endogamy and genetic relatedness

this is just a short note — a little food for thought.

the following quote comes from catherine linley day’s FABULOUS ph.d. thesis, “Marriage Patterns in Two Wiltshire Parishes 1754-1914: Geographical Mobility, Consanguinity and Illegitimacy” [opens pdf]:

“In a theoretical isolated population of 500 people, after six generations all potential marriage partners would have been related to each other as 3rd cousins or closer (Fox 1967).”

the fox 1967 reference is to robin fox’s Kinship & Marriage: An Anthropological Perspective. i haven’t looked through fox’s book, yet, to see where linley day got this from.

in any case, it’s interesting to see how quickly endogamous mating patterns can lead to everyone in the population being quite related to one another (like in iceland or ashkenazi jews), genetically speaking. of course, no human population is totally isolated (right??), so you won’t find this exact scenario out in nature. but it’s interesting — and important — to keep in mind.
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update 7/10 – calculating the inbreeding coefficient (see comments below):

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kin recognition

greg cochran said: “[Y]our comment implicitly assumes that people somehow _know_ just closely related family members, and of course they don’t.”

i think he meant that kin recognition isn’t something innate in humans, although maybe i’ve misunderstood what he wrote (wasn’t completely clear to me). i disagree. i think there is good evidence that people do somehow “know” their relatives. it’s not a perfect system, but it does exist.

first, a little anecdotal evidence (which obviously isn’t scientific evidence in any way):

nearly everytime i go back to the “old country,” some stranger that i’ve never seen before in my life is sure to stop me in the street or in a cafe and say: “you must be one of the so-and-so’s.” this, you understand, happens in or near the town where my family is from — not at the other end of the country, of course (although come to think of it, i actually have another anecdote related to that which i’ll tell you below). two interesting examples of this come to mind. on one occasion, a very old man stopped and asked me if i was one of the “so-and-so’s” and he was referring to my maternal grandmother’s side of the family. because i’m pretty aware of my family history, i was able to confirm that i was, indeed, one of the “so-and-so’s.” he was quite old and he claimed that i looked just like my great-grandmother who he remembered from when he was a boy. the second example was a guy who told me i reminded him of his sister in both appearance and mannerisms, so we sat down and tried to figure out who each other was, and we eventually worked out that we were, in fact, second-cousins.

i said that this usually happens to me when i’m in the area where my family comes from in the “old country,” but here’s another example: one of my cousins, who like me did not grow up back where our parents came from, was on vacation in another country when a stranger she had never met before asked her if she was one of the so-and-so’s. this stranger was from the area where my and my cousin’s family came from, and he recognized her as one of us. (^_^)

(this sort of stuff that i’ve experienced my whole life is why this did not surprise me at all.)

so, people in traditional societies are attuned to appearance and personality in other individuals and they use them to identify relatedness (is this person a member of my family or of another family? if another family, which other family?). i’m sure their success rate is nothing like 100%, but they seem to me to be pretty good at it.

i think most americans are unaware that this sort of thing goes on in other societies simply most americans don’t do this. and that’s because the population in large parts of the u.s. is so jumbled up. why would you look for family resemblances in order to identify people in a place like new york or los angeles? pretty pointless. maybe it happens in areas of the country that have been settled the longest and haven’t experienced many changes in their populations. dunno.

but those are just a couple of anecdotes. now for some scientific studies:

– one of my faves: Grandma plays favourites: X-chromosome relatedness and sex-specific childhood mortality (posted about here). because of the differential inheritance of the x- and y-chromosomes, grandparents are not related to each of their grandchildren equally — and this seems to show up in the amount of time/resources a grandmother invests in each of her grandchildren. the more dna grandma shares with you, the more she’s going to invest in you. and vice versa. you’d think this must be some sort of innate behavior, ’cause i don’t imagine grandmas in nonliterate societies go around calculating the genetic relatedness between themselves and their grandkids.

The neuronal substrates of human olfactory based kin recognition — smell tests showing that women can identify their sisters vs. their female friends via odor.

The sibling uncertainty hypothesis: Facial resemblance as a sibling recognition cue“Within families, individuals reported greater closeness and altruism toward siblings who more closely resembled them.”

Kin recognition: evidence that humans can perceive both positive and negative relatedness“Participants made trustworthiness and attractiveness judgements of pairs of opposite-sex positive and negative self-resembling faces. Analyses revealed opposing effects of positive and negative self-resembling faces on trustworthiness and attractiveness judgements.”

