this is a blog about human biodiversity (hbd) — the diversity found among and between human populations that has a biological basis. i blog about many areas of hbd, including genetic differences between individuals and populations related to both physical and behavioral traits, a few of which are listed here, many more of which can be found under “categories” and “tags” in the middle column toward the bottom of the page. pretty much anything that strikes my fancy really.

one of the features of the blog is an almost-weekly linkfest of hbd- and other-science-related articles. i generally aim for publishing a linkfest on a sunday, but sometimes it doesn’t happen until monday…or wednesday…or not at all for a couple of weeks. but there is always a linkfest eventually! (^_^)

my own personal interest, to which much of the blog is devoted, is in the evolution of social behaviors in human populations, specifically the evolution of altruistic behaviors (in both the scientific and layman’s sense of the word).

one way that altruistic traits can be selected for is via kin selection (see also this post on inclusive fitness). in kin selection, if a gene “for” altruism drives individuals to be helpful to close relatives, the frequency of the altruism gene will increase in the population, because relatives are likely to share genes with the altruistic individuals.

since all behaviors are heritable, including kin selected altruism, it seems logical that long-term mating patterns, which can alter the degrees of genetic relatedness between family members, might affect the selection for particular altruistic traits in populations. for instance, family members in populations having long-term and frequent close kin marriage (i.e. inbreeding populations) ought to share more genes in common with one another than those in a randomly mating population. if so, perhaps genes “for” altruism would spread more rapidly through the population, and perhaps the type of altruistic behaviors selected for would be very “family oriented” — nepotistic altruism, in other words. in populations practicing a consistent avoidance of close kin marriage over the long-term, family members ought to share fewer genes in common than those in inbreeding populations. in this case, perhaps behaviors that promote nepotistic altruism would not be so strongly selected for, and perhaps even reciprocal altruism might be.

this is the working hypothesis of the blog, then: that long-term mating patterns in human populations can affect the selection for certain social behaviors (in particular, altruistic behaviors) since they can alter the genetic payoff (the inclusive fitness) of those behaviors (via kin selection). change the long-term mating patterns of a population, and you change the selection pressures for altruistic behaviors. please, keep in mind that this is an IDEA and not any sort of confirmed biological theory.

much of my blogging has involved discussions of this idea as well as the compilation of “circumstantial evidence,” as it were, in support of — or negating — it. the broad social behaviors found in some populations appear to support the idea. for example, europeans (especially europeans from the northwest corner of europe, minus the irish, scots, and welsh) have been avoiding close kin marriage since sometime in the early medieval period. these same europeans — “core” europeans — exhibit very low levels of nepotistic altruism and are oriented toward the commonweal rather than some form of extended family: their family structures are based upon the nuclear family rather than larger extended families or clans; corruption and nepotism are low; civicness is strong; and universalistic sentiments are strong. on the other hand, populations in the arabized world (the middle east, maghreb, mashriq, pakistan, and afghanistan), have been practicing close kin marriage since at least the time of mohammed and likely even longer. these populations exhibit very high levels of nepotistic altruism and are oriented toward the extended family or clan rather than the commonweal: their family structures are based upon the extended family and clan; corruption and nepotism levels are high; civicness is weak; and particularism, rather than universalism, is strong. i’ve come to refer to these sets of behaviors as clannishness.

toward the bottom of the page (↓) in the left-hand column you’ll find links to many of the posts dealing with this inbreeding/outbreeding theory under “don’t miss” and the various “mating patterns in…” series. below i’ve linked to some key posts that, if you are interested in the topic, i don’t think you should miss.

thanks for stopping by the blog! and if you’re new here, welcome! (^_^) (and welcome back all you regulars!)

a good place to start is where i started — with steve sailer’s Cousin Marriage Conundrum.

in the case of europe, the church and secular authorities began to eliminate close cousin marriages in the early medieval period. since then, the general pattern seems to have been that the populations of “core” europe — northeastern france, belgium and the netherlands (except for coastal regions), central and southeastern england, northwestern germany, scandinavia (especially denmark), northern italy (especially on the north italian plain) and, to a lesser extent, switzerland — have rigorously avoided cousin marriage. populations in peripheral europe — ranging from the highlands of scotland and ireland, to southern spain and italy, greece and the balkans, and much of eastern europe — either adopted the idea to avoid cousin marriage late or continued marrying cousins right up until recently. in addition, the extent of (bipartite) manorialism in medieval europe is almost exactly coterminous with the area occupied by “core” europeans, and the manor system probably not only aided in the enforcement of the cousin marriage bans, but also altered the selection pressures on the populations in other ways.

whatever happened to european tribes?
big summary post on the hajnal line
medieval manorialism’s selection pressures
outbreeding, self-control and lethal violence
the radical reformation
– on the french: mating patterns of the medieval franks and le parallélogramme
– for details on the histories of the mating patterns in other regions of europe, please see the “mating patterns in europe series” below (↓) in left-hand column.

in the arabized world — which stretches from the maghreb through the middle east to the mashriq and afghanistan and pakistan — cousin marriage is very common and, especially in the middle east and the arabian peninsula, has been practiced since at least mohammed’s time and probably longer. the preferred form of cousin marriage in the arabized world is known as father’s brother’s daughter (fbd) marriage (or patrilineal parallel cousin marriage) and coincidentally leads to a very close form of marriage known as double-first cousin marriage. so, not only do populations in the arabized world practice a great deal of cousin marriage, and have done for scores of generations, their preferred form leads to particularly high levels of inbreeding.

father’s brother’s daughter marriage and double first-cousin marriage and why fbd marriage amounts to more inbreeding than mbd marriage
historic mating patterns on the arabian peninsula and hejazis vs. najdis (and vice versa)
reverse renaissance?
syria and syrian tribes
fbd cousin marriage and clans and tribes in iraq
consanguineous marriage in afghanistan
inbreeding in pakistan
there’s no place like home and kandahar vs. levittown
– for details on the histories of the mating patterns in the arabized world, please see the “mating patterns in muslim populations series” below (↓) in left-hand column.

(this isn’t quite finished yet, but will be soon!)