family types and the selection for nepotistic altruism

it finally clicked in my head while thinking about polygamy what the importance of family types — nuclear vs. extended, etc. — might be in the selection for altruistic behavioral traits, especially nepotistic altruism or clannishness. i should’ve thought through polygamy sooner instead of putting it off, but hey — procrastination is heritable, too, so in the words of h. solo, it’s not my fault! (~_^)

the logic of the mating patterns/inbreeding-outbreeding theory goes that, given the right set of circumstances (i.e. certain sorts of social environments), selection for nepotistic altruism/clannishness ought to go quicker or be amplified by inbreeding (close cousin marriage or uncle-niece marriage) simply because there will be more copies of any nepotistic altruism genes (alleles) that happen to arise floating around in kin groups. in other words, inbreeding should facilitate the selection for clannishness…if clannish behaviors are being selected for in a population.

the thing is, though: the individuals carrying certain versions (alleles) of nepotistic altruism genes need to direct their nepotistic behaviors towards other individuals carrying those same alleles, otherwise their actions will be for naught. (yeah. kin selection.) if they direct their nepotistic actions towards people who don’t share the same alleles, then the actions will be “wasted” and the behavioral traits won’t be selected for — or at least not very strongly — and they might fizzle out altogether.

let’s take an imaginary society as an example: say everyone in our pretend population always marries their first cousins. their father’s brother’s daughters (fbd) even, so that we get a lot of double-first cousin marriage. h*ck! let’s throw in some uncle-niece marriages on top of it all. the inbreeding coefficients in such a society would be very high, and if clannishness was being selected for in our highly inbred population, the selection ought to move pretty quickly.

but suppose we separated all the kids at birth from their biological families and set them out for adoption by unrelated individuals — people with whom they likely did not share the same nepotistic altruism alleles. think: the janissary system, only on a population-wide scale. if we did that, there should be virtually no selection for clannishness despite all the inbreeding since pretty much no one’s nepotistic behaviors would be directed towards other individuals with the same nepotistic altruism genes. in this case, kin selection would just not be happening.

such a society does not exist, and i don’t think ever has. but there are societies out there with certain family types — namely nuclear families (or even post-nuclear family societies!) — which ought to have a similar dampening effect on any selection for clannishness.

northwestern “core” europe has had very low cousin marriage rates since around the 800s-1000s, but it has also, thanks to manorialism, had nuclear families of one form or another (absolute or stem) since the early medieval period — nuclear families are recorded in some of the earliest manor property records in the first part of the ninth century from northeastern france [see mitterauer, pg. 59]. on the other hand, eastern europeans, like the russians and greeks, while they also seem to have avoided very close cousin marriage for several hundreds of years (which is not as long as northwestern europeans, but is quite a while), have tended to live in extended family groupings. you would think that nepotistic altruism could be selected for, or maintained more readily, in populations where extended family members lived together and interacted with one another on a more regular basis than in societies of nuclear family members where individuals interact more with non-kin. societies comprised of nuclear families are more like my hypothetical janissary society above where the altruism genes that might’ve been selected for via kin selection instead fade away in the wash.

we have to be careful, though, in identifying nuclear family societies. the irish of today, for instance, are typically said to be a nuclear family society, but the extended family does still interact A LOT (i can tell you that from first-hand experience). same holds true for the greeks and, i suspect, the southern italians. i would say that these populations have residential nuclear families, but not fully atomized nuclear families which have infrequent contact with extended family (think: the english). the early anglo-saxons in england were also characterized by residential nuclear families — the extended family (the kindred) was still very important in that society. the individuals in a residential nuclear family society probably do interact with non-family more than individuals in a society structured around extended families or clans, but less so than a true nuclear family society.

the thought for the day then?: family types can also affect the selection for clannishness/nepotistic altruism.

that is all! (^_^)

previously: polygamy, family types, and the selection for clannishness and “l’explication de l’idéologie”

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inbreeding and the ancient hebrews (and the arabs)

the slitty eye said:

“Wonder why Arabs end up crazy about marrying cousins in the end…. On the other hand, I wonder if ancient Jewish had the same habit as well. After all, Yemen back then was under heavy influence of Judaism. Just wondering….”

did the ancient jews inbreed — and did they introduce those practices to the arabs? short answer: yes and probably kinda-sorta.

longer answer: the ancient hebrews did, indeed, inbreed. the twelve tribes of israel — ‘tribes’ — that should give you a clue right there! — married their cousins pretty regularly and practiced uncle-niece marriage, both of which is still technically ok in judaism today, i think (altho obviously not allowed in many states in america where they live).

robin fox devotes a part chapter of six in “The Tribal Imagination” to the inbreeding practices of the hebrews. here’s a bit of what he has to say [pg. 143]:

“Genesis 5, where the lineage of Seth is first spelled out, simply says of the successive male heirs that ‘they had many sons and daughters.’ Similarly, in the Gospel of Luke where the genealogy of Jesus is given back to Adam (Luke 3:23), only the line of firstborn sons is given. Jubilees spells out how these in turn found marriage partners. Kenan’s son Mahalelil marries the daughter of his paternal uncle Barakiel. The text spells this out, specifying explicitly that she is his ‘father’s brother’s daughter.’ This form of lineage endogamy then persists down the generations until Noah marries his paternal uncle’s daughter Emzara and begets Ham, Shem, and Japeth, the ancestors of the modern races….”

now, maybe none of these people ever really existed, or maybe they did. the genealogies and what they say about hebrew mating patterns may be accurate. but even if they are just inventions by the writers, the notable point is that the jewish people who wrote these texts obviously at least must’ve thought father’s brother’s daughter’s (fbd) marriage was the way to go.

continuing from fox [pgs. 143 & 145]:

“You will immediately be struck by the similarity to … the structure of paternal parallel-cousin marriage in Iraq and in the Arab world generally. And again the same principle applies: it is the way of keeping succession and inheritance in the paternal lineage: it is in that sense endogamic: marriage-in rather than marriage-out. (Cross-cousin marriage will always take you out of your lineal group.) It avoids marriage with the full sister (although the paternal half-sister can be allowed as an exception), but it does the next best thing in marrying the paternal first cousin….