– and from the chapter entitled ‘Cooperation, Conflict, and Kin Recognition’ in The Oxford Handbook of Evolutionary Family Psychology:

“[T]echnological innovations now make it possible to experimentally manipulate a postulated label of kinship — facial resemblance — to investigate phenotype matching mechanisms. In these studies, images of participants’ own faces are used to digitally alter the appearance of a set of faces, unfamiliar to the participants, to generate realistic, self-resembling stimuli (Fig. 20.2). Participants’ responses to selfresembling faces, relative to control faces, are then used as indices of cooperative and sexual inclinations toward kin (for a review of the methods and findings, see DeBruine et al., 2008).

“In an experimental task assessing monetary transfers between pairs of individuals, DeBruine (2002) found that participants were more trusting of selfresembling partners than controls. Furthermore, in a test of theoretical predictions that cooperation in ‘tragedy of the commons’ contexts — wherein there is a conflict between individual and collective interests — is enhanced by genetic relatedness, Krupp, DeBruine, and Barclay (2008) found group cooperation (as measured by monetary transfers to the group) increased as a function of the number of self-resembling members of the group.”

there are more studies out there showing that innate kin recognition is something real. there are also those that have found that it does not exist. (you can sift through some of them here on google if you like.) i’m inclined to believe that we can, on average, identify our close relatives (out to first-cousins maybe?) using resemblance clues with pretty good accuracy, but i’m happy to accept that the jury is still out on the matter (more research is required! (~_^) ).

something that greying wanderer has suggested is that maybe inbred peoples are better at this — i.e. have better innate skills to identify family — than outbred peoples. interesting idea. i like it!

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genetic similarity and altruism

there’s some good evidence that, on average, people:

– feel more grief over the death of a child who was most like themselves;

– care more for their grandchildren with whom they share the most genes (at least grandmas do anyway);

– are sexually attracted to individuals with whom they share genes if they don’t experience westermarck imprinting (or is it reverse imprinting?), and are more sexually attracted to those individuals with whom they share more genes.

all of this makes sense from an inclusive fitness point-of-view. on average, people really seem to behave according to the “two brothers or eight cousins” rule.

so i’ve been thinking, if you took two human populations with exactly the same evolutionary histories so that they had all of the same sorts and frequencies of genes — including those for altruism (and other social behaviors) — and then had one of the groups inbreed for a generation or two, the inbred group ought to start being more altruistic/whatever to their family members, on average, simply because they would share more genes with — be more genetically similar to — their family members than the non-inbred group members would be to their family members.

i’m guessing, then, that there are two things going on with inbreeding/outbreeding and altruism/other innate social behaviors:

– genetic similarity within a population directly and immediately affecting how people behave towards one another,
– and the evolution of genes for altruism over the longer term.

greying wanderer is ahead of me on this one (^_^):

“I think altruistic behaviour is the *product* of two separate things: relatedness and altruistic genes multiplied together, so the more related people are the less strong their altruistic genes need to be. If the human default is inbreeding then i think this makes more sense as an inbred group would then only have needed to develop very small amounts of altruism genes to create an altruistic effect. If so then it’s only when people outbreed that they need to develop *more* altruism genes to compensate for the drop in relatedness and it’s this that explains how those people can then come to display altruistic type behaviour towards non-kin.”

i thought before that maybe oubred groups evolved different altruism genes (i.e. ones for reciprocal altruism vs. familial altruism) rather than more altruism genes, but i like g.w.’s idea, too. definitely food for thought!

of course, genetic similarity+inbreeding+altruism is pretty much what steve sailer talked about in “Cousin Marriage Conundrum.” (^_^)

see also j.p. rushton’s genetic similarity theory.

