mother’s brother’s daughter marriage

so, i found out that mother’s brother’s daughter (matrilateral cross cousin) marriage is, apparently, the most common form of cousin marriage globally.

i looked at father’s brother’s daughter marriage before, and noted one interesting feature in which ego’s paternal uncle (his father’s brother) got to pass his y-chromosome on to his daughter’s male children when she married her paternal cousin (because ego shares his paternal uncle’s y-chromosome). this is something a man wouldn’t normally be able to do (since his daughters don’t inherit his y-chromosome). so, fbd marriage is a really good deal for the paternal uncle.

what happens in mother’s brother’s daughter (mbd) marriage?

well, first of all, the y-chromosome doesn’t really matter here because ego doesn’t share a y-chromosome with any of his maternal relatives (unless everyone’s really inbred!).

in the case of x-chromosomes, ego inherits just one x-chromosome from his mother — an x that is a recombination of her two x-chromosomes. so, let’s track her two x-chromosomes.

in the case of ego’s mom’s maternal x-chromosome (i.e. the one she inherited from her mom), ego’s mother’s brother shares an x-chromosome similar, but not identical, to the one that ego’s mom has. (each of them inherited a recombined x-chromosome from their mother.) he passes an (almost) intact copy on to his daughter (the mbd), while ego gets part of his mom’s maternal x-chromosome recombined. the result looks like this (click on images for LARGER versions):

so there’s a few bonuses for several individuals here:

– some of ego’s x-chromosomal dna passes on to ego’s son via ego’s wife (the mbd) — normally a male doesn’t pass any x-chromosomal dna onto his sons;
– ego’s daughters get an extra amount of his x-chromosomal dna via their mother — another way of looking at it is that the mbd gets to pass on an extra amount of her x-chromosomal dna via ego;
– both ego’s mom and his maternal uncle get extra amounts of their x-chromosomal dna in their female grandchildren, and ego’s mom gets to pass some of her x-chromsomal dna on to her son’s male children, something she normally wouldn’t have been able to do.

ok. so that was one of ego’s mom’s x-chromosomes. what about the other one? the other one she inherited from her father, so she doesn’t share it with her brother. so it looks like this:

not very exiciting.

buuuuuut, what if ego’s dad had also married his mbd? that’s how they do it, ya know.

then it would look like this:

as you can see, ego’s father would also get to contribute some of his x-chromosomal dna to his female grandchildren’s genomes (via ego’s mother), something he wouldn’t have done otherwise.

so, that’s a short summary of what happens with the x- and y-chromosomal dna in mother’s brother’s daughter marriage. let me know if you see anything else of interest — or if you see an error in something i wrote here (i am experiencing a bit of a cupcake-induced brain fog after today’s festivities (~_^) ).

previously: father’s brother’s daughter marriage and coefficients of relationship – cousin marriage – grandparents

(note: comments do not require an email. or a family tree.)

13 Comments

  1. From

    http://home.cc.umanitoba.ca/~anthrop/tutor/marriage/matxcuz.html

    “Where a system of bilateral cross cousin marriage results in exchange and alliances between paired lineages, matrilateral cross cousin marriage can unite any given number of lineages in a continuous pattern of circular exchanges.”

    A system pretty much tailor-made for gradually extending the number of clans tied together as part of a larger group. You can picture two neolithic clans on each side of a river valley constantly fighting at the river line and Uggalug Aquinas coming up with an idea like this. By circulating the women around the two clans the group becomes more exogamous at the clan and more endogamous at the mini-tribe level. This group could then go bully a third clan down-river into joining their gang by simply adding the third clan into the rotation.

    nb you could circulate the males instead but then you place more aggressive males among people they are not related to and hence have less genetic restraint towards.

    nb You hear of arranged marriages where the new bride is badly picked on at her new home by the women of her husband’s family. Coming up over the last 30 years in the west your first thought on that might be a feminist-influenced one but obviously if you look at it in a blood is thicker than water way then the real answer is obvious.

