endogamy and genetic relatedness

this is just a short note — a little food for thought.

the following quote comes from catherine linley day’s FABULOUS ph.d. thesis, “Marriage Patterns in Two Wiltshire Parishes 1754-1914: Geographical Mobility, Consanguinity and Illegitimacy” [opens pdf]:

“In a theoretical isolated population of 500 people, after six generations all potential marriage partners would have been related to each other as 3rd cousins or closer (Fox 1967).”

the fox 1967 reference is to robin fox’s Kinship & Marriage: An Anthropological Perspective. i haven’t looked through fox’s book, yet, to see where linley day got this from.

in any case, it’s interesting to see how quickly endogamous mating patterns can lead to everyone in the population being quite related to one another (like in iceland or ashkenazi jews), genetically speaking. of course, no human population is totally isolated (right??), so you won’t find this exact scenario out in nature. but it’s interesting — and important — to keep in mind.

update 7/10 – calculating the inbreeding coefficient (see comments below):

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*update 07/11: john derbyshire’s found the source of this very informative map. hmmmm. for some strange reason i now seem to be associating the words “dark” and “horse” with the derb. (~_^)

don’t say i never gave you guys anything. (~_^) (no, i have no idea where the data came from!)

previously: size doesn’t matter

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libertarian crackers

nick land points out that it seems as though american libertarians tend to be of southern extraction — in other words, the descendants of those rustlin’ and fightin’ and inbreedin’ border reivers folks — and that they have that libertarian spirit because of their slight inbrededness. that makes a lot of sense! — and i’ve actually been thinking along those lines myself, too.

as a reminder, hackett fischer found that appalachia and areas further south were primarily settled by extended families/clans from the border areas of england-scotland, and that these folks had a looooong history of inter-clan (low scale) warfare. these northerners married their cousins or endogamously more than southern englanders did. and they brought aaaall these customs and traditions with them when they settled in the u.s.

the border reivers hadn’t been marrying their father’s brother’s daughter’s (fbd) for thousands of years like the arabs, so they weren’t tribal like the arabs. but they were clannish because they continued to marry relatively closely long after the christian church told them not to (probably something like the irish).

and being clannish means you don’t trust outsiders. and that includes THE GUBMENT.

i think it’s kinda funny that individuals from groups that are somewhat inbred (not as outbred as the southern english, but not as inbred as the chinese or arabs) and clannish — and must, therefore, be more related to their fellow family members than southern englanders and, thus, be less of individuals genetically speaking than southern englanders must be on the whole — feel as though they are very independent and individualistic persons. even though these sentiments (not liking the interference of outsiders) likely evolved in a clannish setting (i think).

for example, i noted this once before of taki of takimag. he once said:

The highly individualistic Greek is too self-seeking to submit easily to others’ dictates. His unruliness has helped him survive through the centuries of oppression, as well as to rise above adversity. But it has also made him unaware of the advantages of a communal spirit and true democratic attitudes. This has created a climate where cheating is a way of life, where the highest and lowest of citizens do not hesitate to use dishonesty, especially in politics.”

but the greek is NOT “highly individualistic.” what he is, and has been for probably a very long time, is quite genetically attached to his extended family, and so the greeks prefer their own extended families over unrelated extended families in all areas of life (thus the nepotism and the corruption) — and generally don’t trust anyone in THE GUBMENT! just like libertarian crackers.

it’s funny how these (what i think are) innate feelings of antipathy towards outsiders get interpreted by some of the holders of those feelings as being a streak of independence. it is independence in a way, but it’s independence from outsiders, not an individual indpendence like the english have which actually results in most or all of the individuals wanting to come together and form a government “of the people,” etc., etc.

disclaimer: pew tells me i’m a libertarian (not really, but i do sympathize), and i’m from one of the inbred peripheral groups of europe, so there you go — i’m practically living proof! (~_^)

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why mbd marriage amounts to less inbreeding than fbd marriage

in response to my post on why fbd marriage amounts to more inbreeding than mbd marriage (short answer: it results in more double-first cousin marriages), violet asks:

“I don’t understand why there can’t be double first cousins with mbd.”

