behavioral genetics and twin studies

so this paper was making the rounds on twitter earlier in the week…

Demonstrating the Validity of Twin Research in Criminology [pdf]

…and everyone was like, “you have GOT to read this!” so i did. and, yeah, it’s really good! i highly recommend having a read of it.

the paper was written as a response to another paper entitled Pulling back the curtain on heritability studies: Biosocial criminology in the postgenomic era.

postgenomic? wt…? what planet do those guys live on?

anyway…Demonstrating the Validity makes many very right and very interesting points including the following:

1) a common assumption in behavioral genetics analyses is that human matings are random (they’re not — there’s a whole lot of assortative mating when humans go forth and multiply) and that assumption can lead to an underestimate of heritability estimates.

2) another assumption — the equal environments assumption (i.e. that both identical and fraternal twins share equal environments as kids) — leads to an overestimate of heritability estimates.

the authors of the paper show, however, that since these two assumptions are often found together in twin studies, that the over- and underestimates wind up more or less balancing each other out (see below — and see the paper!).

(i, of course, couldn’t help thinking that if assortative mating leads to underestimates of heritability, what would lots of inbreeding in a population do? so far, all twins studies have come from w.e.i.r.d. populations, though — afaik — so the inbreeding issue prolly doesn’t matter. but, if you should ever see some heritability estimates coming out of saudi arabia or sicily, heads up!)

other important points from the paper [my emphases in bold]:

When multiple divergent methods converge to illustrate a consistent finding, it is logically reasonable and empirically sound to accept as valid the results of the divergent methods. The primary reason for such a conclusion is the nonoverlapping assumptions underlying the various methods. This dynamic is illustrated in the convergence in findings between classical twin design studies and various molecular genetics methodologies. GCTA and CSG studies are examples of methodologies that are not subject to the same assumptions as classical twin designs and yet provide convergence in terms of the differential influence of genetic and environmental factors on a variety of behavioral phenotypes, including antisocial behavior. In direct contrast to the appraisal provided by Burt and Simons, the most cutting-edge research emanating from molecular genetics relies heavily on the findings of classical twin design studies and is continually providing empirical support for the validity of such studies.”

oh yeah!

also:

“We have shown empirically that violations of the assumptions of behavioral genetics studies do not invalidate heritability estimates. This is not a matter of opinion but a matter of mathematical evidence. Under certain conditions, our calculations and simulations revealed that heritability estimates will be slightly upwardly biased (probably no more than 5–10 percentage points). Under other conditions, heritability estimates will be downwardly biased (probably no more than 5–10 percentage points). Under the most likely condition, where multiple violations occur simultaneously, the biasing influences of assumption violations wash out, with upwardly biasing factors canceling downwardly biasing factors. Moreover, the overall pattern of findings flowing from the 61 studies examining the EEA revealed the same conclusions offered by our calculations and simulation data. Needless to say, no ‘fatal flaw’ in behavioral genetic methodologies or assumptions has been discovered and the conclusion that ‘all of these models are biased toward inflating heritability and underestimating shared environmental influences’ (Burt and Simons, 2014: 226, emphasis in original) is unequivocally incorrect.”

good stuff! read the whole thing here! and don’t miss all the supplementary materials here!

(note: comments do not require an email. identical. almost.)

occam’s razor

i just came into the hbd chick command center here, and the light wasn’t working and there was no power getting to my computer from the electrical outlet. so i thought…hmmm, must’ve blown a circuit breaker for some reason (although to be honest i couldn’t imagine why that should’ve been the case).

but that wasn’t the explanation. what had in fact happened was that 1) the light bulb had died AND 2) the power strip that my laptop’s plugged into had failed (long story).

what’re the odds of those two things happening just at the same time? i dunno, but i’m guessing on the high side. it still seems waaay more likely to me that it should’ve been the circuit, even though i know better now.

lessons? sometimes the most parsimonious explanation isn’t the right one. and hands-on investigation is probably a good idea.

sorry for getting all epistemological on you. won’t happen again!

