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
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