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

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