    Reply

  2. I was thinking how you could test the band of brothers theory re FBD marriage.

    Take 8 sets of brothers, 1 set each from 2 different nations at 4 different levels of national endogamy

    e.g.
    exogamous: English brothers, German brothers
    hybrid: Italian brothers, Greek brothers
    endogamous (non-fbd): South Indian brothers, somewhere similar
    endogamous (fbd): Algerian brothers, Iraqi brothers

    Experiment
    1) Each pair of brothers goes into a room where after a bit they get spooked, noises lights, roars, gunshots, whatever – presented with a sudden potential threat.

    2) The pairs are swapped so an English is paired with a German and Italian with a Greek etc. So they’re paired in terms of national endogamy but not brothers.

    (I don’t actually know if those nations do have the same levels of endogamy they’re just examples.)

    (You may need more sets of brothers as if you use the same ones in (2) who were in (1) then they won’t be spooked by the sudden noises.

    Anyway what you’d be looking for is the reaction and that reaction would be measured by which pairs moved the most back-to-back and which moved so the most so they were facing each other.

    What i think you’d see is in the first experiment all the brothers would move towards back-to-back but possibly the more so the more endogamous and possibly the more so with FBD over non-FBD. The level of stress might follow the pattern also with the more endogamous more certain of their brother’s reaction and less stressed.

    I think the pattern would be reversed in the second experiment. The more endogamous on a national level pairs would be more inclined to go face-to-face when suddenly spooked while the most nationally exogamous would be more inclined to be 50/50, half facing outward and half watching each other.

    Actually it might be better to have a set of German brothers and a set of German non-brothers, a set of Italian brothers and non-brothers etc.

    But anyway you probably get the idea.

    Reply

  3. Another thought i had about testing some of this was how you could prove genetic level restraint i.e. blood is thicker than water implict restraint.

    I think if you have two very violent brothers and one of them, if he stabbed a stranger, he’d drive it in to the hilt but the same man stabbing his brother would pull it at the last moment so it only went in a couple of inches.

    If it was possible to obtain stabbing info from an ER and collate severity of stabbing with relatedness i think that’s what you’d see (blood relatdness obv.).

    Reply

  4. @g.w. – “A system pretty much tailor-made for gradually extending the number of clans tied together as part of a larger group.”

    yes! i’m pretty sure this form of cousin marriage is, traditionally, the common one in east asia, esp. southeast asia. so, then you get peoples who are tied to one another, but not crazy tribalistic like the arabs.

    i have to sit down one day and map these marriage patterns out — i need to see to get a better grasp of it all.

    Reply

  5. @g.w. – “I think if you have two very violent brothers and one of them, if he stabbed a stranger, he’d drive it in to the hilt but the same man stabbing his brother would pull it at the last moment so it only went in a couple of inches.

    “If it was possible to obtain stabbing info from an ER and collate severity of stabbing with relatedness i think that’s what you’d see (blood relatdness obv.).”

    i think that could very well be right.

    earlier this year, i had a couple of posts up about the cinderella effect — you know, step-parents not being as kind to their step-kids as real parents.

    i never posted about it (it was too depressing for even hbd chick to think about too much), but i (partially) read a research article about how in child homicides, actual biological parents typically kill their kids (when they do) in a pretty quick, painless manner, whereas if a step-parent kills his step-kid, it’s often in a pretty horrific manner, really beating the kid to death kinda slowly.

    relatedness matters — even in the darkest sort-of incidents.

    Reply

  6. Saddam Hussein broke the mold and married his MBD cousin, not FBD according to Wiki. http://en.wikipedia.org/wiki/Saddam_Hussein

    2 of his daughters married Saddam’s 2nd cousins, presumably on his fathers side as he had no nephews afaik .

    He disposed of the 2 sons in law on their return from Jordan, in a particularly Machiavellian fashion even for him.

