structural endogamy

for those of us who prefer to think about things in pictures/drawings/pie charts/hieroglypics rather than numbers (*hbd chick frantically raises her hand in the back of the classroom*), anonymous commenter pointed out this wikipedia page on structural endogamy to me (thanks, anonymous commenter! (^_^) ).

here, at long last, are a bunch of people diagramming mating patterns. ACTUAL mating patterns from real world examples. in detail.

below, for instance, are what the mating patterns — and the resultant connections between the members of the group — in a turkish nomadic clan look like (i haven’t read about this specific example yet, but i’m going to assume that this diagram represents a case of regular preferred father’s brother’s daughter’s [fbd] marriage since that’s pretty common amongst turkish nomadic clans):

structural endogamy - turkish nomad clan

the nodes that you see there, i.e. the colored dots, are married couples, not individuals. as you can see, this is a very tightly related clan with nearly everyone being connected somehow to the two founding couples. there’s a tight “core” to this clan, but it does expand in later generations simply due to the increase in the number of its members.

here’s a more detailed diagram of what i think must be the same turkish clan:

structural endogamy - turkish nomad clan 02

yeah. complicated!

and here’s a different mating pattern altogether mapped out. this is from a mexican village in which anything closer than, and including, marriage to a second cousin was not allowed (sounds like the influence of christianity to me, but i could be wrong about that), however marriage within the village was preferred (the village was studied in the late 1970s and the authors describe it as having been in a transitional phase in between a traditional nahuatl way of life and a more modern mestizo stage):

structural endogamy - belen mexico

as you can see, everyone’s still connected since most people married within the village, but the relationships are not as close as in the more closely inbreeding turkish clan. neat!

i’m sure i’ll be looking further into this structural endogamy or (marital) relinking as it’s also sometimes called. there’s even a whole book on the subject!

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



  1. wow wow wow – keep them pictures coming – something I can understand!

    Proteins are v photogenic too – and vvvvvv diverse!

    How do you like the term ‘anthrogenic’? as in ‘making people’ – is it already in use?

    UK has gone into meltdown – juries don’t understand what ‘evidence’ means anymore


  2. it’s thursday – must be random post day :)

    when i was working in Nepal with farmers I had to learn bits about agriculture. They save seed, and they save a mixture of different landraces so they can sow a diverse range of traits, long, short, wheaty, stalky etc. just wondered if this type of agriculture is well-suited to people who are practicing a similar method with their own genes?


  3. @big nose kate – “it’s thursday – must be random post day :)”

    EVERYday is random post day. (~_^) (noooobody expects the random post….)


  4. “Why didnt outbreeding increase the IQ of mestizos”

    The implication is there’s two parts to IQ, positive genes that were specifically selected for and a bunch of random mildly negative ones aka genetic load. Each population would then have an upper *potential* ceiling depending on which positive selection events they’d had in their history and an actual level which would be their peak *minus* how much load they had. The outbreeding – if it reduced load (or at least some kinds of load if not all) – could therefore only raise the population to their peak not increase the peak per se. Increasing the peak would require actual positive selection.

    So if the theory is correct it did increase it – but to their peak – which depending on various theories is a function of latitude or time spent under specialization or whatever else could drive positive selection.


  5. @luke – “These graphs would be more revealing if they were blown up to a much larger scale.”

    yeah, you could probably learn a lot if they were giganticized — and i presume if you were to use the program on which they were created (pajek), you could enlarge these graphs — but i think even at this smaller size you can see a lot: you can see, for instance, the conical structure that results from fbd marriage and how everyone can trace their lineage back to just a couple of founders. otoh, you can see how a looser mating system results in looser connections in the mexican village.

    re. pajek, btw — it looks to me like you can do many neat things with it like rotate the view and maybe follow certain connections. neato! (^_^)


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