good question. well, there certainly can be double-first cousin marriages in mbd societies, it’s just that the structure of mbd marriage doesn’t give the same push towards double-first cousin marriage as fbd marriage does.

what i should’ve done in the previous post on fbd (father’s brother’s daughter) marriage was to include diagrams of mbd (mother’s brother’s daughter) marriage along with the diagrams of fbd marriage, but to be honest i just got lazy (sorry!). so, without further ado, here is mbd marriage (you might want to have open the fbd marriage post at the same time):

ego (red triangle guy) marries his maternal first cousin, i.e. his mother’s brother’s daughter (mbd).

but who does ego’s brother (the triangle to the right of ego) marry? if he lives in a society in which mbd marriage is favored (china, for instance), and if there’s a female maternal cousin available, he’ll marry her (maybe/probably). in this case, that’s ego’s wife’s sister:

then what? well, in the next generation, unlike in fbd marriage, the kids of ego and his brother should NOT marry each other. the kids should marry their mothers’ brothers’ kids:

these kids are all first cousins, but they’re not double-first cousins (unlike in the fbd marriage scenario). the four kids do not share both sets of grandparents in common, whereas double-first cousins do.

also, you can see that there’s an additional party brought into this family tree — the yellow mom/aunt. she is not from ego’s patrilineage. she’s an outsider to some degree or another, and these wives that are brought in from the outside are why mbd marriage is often described as alliance building — different patrilineages build ties with one another.

so, the mbd marriage system doesn’t have the same push towards double-first cousin marriage as an fbd marriage system does. you can see this (i think) if you browse through the consang.net tables — there are more incidences of double-first cousin marriages recorded in fbd societies (arabs et al.) than in mbd societies (just about everybody else).

the reason any of this is good to know is because it is important to bear in mind that not all cousin marriage systems are the same — some result in more inbreeding or closer genetic relatedness between family members than others — and that should affect the evolution of “genes for altruism/other innate social aptitudes” in these populations.

previously: why fbd marriage amounts to more inbreeding than mbd marriage and tribes and types of cousin-marriage

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consanguinity and islam and democracy

i said last week that the week would be devoted to the woodley & bell consanguinity and democracy paper … and then i got distracted. typical. so, now, back on track…

aside from looking for any straight up connection/s between consanguinity and democracy (see previous post), woodley & bell also looked at consanguinity and democracy and several other possible factors that might affect the success of democracy in the nations included in the study: economic freedom, inequality, exports of fossil fuels (the “resource curse”), pathogen load (i’ll come back to that one!), and islam.

using path analysis, they found that islam seems to have a direct impact on democracy in muslim nations and ALSO that islam has an indirect impact on democracy via consanguinity.

recall that woodley & bell used two different indices of democracy: data from the polity iv project and the eiu democracy index. so they worked up two path analyses (click on charts for LARGER view). percent muslim for each country came from pew:

both analyses indicate: “that Islam has both direct effects on democracy and effects that are mediated by consanguinity, although the direct path from percentage Muslim to democracy [in the first model] only approached the conventional cutoff for significance (p = .096).”

from the paper (pg. 12):

“The largest impacts on consanguinity in the path models were produced by pathogen load and the effect of the percentage of Muslims within a nation. In the first path model the latter variable did not have a significant direct path to democracy, which suggests that its effects on democracy are largely mediated by consanguinity. Both pathogen prevalence and the influence of Islam have been described in the literature as having an inhibitory effect on democracy (e.g., Fincher et al., 2008; Fish, 2002; Fukuyama, 2001; Huntington, 1984; Thornhill et al., 2009). Here we indicate that these variables, which had previously been posited to have independent effects on democracy, are actually mediated by consanguinity.”

so, if a nation is islamic, that will affect how democratic it is (or not!), but what seems to be more important is if the population practices cousin marriage. it’s islam+consanguinity that is the key here, not just islam.