(^_^)

herman the iron

forget about game of thrones! for blood and gore and violence, just read some medieval history!

here from galbert of bruges (bruges! the flemish city that’s installing an underground beer pipeline — see triple bonus in this past sunday’s linkfest. see? it aaaall gels together here on the hbd chick blog!), an account of a trial by combat in flanders in 1127.

the backstory: the count of flanders, charles i — “charles the good” — was assassinated on march 2, 1127:

“During the famine [of 1125], Charles distributed bread to the poor, and took action to prevent grain from being hoarded and sold at excessively high prices. Prodded by his advisors, he also began proceedings to reduce the influential Erembald family, which was heavily engaged in this activity, to the status of serfs. As a result, Fr. Bertulf FitzErembald, provost of the church of St. Donatian, the most important church in Bruges, masterminded a conspiracy to assassinate Charles and his advisors.

“On the morning of 2 March 1127, as Charles knelt in prayer in the church of St. Donatian, a group of knights answering to the Erembald family entered the church and hacked him to death with broadswords. The brutal and sacrilegious murder of the popular count provoked a massive public outrage, and he was almost immediately regarded popularly as a martyr and saint….

“The Erembalds, who had planned and carried out the murder of Charles, were arrested and tortured to death by the enraged nobles and commoners of Bruges and Ghent.”

one of the conspirators, guy of steenvoorde, was challenged to a trial by combat by herman the iron, who sounds awfully like the mountain from GoT. the duel took place near ypres on the 11th of april. from God’s Scribe: The Historiographical Art of Galbert of Bruges [pg. 106]:

“‘[E]veryone present went out to the manor where the combat between Herman the Iron and Guy had been called and where both sides fought bitterly. Guy had unhorsed his adversary and kept him down with his lance just as he like whenever Herman tried to get up. Then his adversary, coming closer, disembowled Guy’s horse, running him through with his sword. Guy, having slipped from his horse, rushed at his adversary with his sword drawn. Now there was a continuous and bitter struggle, with alternating thrusts of swords, until both, exhausted by the weight and burden of arms, threw away their shields and hastened to gain victory in the fight by resorting to wrestling. Herman the Iron fell prostrate on the ground, and Guy was lying on top of him, smashing the knight’s face and eyes with his iron gauntlets. But Herman, prostrate, little by little regained his strength by the coolness of the earth…and by cleverly lying quiet made Guy believe he was certain of victory. Meanwhile, gently moving his hand down to the lower edge of the cuirass where Guy was not protected, Herman seized him by the testicles, and summoning all his strength for the brief space of one moment he hurled Guy from him; by this tearing motion all of the lower parts of the body were broken so that Guy, now prostrate, gave up, crying out that he was conquered and dying.'”

=/

guy was later hanged having been found guilty via this trial.

(note: comments do not require an email. trial by combat.)

die ostsiedlung

und now is ze time on the hbd chick blog vhen ve dance über die Wichtigkeit der Ostsiedlung sprechen! (i switched to deutsch there, ’cause i wanted to end my sentence with a verb. just so you know.)

i’ve mentioned the ostsiedlung in passing before (see here and here for example), and i’ve even gone so far as to say that it’s:

“from a sociobiological point-of-view, probably the most underappreciated event in recent western european history. that and the reconquest of spain.”

that’s right! never mind your barbarian migrations of late antiquity! forget about them. expunge the barbarian migrations from your mind! the ostsiedlung (and outbreeding and manorialism and all the subsequent natural selection) is (largely) what created the intelligent, efficient, hard-working, gratification-delaying, ordnung-loving, not-so-violent (on a daily basis), consensus-democracy-preferring, slow life history, behind-the-hajnal-line tchermans that we know and love today (luv ya, germans!).

so, what the h*ll was the ostsiedlung?

the ostsiedlung, or “east settling,” was (from what i understand) the latter part of a broader ostkolonisation of central and parts of eastern europe by the medieval ancestors of the people we now refer to as The Germans. during late antiquity, germanic tribes had of course migrated out of southern scandinavia and central and eastern europe into western and southern europe. then, beginning in something like the 800 or 900s, they went and reversed that flow, and some of them began to migrate back into central/eastern europe. migration is one of the major forces in evolution, along with things like mutation and genetic drift, so from a sociobiological/human diversity perspective the ostsiedlung should definitely not be ignored.

