ashkenazi jews, mediterranean mtdna, mating patterns, and clannishness

here are a couple of thoughts on ashkenazi jews and the apparently high frequencies of mediterranean mtdna found in that population. i was going to include these in my response to prof. macdonald (prolly still will), but since that isn’t happening anytime soon, i thought i’d throw these out there. remember that these are just ideas, so don’t flip out on me!

if it’s correct that 80% of the mtdna of ashkenazi jews is of european — specifically mostly mediterranean, even more specifically very much italian — orgin, then it could very well have been that some male jews (traders?) from judea or alexandria married some roman women, either in or around rome or maybe even in southern gaul. as costa et al. proposed in their paper:

“Overall, it seems that at least 80% of Ashkenazi maternal ancestry is due to the assimilation of mtDNAs indigenous to Europe, most likely through conversion. The phylogenetic nesting patterns suggest that the most frequent of the Ashkenazi mtDNA lineages were assimilated in Western Europe, ~2 ka or slightly earlier. Some in particular, including N1b2, M1a1b, K1a9 and perhaps even the major K1a1b1, point to a north Mediterranean source. It seems likely that the major founders were the result of the earliest and presumably most profound wave of founder effects, from the Mediterranean northwards into central Europe, and that most of the minor founders were assimilated in west/central Europe within the last 1,500 years. The sharing of rarer lineages with Eastern European populations may indicate further assimilation in some cases, but can often be explained by exchange via intermarriage in the reverse direction….

“It is thought that a substantial Jewish community was present in Rome from at least the mid-second century BCE, maintaining links to Jerusalem and numbering 30,000–50,000 by the first half of the first century CE15. By the end of the first millennium CE, Ashkenazi communities were historically visible along the Rhine valley in Germany. After the wave of expulsions in Western Europe during the fifteenth century, they began to disperse once more, into Eastern Europe.

These analyses suggest that the first major wave of assimilation probably took place in Mediterranean Europe, most likely in the Italian peninsula ~2 ka, with substantial further assimilation of minor founders in west/central Europe. There is less evidence for assimilation in Eastern Europe, and almost none for a source in the North Caucasus/Chuvashia, as would be predicted by the Khazar hypothesis, — rather, the results show strong genetic continuities between west and east European Ashkenazi communities, albeit with gradual clines of frequency of founders between east and west….

The age estimates for the European founders might suggest (very tentatively, given the imprecision with present data) that these ancestral Jewish populations harboring haplogroup K and especially N1b2 may have had an origin in the first millennium BCE, rather than in the wake of the destruction of the Jerusalem Temple in 70 CE. In fact, some scholars have argued from historical evidence that the large-scale expansion of Judaism throughout the Mediterranean in the Hellenistic period was primarily the result of proselytism and mass-conversion, especially amongst women.”

just a reminder: the romans were outbreeders. they avoided cousin marriage. the proscriptions against cousin marriage were stronger earlier in the republican period than later, going from no marriage to third cousins or closer to first cousin marriage being allowed by the 200s b.c. but changes to mating patterns and people’s attitudes toward them take time. cosider how long it took for northern europeans to start following the church’s cousin marriage bans in the middle ages — around 300 years in the frankish kingdoms. also, cousin marriage is legal in germany today, and has been (mostly) since the days of luther, but cousin marriage rates remain very low. so i doubt if the roman cousin marriage rates shot up dramatically after the 200s b.c. (although you never know).

what i’m thinking is that the romans might have been quite okay with the idea of marrying their daughters off to some foreigners, especially since they didn’t have a tradition of marrying their cousins. jewish traders from the levant or wherever might not have had a hard time finding a nice roman girl to wed, either in rome itself or even in southern gaul perhaps. this could account for the “major wave of assimilation” in the north mediterranean that costa et al. think that they picked up in their mtdna analysis.

that only “minor founders” came from western/central europe might’ve had to do with the fact that northern europeans like the franks didn’t really start avoiding cousin marriage until the 800s, so they might not have been ready to marry some foreigners at all at that point. and that there was very little introgression whatsoever from eastern europeans should come as no surprise, given that it appears that eastern europeans continued to marry their cousins and be awfully clannish until quite late. when jews moved into eastern europe, they would’ve encountered a populace that barely intermarried between its own members, let alone with some outsiders.