i think it makes sense that the effects islam has on democracy are “mediated” by how much cousin marriage there is in a society. cousin marriage directly affects the genetic relatedness between the individual members of a population, making individuals more related to their family members than would happen in an outbred society, while making those same individuals less related to non-family members, again unlike in an outbred society. i think this pretty clearly leads to clannish or tribal behavioral patterns which, as woodley and bell point out, are not conducive to liberal democracy at all.

islam doesn’t demand cousin marriage, but it doesn’t prohibit it either. since muslims are supposed to emulate mohammed (who married a cousin – see below), it probably rather encourages it. and anyway — which came first, cousin marriage or islam? yup. cousin marriage. one of mohammed’s wives was a cousin of his (his fzd) — and ali (yes that ali), who was mohammed’s cousin, married mohammed’s daughter, ali’s first cousin once removed. cousin marriage was very much the norm amongst the arabs in mohammed’s day. and, unlike roman catholic church policy makers, neither mohammed nor any imam since him (at least none that count) seem to have come down against cousin marriage afaik.

furthermore, good ol’ father’s brother’s daughter (fbd) marriage, the form of cousin marriage that leads to the most inbreeding, and that is still the preferred form amongst many muslims, was probably already well established amongst the arabs in mohammed’s day. fbd marriage was probably introduced to the arabs by jewish tribes from the levant who migrated into the arab peninsula starting in the second century b.c. so not only is cousin marriage amongst the arabs old, it’s really old — and it’s fbd marriage to boot. the arabs went on to introduce fbd marriage to the peoples of north africa, the mashriq and south asia (like the pakistanis and the afghanis).

my guess is that it’s not just the amount of consanguinity in a nation that negatively affects the success of democracy in that country, but the length of time the people have been practicing cousin marriage AND how close that cousin marriage is. like i said in the previous post, i think the evolution of “genes for altruism” comes into play here, not just the immediate genetic relatedness between the individuals in these societies, although it’s important, too.

so, i would bet that democracy would fare the worst in the levant, where fbd marriage originated, and the arab peninsula, where fbd marriage has been present for so very long, and that distance from that core region would predict better odds of democracy working at all.

kinda looks that way, don’t it? (eui democracy index 2011 – click on map for LARGER view):

syria, saudi arabia, yeman and oman have the worst scores for democracy in the muslim world (in the world!). iran, turkemenistan and uzbekistan have similar scores and all three of those countries were “arabized” in the early- to mid- seventh century a.d. pakistan was not brought under the arab sphere of influence until later (the early eighth century) and conversion to islam and arabization (and, presumably, the adoption of fbd marriage) took some time. this, i think, might partially explain why, even though pakistan today has similar consanguinity rates to saudi arabia, it does better as far as having a democratic state goes — the pakistani populations haven’t been marrying their fbd for as long as arabs.

similarly, at the other end of the “arab” world, north africans are relatively better at democracy than the saudis since they, too, were arabized — and adopted fbd marriage — comparatively late. the far flung islamic nation, indonesia, manages democracy fairly ok since they’ve hardly adopted fbd marriage at all, although they’ve probably been marrying their mother’s brother’s daughters for a while like other east asian populations.

previously: consanguinity and democracy

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invention of the modern world

there’s a very interesting series of lectures by alan macfarlane on youtube in which he outlines, from an historical/sociological p.o.v., the things we’ve been discussing around here: familialism/collectivism vs. individualism, civic societies, trust — and why the english are so odd in all these regards.

i’ve watched two so far — the one on friendship & kinship and the one on associations, trusts & civil society:



about halfway through the second video, macfarlane talks at length about, and very fondly of, the english public house. (^_^) i ask you: is there anything better than an english pub (<< been there)?! (correct answer: an emphatic no!)

the lectures were given @tsinghua university, beijing, so he offers some suggestions to the chinese audience on how they can get china to be modern just like the anglo world. unfortunately, he doesn't seem to have offered any biological solutions (at least not in the two videos i watched), so i doubt they'll have much luck.

still, macfarlane has a lot of info and some good insights to share, so they're worth the watch if you're looking to chill in front of the "tv" for a couple of hours.

he's also turning the lectures into a book, apparently, which is currently being serialized on The Fornightly Review. not quite half of the chapters have been posted so far.

previously: but what about the english?

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