where everybody’s fourth cousins

in response to the “people befriend their fourth cousins” study, smersh makes an excellent observation:

“You referenced some of this in your counter currents interview but this study makes things more clear.

Friends are as close to each other as fourth cousins.

Jews are also as close to each other as fourth or fifth cousins.

Therefore it is easy for Jews to make close friends by hanging out with other Jews.

Meanwhile, it is harder for gentiles to make close friends in mass societies, as people move around and no longer live in a village near a bunch of closely related people.

Certainly seems like it might explain a lot without implying a malicious intent on the part of certain parties.”

yes! maybe.

if it’s correct that people generally befriend their fourth cousins — and this is something that could vary between different populations (Further Research is RequiredTM) — then, perhaps, this could explain why places like iceland work so well, too. i don’t know what the average relatedness there is (does anybody know?), but presumably it’s something like fourth or fifth cousins as well. maybe then it IS really easy in such a place to have a — whatever — redistributive socialist system when it feels like almost anyone in your population could be your friend.

dunno.

btw, that counter currents interview was, in fact, originally a hoover hog interview that somehow got syndicated over on cc. just want to give credit where credit is due. (^_^)

previously: friendship and natural selection (and human biodiversity)

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friendship and natural selection (and human biodiversity)

i linked to this paper…

Friendship and Natural Selection

…in this past sunday’s linkfest, but, to be honest with you, i hadn’t actually read it. (yeah, i do that sometimes. ok, ok — a LOT of times!)

since then, a couple of people urged me to read the arXiv blogpost on it (thanks @DKshad0w and @SamoBurja!), which prompted me to read the orig. research paper and … wow! … mind. blown.

now, no, i’m NOT a geneticist — i don’t even play one on the innerwebs — so i’m not your gal for evaluating whether or not these guys — nicholas christakis and james fowler — have done their work right, but if they have, this is very cool stuff:

Pairs of friends are, on average, as genetically similar to one another as fourth cousins, which seems noteworthy since this estimate is net of mean ancestry and background relatedness.”

fourth cousins! note that these are (i believe) all white folks. the data are from the framingham heart study, but the researchers do say that they controlled both for relatives (i.e. that individuals might be “friends” with people who are, in fact, distant relatives) and ethnicity (eg. that italians might just be friends with other italians).

It is intriguing that genetic structure in human populations may result not only from the formation of reproductive unions, but also from the formation of friendship unions. This in turn has relevance for the idea of an evocative gene-environment correlation, proposed more than 30 years ago, which suggests that a person’s genes can lead one to seek out circumstances that are compatible with one’s genotype. Our results suggest that these circumstances could include not only the physical environment but also the *social* environment, and hence the genotypic constitution of one’s friends. As Tooby and Cosmides argue, ‘not only do individual humans have different reproductive values that can be estimated based on various cues they manifest, but they also have different association values.’ People may seek out particular, convivial social environments that affect their fitness.

i’ve been saying for a while now that the family types/social structures in which individuals are located ought to be taken into consideration when thinking about the fitness of those individuals and how natural selection might be working on different individuals living and reproducing in different sorts of social structures (individuals living in nuclear family structures versus large clan structures, for instance). i’ve mostly been thinking about family structures, but christakis and fowler are talking about friendship structures — alliances with non-family members. cool!

“The existence of excess genetic similarity between friends is also relevant to the growing area of indirect genetic effects, wherein the phenotypic traits of focal individuals are influenced by the genomes of their neighbors, in a kind of ‘network epistasis.’ In fact, our results support the idea that humans might be seen as metagenomic not just with respect to the microbes within them, but also with respect to the humans around them. It may be useful to view a person’s genetic landscape as a summation of the genes within the individual and within the people surrounding the individual, just as in certain other organisms.

yeah. just muse on THAT for a while. (~_^) and then try this on for size…

“[T]he human evolutionary environment is not limited to the physical environment (sunshine, altitude) or biological environment (predators, pathogens), but also includes the social environment, which may itself be an evolutionary force. Our finding that positively correlated genotypes are under positive selection suggests that the genes of other people might modify the fitness advantages of one’s own genes, thus affecting the speed and outcome of evolution.

did you get that? the researchers found that, the SNPs that were most common between the friends (the homophilic SNPs), have, indeed, been under recent positive selection:

“To test the hypothesis that homophilic SNPs are generally under recent positive selection, we use the Composite of Multiple Signals (CMS) score. This score combines signals from several measures of positive selection to create a single value that indicates the likelihood a SNP has been increasing in frequency due to selection pressure over the last 30,000 years (see SI). In Fig.3, we show that, after correcting for correlated outcomes due to linkage disequilibrium and for varying precision in the GWAS estimates (see SI), the top 20% most homophilic SNPs have significantly higher CMS scores than the other 80% (+0.07, SE 0.02, p = 0.003)…. In contrast, Fig.3 also shows that CMS scores are not significantly higher for the most homophilic SNPs in the strangers GWAS (–0.00, SE 0.02, p = 0.86). This suggests that the whole-genome regression model we use does not generate false positives…. In sum, it appears that, overall, across the whole genome, the genotypes humans tend to share in common with their friends are more likely to be under recent natural selection than other genotypes.

friendship and natural selection 01

friendship and natural selection 02
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with human biodiversity in mind, my question would be: do all peoples everywhere form an equal number of friendships with (technically) unrelated individuals? yes, i have an obsession with clannish peoples — but, seriously — do people who live in clans or tribes make as many “friends” as peoples who don’t? do they even have the opportunity? if not, what might this mean for natural selection in those populations?

