aunts (fzd & mzd) versus his one of his uncles (fbd & mbd).

note that the coefficients of relatedness in cousin marriage are highest for mzd marriage; next highest for mbd marriage; and lowest for both fbd and fzd, which are the same (if i’ve done my maths right!). mbd marriage is the most common form of cousin marriage around the world; fbd marriage is the most common in arab countries and places like iran, afghanistan and pakistan.

here we go. father’s sister’s daughter (fzd) marriage over several generations (triangles are boys, circles are girls. compare with fbd marriage):

and mother’s sister’s daughter (mzd) marriage over several generations (compare with mbd marriage):

the thing with either mbd or mzd marriage is that the bride is always being brought in from an outside lineage or clan. fbd and fzd marriage is diametrically the opposite — the bride is from the same patrilineage as ego.

also, in mbd and mzd marriage, in each generation a bride can be brought in from a different lineage or clan, so ego’s lineage can build up many alliances with many other lineages/clans over time. some societies apparently have, traditionally, had arrangements in which several lineages would swap brides over several generations in a cyclical system, thus building up extended familial connections and, therefore, alliances. i imagine that very large tribes could be built up this way, whereas the fbd/fzd system results in segmented lineages, i.e. clans and sub-clans and sub-sub-clans that always seem to be squabbling.

previously: tribes and types of cousin-marriage and genealogical terminology and what is a tribe?

(note: comments do not require an email. happy hour, anybody? (^_^) )

coefficients of relationship – cousin marriage – grandparents

ok. back to business.

last time i regaled you with my new-and-improved coefficients of relationship/relatedness for the nuclear family members in all forms of cousin marriage (from the p.o.v. of a guy) — MBD (mother’s brother’s daughter) marriage, MZD (mother’s sister’s daughter) marriage, FBD (father’s brother’s daughter) marriage, and FZD (father’s sister’s daughter) marriage. (here’s a key to all the terms if you want to follow along. i also had neat diagrams of the four forms of cousin marriage in the previous post just in case, like me, you’re a visual sort-of person.).

now i’ve added the brothers & sisters as well as the grandparents. here we go (click on chart for LARGER image):

again, all of the family members (probably) share the most dna (i.e. alleles) in MZD marriage, and (ignoring the “no inbreeding at all” category) they share the least in FBD and FZD marriage. from what i’ve read, maternal cousin marriage is the most common globally (not in the middle east, tho), but i’m not sure which one — i.e. if it’s MBD or MZD. i’ll get back to you on that one. (see update below.)

to just repeat exactly what i said in the previous post (’cause i’m too lazy to write up something new and exciting):

the calculations are based on the fact that there is differential x- and y-chromosome inheritance from fathers and mothers to sons and daughters. this seems to matter in an inclusive fitness sort-of way between grandmothers and their grandchildren, so why not between all the other members of the family?

throw inbreeding into the mix, and you wind up with the members of some families being more related to one another than members of other families depending on the type of inbreeding (see chart).

here’s a couple of examples of how i did the math. please, tell me if you think my logic is wrong (very possible) and/or my calculations are wrong (very probable!).

first of all, the percentages of autosomal, x- and y-chromosomal dna that men and women have (based on the vega genome browser) are:

Female genome
6068 Mbp
Autosomal DNA: 5758 Mbp (≈94.89%)
X: 155 Mbp (≈2.55%), XX: 310Mb (≈5.11%)

Male genome
5972 Mbp
Autosomal DNA: 5758 Mbp (≈96.42%)
X: 155 Mbp (≈2.60%), Y: 59 Mbp (≈0.99%), XY: 214 Mbp (≈3.58%)

and here, the calculations for the genetic relatedness between paternal grandfather and son (PGF-s) when there is no inbreeding and in the four different types of cousin marriage:

PGF-s (no inbreeding)
**parents share no dna.
1/4 autosome + y-chromosome = (96.42% x 0.25) + 0.99% = 0.2510

PGF-s (MBD marriage)
**a man and his MBD share 1/8 of their autosomal dna + 1/4 x-chromosomal dna, so a PGF and a grandchild will share an additional 1/32 of their autosomal dna + 1/16 x-chromosomal dna.
1/4 autosome + 1/32 autosome + 1/16 x-chromosome + y-chromosome = (96.42% x 0.25) + (96.42% x 0.03125) + (2.60% x 0.0625) + 0.99% = 0.2827

PGF-s (MZD marriage)
**a man and his MZD share 1/8 of their autosomal dna + 1/4 x-chromosomal dna + 1/8 x-chromosomal dna, so a PGF and a grandchild will share an additional 1/32 of their autosomal dna + 1/16 x-chromosomal dna + 1/32 x-chromosomal dna.
1/4 autosome + 1/32 autosome + 1/16 x-chromosome + 1/32 x-chromosome + y-chromosome = (96.42% x 0.25) + (96.42% x 0.03125) + (2.60% x 0.0625) + (2.60% x 0.03125) + 0.99% = 0.2835