    One wonders if he might have been more forgiving if the sons in law had been his nephews (as per custom) instead of 2nd cousins?

    Reply

  7. @svk – oh, interesting! i didn’t know. yes, it might’ve been tougher to get rid of nephews as opposed to second cousins. second cousins are a lot more distant.

    gaddafi went for an interesting tactic in marrying his second wife (the one with whom he’s had most of his kids, dunno what ever happened to his first wife). his second wife is from another tribe, not the gaddafi tribe but the al-barasa tribe, apparently a pretty powerful tribe in libya.

    presumably he was trying to forge an alliance with the barasas. they are from the eastern side of the country, the region that is rebelling against his regime. i don’t know if the barasa tribe is supporting gaddafi or not, but the alliance obviously hasn’t helped him in the east.

    Reply

  8. What would happen in these situations if there weren’t enough offspring of one particular sex, and too much of another?

    Also, doesn’t cousin marriage heighten the likelihood of Down’s Syndrome occurring?

    Finally, if cousin marriage was previously the norm, then why does everyone critisize the Appalachian inbreeds?

    Reply

  9. @rhmendelson – “What would happen in these situations if there weren’t enough offspring of one particular sex, and too much of another?”

    well, that’s one of the big questions, isn’t it. like the “bare branches” problem that the chinese talk about. if young men (esp.) can’t find a bride, they might get kinda annoyed — and if you have LOTS of them, you might have problems.

    there are some theories out there that cousin marriage rates increase when the total population numbers increase because there are simply more cousins to marry. not sure i buy that.

    @rhmendelson – “Also, doesn’t cousin marriage heighten the likelihood of Down’s Syndrome occurring?”

    don’t think so. that’s an age-related thing mainly (age of mother). but certainly you can run in to all sorts of inbreeding problems with too much cousin marriage. that’s why there’s so much research done on cousin marriage in places like saudi arabia — they have LOTS of cousin marriage and quite a lot of congenital problems related to all the inbreeding.

    @rhmendelson – “Finally, if cousin marriage was previously the norm, then why does everyone critisize the Appalachian inbreeds?”

    well, i guess because it is not the norm nowadays and people generally don’t know anything about history. (^_^)

    Reply

  10. a Question,if you are married to your daughters partners uncle,and they marry,what is the legal term of this.There is no blood line between my husband and my daughter,he is a step parent only.

    Reply

  11. @arola – “if you are married to your daughters partners uncle, and they marry, what is the legal term of this.There is no blood line between my husband and my daughter, he is a step parent only.”

    heh! (^_^) well, you’re all just in-laws, i suppose. there aren’t any special terms for your situation, as far as i know.

    you are your daughter’s husband’s mother-in-law but also aunt through marriage — but, like you say, not a blood-related aunt. and he is your son-in-law and nephew via marriage.

    and your husband is your daughter’s stepfather and uncle-in-law. she is his stepdaughter and niece-in law. (^_^)

    a bit complicated, but not a problem! (^_^)

    although, if your husband didn’t raise your daughter at all — if you married him when she was older — i, personally, feel weird about calling him her stepfather then. i guess he is, but my mom remarried when i was older, and i never referred to her husband as my stepfather as that seemed weird — just my mom’s husband. or just by his name, obviously. (^_^)

    Reply

    1. thankyou for that,i needed to know because my daughter is in a relationship,and her partner is the nephew of a close friend of mine who has come back into my life.His wife died 8 years ago,she was my best friend,we grew up together.She moved away and had children.We kept in touch and were close,but over the last 10 years drifted apart.I have been reunited with her husband through my daughter and her partner,i wasnt aware that her partners mother was my friends sister.Confused,yes i am.Anyway since being in touch with my friend we have had a conection,its quite strange,but warming,and we have been talking about dating,i thought i would speak to my daughter and she was not happy about it because of the relationship cloud.I just need to know im not stepping into bad waters,and doing anything wrong.Sometimes things just happen.

      Reply

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s