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friends vs. family

*update below*

luke asks: “How important is friendship — between-non relatives that is — in highly inbred societies?”

good question.

there are two questions that relate to this on the world values survey (2005-2008 wave):

– For each of the following aspects, indicate how important it is in your life. Would you say it is: Family.
– For each of the following aspects, indicate how important it is in your life. Would you say it is: Friends.

i’m assuming that “friends” means non-relative friends to all of the respondents.

possible responses:

1 Very important
2 Rather important
3 Not very important
4 Not at all important

i looked at just those that responded “very important” to each question. i haven’t sorted any of the nations by ethnicity, so … you know … some nations (like the u.s.) are kinda mixed up ’cause they’re multi-ethnic.

here are the nations sorted by those who responded that family was the most important to them. all five father’s brother’s daughter (fbd) marrying societies in this world values survey wave (in red) are above the global average, four of them towards the top. of my “core” nw europeans (in blue), the netherlands, germany, france, and norway are all below the global average. the anglo nations scored, for the most part, below the fbd nations, but above the global average. i’m surprised at how low china and hong kong score:

wvs - family very important

and here are the nations sorted by those who responded that friends were the most important to them. the “core” europeans are all above the global average, but so are jordan, iraq, and morocco. again china and hong kong score very low:

wvs - friends very important

finally, here’s the data sorted by the difference between the “family” responses and the “friends” responses (family responses minus friends responses). towards the top are the societies with the widest difference between how important they feel family is versus friends — so they, presumably, value family much more than friends. towards the bottom are the societies with the smallest difference between how important family and friends are. all of my “core” europeans are below the global average, most well below. great britain, the netherlands, norway, and sweden are in the lowest quarter of the table, showing how — comparatively speaking — there’s not a very great difference in how these populations view family and friends. three of the five fbd marriage societies are above the global average. hong kong scores surprisingly low — as does ethiopia! maybe i shouldn’t be so surprised at that:

wvs - family friends very important - difference
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update 12/29: i took a look at the documentation of the values surveys for some of the countries for which i or someone else thought the results were kinda surprising (china, ethiopia, georgia, cyprus). here’s what i found:

– china: seems to be a pretty good quality survey. the researchers (from the Research Center for Contemporary China, Peking University) did conduct surveys in all regions of the country (i was concerned that maybe they only focused on beijing or something). two things that are a little concerning to me: 1) the sample size is 1,991. is that representative for a population of 1.3 billion? seems to me like it wouldn’t be, but what do i know about stats (not much)? 2) they interviewed more older people than younger people (aged 18-29). they figured that’s ’cause so many younger people are migrant workers and so just weren’t at “home” when these surveys were done. which is interesting given the results ’cause i would’ve thought that family would be more important to older generations in china than to younger ones, but perhaps not.

– ethiopia: there was a big problem with the ethiopia survey. i’ll just quote from the report [pg. 13]:

“Respondents (and interviewers) had IMMENSE difficulty interpreting scales with opposing statements on either side of a 10 point scale. They tended to give an answer of agreement or not for either statements separately rather than selecting a number to indicate their answer on the continuum between the two statements. A large amount of time had to be spent in each interview explaining (over and over again!) that a score below 5 indicated agreement in varying degrees of strength with the statement on the left, 5 and 6 meant a lack of agreement or neutral feeling towards both statements with a forced preference to one, and a score between 7 and 10 indicated varying degrees of agreement with the statement on the right. Attempts at utilising the ‘counting stones’ scale assistance technique AND attempts at adapted show card representations failed as respondents were too confused by the fact that there were two statements involved in each question.”

the friends and family answers were not on a ten point scale, but they were on a four point scale (very/rather/not very/not at all important). perhaps that confused the respondents as well?

also, the report says that the interviews were conducted in amharic. well, iwitbb** only 29% of the ethiopian population speaks amharic. hmmmmm.

**if wikipedia is to be believed.

– georgia: seems to be a pretty good quality survey, except — abkhazia and ossetia were NOT included (*sigh* — well, what can you do?) — neither were some regions that were occupied by the russians at the time (are they still?).

– cyprus: the respondents in cyprus comprised 550 greek cypriots and 500 turkish cypriots [pg. 24 of report]. however, iwitbb, ca. 80% of cypriots are greek while only ca. 18% of cypriots are turkish. having said that, i would’ve thought that the presence of so many turkish cypriots in the survey would’ve made the difference between the “family” vs. “friends” score higher. it would be interesting to know — which i don’t — the areas of turkey from which the ancestors of today’s turkish cypriots hailed.
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