if it’s correct that some jewish blokes married some roman chicks and then we got ashkenazi jews outta that combo AND if the theory of inbreeding/outbreeding/clannishness is right in any way (that’s two big ‘ifs’ there, in case you weren’t counting), then a funny thing to contemplate is that perhaps the jews who had moved northwards into germania in the very early part of the medieval period were some of the least clannish people up in that region, by virtue of the fact that they might’ve had a pretty heavy (outbred) roman ancestry while the northerners had barely begun to outbreed yet. i have to admit that this idea amuses me. (~_^) (just like the thought that much of the european introgression into african-americans likely came from the quite clannish ancestors of our southerners. heh.)

unfortunately, i don’t know what the mating patterns of jews in the levant (or elsewhere) looked like in second or first centuries b.c. not sure that we can guess by biblical proscriptions like those in leviticus either. those were from an earlier time, so it’s not certain they were being followed by our guys in italy. and there was a lot of behavioral variety among jews during this era, too — everything from hellenized jews to pharisees and sadducees, not to mention the jews who thought that jesus and his (universalistic) ideas were pretty cool, so i suspect that there must’ve been all sorts of mating patterns in the middle east at the time. so who knows how clannish (or not) the jews in rome were. no idea.

finally, icymi, i think the subsequent mating patterns of ashkenazi jews went like this. Further Research is RequiredTM.

in any case, mating patterns — and marriage traditions — matter.

see also: Genes Suggest European Women at Root of Ashkenazi Family Tree and Did Modern Jews Originate in Italy?

previously: what did the romans ever do for us? and historic mating patterns of ashkenazi jews

(note: comments do not require an email. roman jewish dude.)

polygamy, family types, and the selection for clannishness

i’ve been trying to think through polygamy and if there’s any potential there for the selection for clannishness like i think there is with long-term cousin marriage. (i think i might have sprained a parietal lobe while doing so. (*^_^*) ) i very much have subsaharan african societies in mind here, but, of course, polygamy occurs elsewhere, too.

on the surface it seems obvious that long-term polygamy ought to set the stage for the possible selection for clannish behaviors like cousin marriage (imho) does. like repeated cousin marriage, strict polygamy ought to narrow the relatedness within a population — the result of strict polygamy should be a greater number of half-siblings in a population than in a randomly-mating population, and, of course, half-siblings are more closely related to one another than non-siblings, so a society full of half-siblings could potentially lead to an accelerated selection for nepotistic altruism in a way similar to cousin marrying societies.

however, one big difference is that in polygamous societies generally — even in subsaharan african societies (where there’s a lot of polygamy) — people do not marry/mate with their half-siblings. (it does occasionally happen in some subsaharan societies, but only occasionally.) so, unlike in cousin-marriage societies, “genes for nepostistic altruism” (whatever they might be) might *not* become concentrated in family lineages. yes, there are a lot of half-siblings in polygamous societies, but any particular nepostistic altruism (“clannishness”) genes they might have (gotten from their fathers) will get diluted as they move out into the general population and marry non-relatives. if polygamy isn’t a driver of accelerated selection for nepotistic altruism (and i’ve rather persuaded myself that it isn’t), that could explain why subsaharan africans are generally pretty civic-minded, comparatively speaking. (the poor outcomes seen in african nations are perhaps more the result of other factors like low iq, high disease rates, etc., rather than clannishness. dunno. Further Research is RequiredTM.)

i should note here that polygamy in subsaharan africa is extremely variegated — in some societies, it’s typical for the first wife to actually be a cousin, and then the rest not. so there can be a layer of cousin marriage in amongst the polygamy. in other societies, cousin marriage is completely avoided. in yet other societies, the series of wives might be sisters (sororal polygyny), which makes all the offspring not only half-siblings (because they have the same father) but also cousins (because their mothers are sisters). here you would think that any selection for nepotistic altruism should very much be amplified. of course, in many subsaharan african societies — especially the polygamous ones — there’s often a lot of hanky-panky going on, so not all of the siblings will truly be half-siblings, etc. that’ll dilute your genes for nepotistic altruism right there.