it should really not be ignored because what you have to keep in mind is that the tchermans who were migrating back into central/eastern europe in the post-800s were quite different from the the barbarian tchermans who had migrated into western europe four hundred or so years earlier. the barbarian germans had been a bunch of inbreeding, tribal, feuding, kindred-based peoples. the germans who migrated eastwards later in the medieval period were already a population of (comparatively speaking) outbreeders hailing from a population based upon nuclear families (see here). that’s because (imho) these new-and-improved germans, who were coming out of the frankish heartland, had already been pressed for many generations through the outbreeding/manorialism meat grinder. different sorts of individuals had been selected for in this new social environment than had been successful in the old clannish society. and, crucially, these new germans brought that new environment with them when they settled the east.

the ostsiedlung was a huge self-sorting event in medieval europe. jayman and i like to babble about self-sorting a lot, but that’s just because it really is very important. large scale self-sorting of individuals is akin to assortative mating writ large. in fact, it must enable a whole lot of assortative mating. one enormous self-sorting event was the settling of the united states by hackett fischer’s four “folkways” (read: subpopulations) from britain. (others populations came, too.) the fact that various groups having unique characteristics established themselves in different regions of what would become the united states still affects the workings of our country today. on top of that, don’t forget that people in the u.s. have been continually self-sorting along those original settlement lines pretty much ever since the first settlers arrived from europe, so our regional differences are not going away any time soon.

anyway, the medieval ostkonlonisation and ostsiedlung were self-sorting events on a similar scale (the ostsiedlung being just the latter half of the ostkonlonisation really). the earliest part of the ostkolonisation was driven by kings (the carolingians mostly i think) conquering other germanic groups to the east (like the bavarians) in the 800s and 900s. apparently the establishment of ecclesiastical monasteries in the newly conquered territories was pretty heavy at this time. that’s an important little detail that i’ll come back to at a later date, so commit it to memory if you would. the latter part of the ostkolonisation, the ostsiedlung of the eleventh/twelfth to roughly the fourteenth centuries, was quite different in character. from The Germans and the East [pgs. 9 and 28-29]:

“[O]ne could say that ‘Germany’ grew out of the Carlingian East Frankish Kingdom between the Rhine and the Elbe by producing its eastern half on colonized Slavic and to some extent Baltic land. Thus the genesis of the German Empire took place within the perimeters of Europe’s ‘eastward expansion’ (*Osterweiterung*). It consisted, on the one hand, of Christian state-building in the Slavic-Hungarian East in the ninth and tenth centuries, and on the other — beginning in the twelfth century — of the migration and resettlement of the population from the older colonized areas west of the Elbe, the Bohemian Forest and the Enns…. [C]ontinuous new waves of German miners, peasants, craftsmen and merchants, as well as knights and clergymen, emigrated and permanently settled in countries neighboring Germany in the East and Southeast. Jewish emigrants from the West also took part in this migration process….

“Medievalists tend to distinguish two main colonization waves in the history of medieval Europe. The first embraced Carolingian Europe and occurred in the eighth and ninth centuries. The second, which covered almost the entire continent, began in the eleventh century and gained momentum in the following two or three centuries. Without ruling out the matter of a possible relationship between these two waves it is worth noting that the first had a military character, though not exclusively so, as it usually took the form of *Landnahme*, that is, the gain and occupation of conquered territories. The second wave was rather based — though again not exclusively — on economic causes….

“[P]eople went east in search of bread, freedom and adventure — in a word, a better life, as the Flemish settlers sang. These few were still the most industrious and mobile, the most dissatisfied with their social and economic status so far and, in a word, a sort of elite of the elite (indeed not only in the positive sense).”

here’s a really big map of the phases of the ostsiedlung [source – click on the map for a LARGER view]:

Deutsche_Ostsiedlung

so the early part of this migration of the medieval germans eastwards was military in nature — maybe a lot of soldiers from the west settled in the newly taken areas? — and, like i said, many monasteries/ ecclesiastical manors were established at this time. the latter part of the migration eastwards involved the settling of farmers, merchants, and artisans who wanted a better life in newly established manors and towns. the important thing here is not to think of these farmers, merchants, and artisans as comparable to the homesteaders of the wild west in america. they were not. the settling of the east did not at all involve independent migrants setting out on their own to strike it rich. the ostsiedlung was really more plantation-like in nature with the migrants signing up to be a part of some organized settlement project — a manor or a town or whatever. entire “new towns” were organized in this way and sprang up literally (used here in its colloquial sense) overnight in medieval eastern germany. while there were typically enticements for the new settlers to sweeten the deal (e.g. not having to pay taxes for the first five to seven years), they were still signing up to be a subordinate in a project. so, yes, these were people looking to better their lives — willing to work hard probably — but also apparently willing to be…a bit subservient. happy to follow the lead of the manor owner or whomever. (maybe this was less the case for merchants. dunno.)

whatever their average personal characteristics were like — and i could have them wrong here — they should at least be considered wrt the ostsiedlung as a self-sorting event.

btw, the new settlers were usually recruited not by the lords of the manors but by middlemen called “lokators”. here’s one organizing the work teams on a new settlement:

lokator

the reason that the hajnal line is where it is in eastern europe — and if you don’t know what i’m talking about, please see this post — is that that is simply the eastern limit of the ostsiedlung. from mitterauer [pgs. 45-46]:

“The most significant expansion of the model agricultural system [manorialism] in the Frankish heartland between the Seine and the Rhine took place toward the east. Its diffusion embraced almost the whole of central Europe and large parts of eastern Europe…. This great colonizing process, which transmitted Frankish agricultural structures and their accompanying forms of lordship, took off at the latest around the middle of the eighth century. Frankish majordomos or kings from the Carolingian house introduced manorial estates (*Villikation*) and the hide system (*Hufenverfassung*) throughout the royal estates east of the Rhine as well…. The eastern limit of the Carolingian Empire was for a long time an important dividing line between the expanding Frankish agricultural system and eastern European agricultural structures. When the push toward colonization continued with more force in the High Middle Ages, newer models of *Rentengrundherrschaft* predominated — but they were still founded on the hide system. This pattern was consequently established over a wide area: in the Baltic, in large parts of Poland, in Bohemia, Moravia and parts of Slovakia, in western Hungary, and in Slovenia.

Colonization established a line streching roughly from St. Petersburg to Trieste. We will come across this line again when studying European family systems and their diffusion. The sixteenth century witnessed the last great attempt to establish the hide system throughout an eastern European region when King Sigismund II of Poland tried it in the Lithuanian part of his empire in what is modern-day Belarus. The eastward expansion of Frankish agrarian reform therefore spanned at least eight centuries….

“Over against this ‘core Europe’ was a ‘peripheral Europe’ that did not acquire these structures until a relatively later date — or not at all. Here we can list Ireland, Wales, and Scotland in the West; the area of eastern Europe beyond the Trieste-St. Petersburg line that was unaffected by the colonization of the East; the entire Balkan region; southern Italy, which was formerly Byzantine, along with the southern part of the Iberian Peninsula that was under Moorish rule for so long a time. The political, economic, and social evolution of many regions in ‘peripheral Europe’ took a different turn because of their clinging to other, traditional agricultural systems.”

and here it is — the hajnal line. with the core area of where manorialism and outbreeding began in the early medieval period roughly outlined in green:

hajnal line - core europe

btw, wikipedia has this to say about the ostsiedlung (so it must be true!):

“The settlers migrated in nearly straight West-to-East lines. As a result, the Southeast was settled by South Germans (Bavarians, Swabians), the Northeast by Saxons (in particular those from Westphalia, Flanders, Holland, and Frisia), while central regions were settled by Franks. As a result, the different German dialect groups expanded eastward along with their bearers, the ‘new’ Eastern forms only slightly differing from their Western counterparts.”

if that was indeed the case, there might be further implications wrt to the self-sorting of medieval german populations, i.e. something to do with subpopulations of germans moving eastwards. so, stay tuned!

previously: big summary post on the hajnal line and behind the hajnal line

(note: comments do not require an email. another planned “new town” of the ostsiedlung.)