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consanguinity + corruption = correlation

the awesome epigone has found a correlation of .44 between the amounts of (mostly) current consanguineous (first-/second-cousin) marriages in various societies as indicated by the data available on consang.net and perceptions of corruption by the people in those societies as found by transparency international (thnx, a.e.!). that’s higher than i would’ve guessed beforehand — i gave a bunch of reasons for that over @m.g.’s place which the epigone included in his post, so i won’t bother repeating them here.

i know that correlation is not causation, but it does “waggle its eyebrows suggestively and gesture furtively while mouthing ‘look over there,” so i’ll bet anyone a nickle — no, a dime! — that there is a connection here (and that connection is altruism/other innate social aptitudes [pg. 329+]).

i think audacious’ correlation would be even larger if there was some time depth to the inbreeding/endogamy data. what i’d like to see is:

– all the genes for altruism (and other innate social aptitudes) in man discovered so we (meaning teh scientists) can see the hbd differences in altruism, etc., in different populations and trace the evolutionary histories of all these genes in different populations. then someone could check for correlations between the gene frequencies and corruption (and other neat behaviors like nepotism).

in lieu of that, what i’d like to see is:

– all, or at least lots, of the people on the planet getting their dna sequenced so we (meaning teh scientists) can work out the degrees of relatedness within different populations so we (meaning teh scientists) could at least guess at the evolutionary histories of all these genes for altruism. then someone could check for correlations between the actual degrees of relatedness in different populations and corruption (and other neat behaviors like nepotism).

in lieu of that, what i’d like to see/do is:

– what the audacious epigone did but just with some time depth added to the inbreeding/endogamy data. plus, also, some consideration given to the fact that some forms of cousin marriage (i.e. fbd marriage) amount to more inbreeding than other forms of cousin marriage (e.g. mbd marriage).

for example, maybe two points could be awarded for each (likely) generation in which consanguineous marriages were common (haven’t considered what the cut off oughta be), and one point for each (likely) generation of endogamous marriage. zero points for marrying out. bonus point for fbd marriage. add ’em all up and then compare/contrast with corruption, et. al.

the problem is figuring out exactly how much inbreeding happened at any given point in the past for a population. i know there are ways to get at it by looking at dna — maybe what should be looked for are any correlations between runs of homozygosity in populations and corruption, etc. that would still be looking at a sort of proxy for the presence/frequencies of different sorts of genes for altruism, but it might be interesting anyway.

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linkfest – 06/10/12

Consanguinity and Corruption“Computing simple, unweighted averages for each country for which studies and surveys have been conducted and subsequently recorded on consang.net and then comparing them to Transparency International’s 2011 Corruptions Perception Index yields a correlation of .44 (p = 0).” – from the awesome epigone! see also steve sailer.

Does cooperation require both reciprocity and alike neighbours? – the answer is yes: “The researchers conclude that human societies can best achieve high levels of cooperative behaviour if their individuals interact repeatedly, and if populations exhibit at least a minor degree of structure.” – in other words, if the members of a society are related to some degree.

Re-Examining the “Out of Africa” Theory and the Origin of Europeoids (Caucasoids) in Light of DNA Genealogyopen access [pdf].

An Asian Origin for Human Ancestors?“Researchers agree that our immediate ancestors, the upright walking apes, arose in Africa. But the discovery of a new primate that lived about 37 million years ago in the ancient swamplands of Myanmar bolsters the idea that the deep primate family tree that gave rise to humans is rooted in Asia. If true, the discovery suggests that the ancestors of all monkeys, apes, and humans—known as the anthropoids—arose in Asia and made the arduous journey to the island continent of Africa almost 40 million years ago.”

Exercise benefits black girls less than whites, study shows“Physical activity seems a nearly sure way to prevent obesity in white adolescent girls, but does not have the same effect on African American girls, researchers say…. The study … falls in line with research that finds black women oxidize fat more slowly in response to exercise, and that their resting metabolic rates are lower than those of white women.”

[White] Americans’ heads have been growing, scientists say“Over the last 150 years or so, it appears that skulls got narrower from side to side by about 5 to 7 millimeters, and higher from top to bottom by an average of nearly 10 millimeters, Jantz said. And the overall size of the head has, on average, increased by an amount equivalent to the size of a tennis ball, he said.”

Menstrual huts protect Dogon men from cuckoldry“Women who practise the traditional Dogon religion, unlike those who are Muslim or Christian, spend five days a month around the time of menstruation in a highly visible ‘menstrual hut’. Strassmann tested paternity in 1700 Dogon father and son pairs and found that those who practised the traditional religion were four times less likely to be raising someone else’s son than those who practised Christianity.”

Lady Liaisons: Does Cheating Give Females an Evolutionary Advantage?“‘This is one of the most careful and most robust studies to explore whether polyandry is adaptive in females,’ says Tommaso Pizzari, a University of Oxford biologist who was not involved in the research. ‘The answer is: not really.'” – at least not in canadian song sparrows.

bonus: Plants may be able to ‘hear’ others

bonus bonus: Parasitic plants ‘steal’ genes from their hosts

bonus bonus bonus: Skeletons treated for vampirism found in Bulgaria – vampires!

