assortative mating and the selection for high iq in (some) medieval european populations?

here’s a thought…

henry harpending has an interesting post up about how assortative mating amongst high- vs. low-iq individuals within a population could pretty quickly (in four generations) lead to different castes having high or low average iqs. he even drew up a couple of nice diagrams to illustrate his model, like this one:

what if … the new mating patterns in certain parts of medieval europe (strong outbreeding) PLUS the new socio-economic structure in certain parts of medieval europe (manorialism) led to increased assortative mating according to average iq in medieval europe?

what i’m envisioning is … the church banned cousin marriage, so you no longer automatically married one of your cousins — you had to go find a spouse somewhere. and, in fact, the medieval church strongly encouraged that marriage should be a choice made by the two individuals involved, not between parents or families or whomever.

on top of that, you have this manor system in which the lord (or monks) of the manor let out land to farmers to run (they then owed the manor service or rent). the lord of the manor specifically let out land to married couples, ’cause it took two to run a small farm properly, i.e. to carry out all the necessary duties. the nuclear family was it on medieval manors.

so who is a young and upcoming, hard-working, driven farmer going to seek out to marry? well, maybe he just marries the prettiest girl he can find — but maybe, if he’s smart, he marries someone like himself who is also hard-working and driven and wants to run a successful manor holding. they might even be attracted to one another. maybe it was exactly those sorts of couples — the smart, hard-working, industrious couples — who were the most successful and left the most descendants behind. maybe the combined outbreeding + manorialism environment helped to select for a population with a rather high average iq (’cause in the medieval period, the low iq folks would’ve mostly been weeded out).

contrast the medieval european world with almost any tribal or extended-family world where chances are you just marry your cousin or a fellow clan member and live in a compound with almost all of your relatives. how hard of an environment is that in which to survive or be a success? you’d think that lifestyle would actually carry dullards along rather easily — and the dullards might even be married off to their dull cousins and make even more dullards. most importantly, there’s no assortative mating across the whole population to strongly select for a higher average iq.

which populations in medieval europe had this combination of outbreeding + manorialism? england, france, germany, the low countries, northern spain, northern italy and, later, areas to the east like poland.

sound familiar?

edit: should’ve thrown other traits in there as well along with higher iq — industriousness, conscientiousness, all that stuff.

previously: whatever happened to european tribes? and medieval manoralism and genetic relatedness and “l’explication de l’idéologie” and family types and the evolution of behavioral traits and the middle ages

(note: comments do not require an email. medieval home sweet home.)

6 Comments

  1. Looking at the overall population, assortative mating fattens the tails, more -2 stdv and +2 stdv people around. Also 3, 4 and maybe even 5 stdv people that wouldn’t be around.

    Fischer’s fundamental theorem of natural selection states that:
    “The rate of increase in fitness of any organism at any time is equal to its genetic variance in fitness at that time.”

    Compact and neat hypothesis isn’t it? If high IQ is favoured in Darwinian terms assortative mating increases the rate of increase in IQ. Related or unrelated reasons could also provide adaptations that cause the population to out breed more or less. So lets say you have a population produced that has been under selection pressure for higher IQ, some other traits and outbreeding…. and the envrionment changes so that low IQ is favoured.

    Oh-uh.

    Reply

  2. @r.k. – “Related or unrelated reasons could also provide adaptations that cause the population to out breed more or less. So lets say you have a population produced that has been under selection pressure for higher IQ, some other traits and outbreeding…. and the envrionment changes so that low IQ is favoured.

    Oh-uh.”

    yeah, absolutely. these things can move in all directions. ruh-roh, indeed!

    Reply

  3. A nice hypothesis. It’d be hard to convince me that it gives those countries an overwhelming edge, though, partially due to other such eugenic effects happening elsewhere. Anatoly Karlin said, in his post The Ancient Greeks Weren’t All Geniuses, “The authoritarian family system, also seen in regions such as Germany, Sweden, Scotland, the Jews, Korea, and Japan (after ~1500), and substantially in 18th century Britain, seems to be highly eugenic in terms of selection for IQ and longterm planning.”

    To my knowledge this outbreeding + manorialism combination could explain the high IQs populations you bring up and authoritarian family systems could explain these countries that Karlin brings up, but other countries seem to need an explanation. The Irish are an obnoxious example: despite the problems you pointed out in Ron Unz’s article about Irish IQ and other topics, Irish IQ *has* risen quite a bit, and The Audacious Epigone gives a 99.7 estimate from the wordsum scores you discussed in your Irish American IQ article. In other words, the Irish genetic IQ seems pretty high, barely if at all lower than that of other European races. The Greeks also come to mind, having been subjected to neither of these eugenic effects but getting the Greek American estimate of 99.

    And I can’t think of a good reason for that.

    Reply

    1. “Irish IQ *has* risen quite a bit, and The Audacious Epigone gives a 99.7 estimate from the wordsum scores you discussed in your Irish American IQ article.”

      Can’t estimate a country’s IQ from the average IQ of its emigrants.

      I seriously doubt Ireland’s IQ is much more than 95.

      Reply

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s