“This form of marriage — with the father’s brother’s daughter — is allowed in Jewish law, and obviously the Pharisaic tradition that is enshrined in Jubliees endorses it fully. Marriage with the brother’s daughter — structurally the same thing (either a man marries his paternal niece or he passes the privilege on to his son) — both was allowed and occurred. Even if the paternal first cousin was not available, biblical tradition endorses second- or third-cousin marriages of the same type. Isaac married Rebeka, who was his father’s father’s brother’s son’s daughter, while Jacob married Leah, and then Rachel, who were his father’s father’s brother’s son’s son’s daughters. Keep the marriage in the patrilineal line: avoid marrying strangers, and totally avoid marrying gentiles. A lot of the Old Testament is about just this. Nehemiah’s great contribution to the Israelite’s rehabilitation after the captivity and exile was to prevent them from marrying strangers, thus regaining God’s confidence. Fans of Seinfeld will remember that when in desperation George decides to start an affair with a cousin, it is his father’s brother’s daughter he picks, and he explicitly spells this out.”


russian anthropologist, andrey korotayev, points out that most peoples around the world — even the ones who marry their cousins — think that fbd marriage is incestuous:

“[M]ost traditional cultures have a clear perception that marriage between a man and his FBD is incestuous. This is evident in the fact that in most languages a kinship term for FBD (or MSD) would be identical with a kinship term for one’s sister. This normally implies that marriage with a FBD (or MSD) would be perceived as equivalent to marriage with a sister (Korotayev 1999). There appears to be something here that Kronenfeld (pers. comm.) called a ‘cognitive problem’….”

so, how did the hebrews — and the arabs — wind up practicing fbd marriage?

“At the time of its origin, FBD marriage had nothing to do with Islam. The cognitive problem solution seems to have occurred somewhere in the Syro-Palestine region well before the birth of Christ. Rodionov (1999) has recently drawn attention to the fact that this marriage pattern is widespread in the non-Islamic cultures of this area (e.g., Maronites or Druze) and that it has considerable functional value in this non-Islamic context in facilitating the division of property among brothers after their father’s death (Rodionov 1999). Like Rodionov (1999), I believe that this marriage pattern could hardly be attributed to Islamic or Arab influence here. It seems, rather, that this marriage pattern in the Islamic world and the non-Islamic Syro-Palestinian cultures stems from the same source.

“But prior to the time of Islam, the diffusion of the FBD marriage pattern was rather limited. The only adjacent area where it diffused widely was the Arabian Peninsula (Negrja 1981; Kudelin 1994), where its diffusion can be linked with a considerable Jewish influence in the area well before Islam (Crone 1987; Korotayev 1996; Korotayev, Klimenko, and Proussakov 1999). In any case, by the seventh century, preferential parallel-cousin marriage became quite common among several important Arab tribes (Negrja 1981; Kudelin 1994). In the seventh and eighth centuries, an explosive diffusion of this pattern took place when Arab tribes, backed by Islam, spread throughout the whole of the Omayyid Khalifate. Although preferential parallel-cousin marriage diffused (together with Islam and Arabs) later beyond the borders of the Omayyid Khalifate, the extent of this diffusion was very limited. Hence, the present distribution of FBD marriage was essentially created by the Muslim Arab conquests of the seventh and eighth centuries….”

so, father’s brother’s daughter marriage was “invented” in the levant at some point in time b.c. and it’s likely that the jews introduced it to the arabs (who may have already been been marrying their cousins, just not their fbd) once they started migrating into and settling in the arab peninsula. why the arabs actually adopted it, i don’t know. they must’ve been impressed by the jews and their culture and, presumably, wanted to imitate it — just as other peoples did (persians, kurds, berbers, afghanis) when the arabs later conquered them.

see also: Hebrew Social Organization: Marriage

previously: jewish inbreeding and father’s brother’s daughter marriage

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muslim uncle-niece marriages

every now and again, the topic of muslim inbreeding comes up in britain because … well, ’cause it’s starting to get expensive for british society, healthcare-wise.

just the other day, steve jones pointed out the problems with muslim inbreeding at some conference. he also apparently said that: “It is common in the Islamic world to marry your brother’s daughter, which is actually closer than marrying your cousin.”

eh. there’s common and then there’s common. there’s a h*lluva LOT of cousin-marriage in the muslim world, for sure … but uncle-niece marriage? well, there’s sooome, but it’s not as common as amongst hindus — or even christians! — in india. this is from the 1992-1993 Indian Demographic and Health Survey:

scanning through’s tables, the only muslim uncle-niece marriage i can find are the ones in india (above chart), the siddis of india, and the hui (huizu) people of china.

that’s not really common, i’d say.

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