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historic mating patterns in japan

readers (luke & jayman) request: what about the japanese? well, we aim to please… (^_^)

the japanese definitely have a history of cousin and endogamous marriages. i’m not sure, yet, how far back it goes (although i’m going to guess pretty d*rn far), but between 1912 and 1925 the consanguinity (first-/second-cousin) marriage rate for japan was 22.4% [pg. 29]. compare that to italy toward the beginning of the twentieth century or to some of the arab countries today. compare it also to the first cousin marriage rate amongst rural english folks in the 1870s: 2.25% (4.5% for the peerage).

but it’s been decreasing ever since (looks like a stock market crash – pg. 30):

by wwii the rate was only about 12.3%, and nowadays it’s like 4% (3.9% in 1983).

imaizumi, the author of the article to which i’ve linked above, also found in the early 1980s that 27% of recently married japanese folks had married endogamously, while amongst the oldest folks studied, 40% had married endogamously [pg. 39]. so endogamous marriages have also declined in japan over the course of the twentieth century. still, more than 1 in 4 japanese entered into an endogamous marriage in the ’80s (or maybe the late 1970s).

seems like the shintoists practice cousin marriage most frequently, followed by buddhists, and is lowest amongst catholics. farmers/fishermen, blue collar workers, the self-employed and people working in services (like transportation) inbreed the most, whereas white collar workers, salesmen and professionals inbreed the least.

note: the type of cousin marriage practiced in japan is mostly mother’s brother’s daughter (mbd) marriage as in china. more on that in the next post on japan. that’s important because mbd marriage amounts to less inbreeding (i think) than the arab type of cousin marriage (father’s brother daughter or fbd marriage) since all of the marriages do NOT occur exclusively in one lineage. in mbd marriage, at least more than one other lineage is involved.

the events of the meiji period obviously shook up the social structures in japan a LOT, but i wonder if cousin marriage/endogamy was officially — or even unofficially — discouraged in any way during that time period. i’m wondering if what happened in europe starting in the early medieval period regarding mating patterns has sorta been repeated in japan, only starting in the nineteenth century. -?-

goes to show, too, how rapidly cousin marriage rates can drop — within one generation in japan cousin marriage rates halved. maybe this could happen only amongst east asians who are big into conformity, but it’s something to keep in mind when trying to imagine what happened in europe in the medieval period, i.e. that things could’ve moved pretty quickly.

more anon!

previously: on the non-violent japanese of today

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linkfest – 06/03/12

Haplogroups as evolutionary markers of cognitive ability [pdf]

Memory training unlikely to help in treating ADHD, boosting IQ – h/t chris!

Corruption: The exception or the rule? – from m.g. @thosewhocansee.

Liberalism, HBD, Population, and Solutions for the Future – from jayman.

Is the Aboriginal (AUS) IQ really 62? – from chuck.

Nearly 1 in 6 Adult White Women on Antidepressants – from dennis.

Kin and Kindness

Monkey lip smacks provide new insights into the evolution of human speech“New research published in Current Biology by W. Tecumseh Fitch, Head of the Department of Cognitive Biology at the University of Vienna, supports the idea that human speech evolved less from vocalizations than from communicative facial gestures.”

bonus: A post-coital switch: Mapping the changing behaviors in the female fruit fly’s mind“Once successfully mated, a female moves from a highly sexually-receptive to a non-receptive state, actively rejecting further advances from males while altering her feeding and activity patterns…. Previous studies have shown that these behavioural changes are triggered by the male ‘sex peptide’ protein, a pheromone within the fly’s semen.”

bonus bonus: Earth took ten million years to recover from Permian-Triassic extinction“About 250 million years ago, pretty much everything died.”

bonus bonus bonus: Missing biologist surfaces, reunites with family – margie profet turns up! (^_^)

bonus bonus bonus bonus: Deeper Digging Needed to Decode a Best Friend’s Genetic Roots“[T]he DNA of modern dogs is so mixed up that it is useless in figuring out when and where dogs originated.”

bonus bonus bonus bonus bonus: For Some, Exercise May Increase Heart Risk – just the excuse i’ve been looking for. (~_^)

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