PGF-s (FBD marriage)
**a man and his FBD share 1/8 of their autosomal dna, so a PGF and a grandchild will share an additional 1/32 of their autosomal dna.
1/4 autosome + 1/32 autosome + y-chromosome = (96.42% x 0.25) + (96.42% x 0.03125) + 0.99% = 0.2811

PGF-s (FZD marriage)
**a man and his FZD share 1/8 of their autosomal dna, so a PGF and a grandchild will share an additional 1/32 of their autosomal dna.
1/4 autosome + 1/32 autosome + y-chromosome = (96.42% x 0.25) + (96.42% x 0.03125) + 0.99% = 0.2811

rinse and repeat for all the other family members.

previously: coefficients of relationship – cousin marriage – nuclear family members

update 07/04: apparently, MBD marriage (matrilateral cross cousin marriage) is the most common form of cousin marriage.

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coefficients of relationship – cousin marriage – nuclear family members

so, here are the coefficients of relationship/relatedness (if i’ve done the maths right) for all the nuclear family members in each type of cousin marriage from the point-of-view of a guy — MBD (mother’s brother’s daughter) marriage, MZD (mother’s sister’s daughter) marriage, FBD (father’s brother’s daughter) marriage, and FZD (father’s sister’s daughter) marriage. (here’s a key to the terms so you can keep track of all the players).

notice that the various nuclear family members (probably) share the most dna (i.e. alleles) in MZD marriage, and they share the least in FBD and FZD marriage. (well, they share the least when there’s no inbreeding, but you know what i mean.)

now, here’s what each of the marriage systems looks like. first, MBD:

MZD:

FBD:

FZD:

the calculations are based on the fact that there is differential x- and y-chromosome inheritance from fathers and mothers to sons and daughters. this seems to matter in an inclusive fitness sort-of way between grandmothers and their grandchildren, so why not between all the other members of the family?

throw inbreeding into the mix, and you wind up with the members of some families being more related to one another than members of other families depending on the inbreeding (see chart at top).

here’s a couple of examples of how i did the math. please, tell me if you think my logic is wrong (very possible) and/or my calculations are wrong (very probable!).

first of all, the percentages of autosomal, x- and y-chromosomal dna that men and women have (based on the vega genome browser) are:

Female genome
6068 Mbp
Autosomal DNA: 5758 Mbp (≈94.89%)
X: 155 Mbp (≈2.55%), XX: 310Mb (≈5.11%)

Male genome
5972 Mbp
Autosomal DNA: 5758 Mbp (≈96.42%)
X: 155 Mbp (≈2.60%), Y: 59 Mbp (≈0.99%), XY: 214 Mbp (≈3.58%)

and here, the calculations for the genetic relatedness between father and son (F-s) when there is no inbreeding and in the four different types of cousin marriage:

F-s (no inbreeding)
**parents share no dna
1/2 autosome + y-chromosome = (96.42% x .5) + 0.99% = 0.4920

F-s (MBD marriage)
**a man and his MBD share 1/8 of their autosomal dna + 1/4 x-chromosomal dna
1/2 autosome + 1/16 autosome + 1/8 x-chromosome + y-chromosome = (96.42% x .5) + (96.42% x 0.0625) + (2.60% x 0.125) + 0.99% = 0.5555

F-s (MZD marriage)
**a man and his MZD share 1/8 of their autosomal dna + 1/4 x-chromosomal dna + 1/8 x-chromosomal dna
1/2 autosome + 1/16 autosome + 1/8 x-chromosome + 1/16 x-chromosome + y-chromosome = (96.42% x .5) + (96.42% x 0.0625) + (2.60% x 0.125) + (2.60% x 0.0625) + 0.99% = 0.5571

F-s (FBD marriage)
**a man and his FBD share 1/8 of their autosomal dna
1/2 autosome + 1/16 autosome + y-chromosome = (96.42% x .5) + (96.42% x 0.0625) + 0.99% = 0.5523

F-s (FZD marriage)
**a man and his FZD share 1/8 of their autosomal dna
1/2 autosome + 1/16 autosome + y-chromosome = (96.42% x .5) + (96.42% x 0.0625) + 0.99% = 0.5523

rinse and repeat for all the other characters.

thnx again to the reluctant apostate for his gallant help! (^_^)

p.s. – of course, there are other family members a guy could marry|mate with — niece, aunt, sister, mother(!), second-cousin, double first-cousin (not uncommon in the arab world), etc. i’ll be gettin’ to those at a later date.

previously: fbd marriage – genetic relatedness amongst nuclear family members and new and improved coefficients of inbreeding and new and improved coefficients of relationship

update 06/08: chart updated ’cause i found a couple of errors in my math (see, i TOLD you!) — with the women (e.g. d-F). should be fixed now. (*hbdchick crosses fingers*)

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