another thing i also thought of regarding subsaharan and/or polygamous societies is the fact that all of the half-siblings don’t always grow up together. in patrifocal polygamous societies, yes — there you’ll have one man living with all of his wives (poor fellow!) and all of his kids, so all the half-siblings will be raised in the same place and interact with one another — and, presumably, continue to do so as adults. in matrifocal societies, a mother and her children reside with the mother’s family, not her husband and his family. this occurs in some polygamous societies, too.

it seems to me that, even if polygamy was a driver of accelerated selection for nepotistic altruism, such selection couldn’t possibly happen if the carriers of the clannishness genes don’t interact. if the half-siblings from polygamous unions don’t grow up together, or don’t interact much as adults, but rather with their (ordinary, i.e. not inbred) cousins, how would clannishness be selected for? it wouldn’t, i don’t think. or it wouldn’t be selected for in an amplified, accelerated way (which is what i think happens in the long-term cousin marriage scenario).

and that’s as far as i got with thinking through polygamy (i shall return to this topic, i’m sure). but thinking about the patrifocal vs. matrifocal family types got me to thinking about something else.

thought experiment: let’s say you eliminate cousin marriage from a population, but don’t eliminate the extended family. say you get rid of the inbreeding, but individuals continue to interact mostly with their close (extended) family members — more so than with the other members of society who are unrelated to them. you would think that it would take longer for clannishness to disappear — for “genes for nepostistic altruism” to get diluted in the population — than in a society where both cousin marriage AND the extended family were simultaneously eliminated.

i am, of course, talking about medieval western versus eastern europe here. the extended family was eliminated quite early in the middle ages in western europe via manorialism along with cousin marriage (serious changes to both were well underway in western europe by the 800s). in eastern europe, the cousin marriage bans appeared later simply because christianity had arrived later. and, especially the further east one goes (like into russia), the fewer pressures there were to eliminate the extended family. quite the opposite, really. for example, this was the situation in the baltic regions, including belorussia, in ca. the fifteenth century [pg. 440]:

a “…’kinship holding’, was collectively held by the extended family. Rural settlements often contained more than one kinship holding, and each holding was in turn subdivided among smaller households within the extended family….”

and in russia as late as the late seventeenth and early eighteenth centuries [pg. 444]:

“Russian manorialism was distinctive in several important ways…. In Russia…it was the peasant commune that allocated these taxes and obligations among the households. The village commune in Russia had emerged in the late seventeenth or early eighteenth centuries in response to increasing demands from the state and the landowning elite; peasant communes not only allocated obligations, but also chose their officials, held court, selected recruits for conscription levies, and kept written records of their activities. The communal clerk was sometimes the only member of his commune who could read and write….

“[O]n Russian manors, where hired labour was often not available, the peasant family had to personally perform labour obligations at the same time that it worked its own farm. This required large, often multi-generational, households with enough labour capacity to serve the simultaneous needs of both the manorial economy and the family farm…. As Steven Hoch has shown, however, life in the large household was hardly a rural idyll; household patriarchs formed a communal elite that ruled with despotic brutality, ruthlessly exploiting their families and denying any autonomy to the adults under them. At the same time, however, the large household also protected the peasant family from ruin.”

(hmmm. ever wonder where the russian love for [left-wing] authoritarianism comes from?)

even if eastern europeans/russians began to avoid cousin marriage around, say, 1000 (conversion to christianity), they didn’t quit residing in extended families and mostly interacting with their extended family members until, like, yesterday. (again, this pattern appears to be more pronounced the further east one travels.) so the dilution of nepotistic altruism genes in eastern european populations — via nepotistic behaviors being misapplied to individuals not sharing the same altruism genes (i.e. unrelated individuals) — didn’t happen as quickly as it did in western europe where people began regularly interacting with non-kin much earlier in the middle ages.

family types matter.

that’s all i’ve got for you for now. more soon! (^_^)

previously: start here and cousin marriage in sub-saharan africa and fulani, hausa, igbo, and yoruba mating patterns

(note: comments do not require an email. russian peasants.)