Archives for posts with tag: familial altruism

i keep saying that i’ll define more clearly what i mean by “inbreeding” and “outbreeding,” but i never do. finally! — here i am, and i’m gonna do it! (^_^)

from the oxford dictionary of biology:

- inbreeding: “Mating between closely related individuals, the extreme condition being self-fertilization, which occurs in many plants and some primitive animals.” (see also wikipedia.)

- outbreeding: “Mating between unrelated or distantly related individuals of a species.”

great. but what’s “closely related” or “unrelated” or “distantly related”? self-fertilization doesn’t really apply to humans (at least not very often — i hope), so where to draw the line between “closely related” and “distantly related”?

i’m primarily interested in the evolution of altruism and other “innate social aptitudes” in man [pdf] — and here’s where inclusive fitness comes into the picture, btw — and the role that inbreeding and outbreeding might play in all that.

inbreeding in and of itself does not change the frequencies of genes in a population — it just moves them around, concentrating them in certain lineages. however, wade and breden showed in some mathematical wizardry modelling that, under certain circumstances, long-term, sustained inbreeding can, in fact, lead to increased frequencies of “genes for altruism” in a population.

wade and breden looked at four inbreeding scenarios: 1) self-fertilization (doesn’t happen in humans); 2) if the mating individuals shared half (50%) their genomes in common (like parent-offspring matings or sibling matings); 3) if the mating individuals shared 20% of their genes in common (this is somewhere in between first cousins and double-first cousins or uncle-niece/aunt-nephew); and 4) if the mating individuals shared no genes in common (not the typical pattern in human matings). most human populations do not practice parent-offspring/sibling matings — in fact, it’s usually avoided and considered by most as really icky. but quite a lot of peoples regularly marry first cousins, and some (in the arab world/middle east) even often marry double-first cousins — nor is the world short on uncle-niece pairings (southern india, for example — or hasidic jews).

wade and breden found that, under certain circumstances, long-term, sustained matings between individuals that share 20% of their genomes in common can lead in an increase in altruism genes in that population. first cousin marriage, probably the most common form of inbreeding in humans, is a little short of what wade and breden looked at, but it’s not terribly far away either (12.5% relatedness vs. 20% relatedness). you would think that the slope of the line for inbreeding at 12.5% relatedness would fall somewhere in between that for 0% and 20% (solid black line) on wade and breden’s lower graph here:

wade and breden 02 small

in clinical genetics, most researchers look at degrees of inbreeding that are between second cousins or closer, commonly referred to in the literature as consanguineous marriages. since i get a lot of my data on inbreeding from such studies, it’s kinda handy for me to define inbreeding as anything between second cousins or closer, but in reconsidering wade and breden’s results, i’m thinking that maybe i should only concentrate on first cousins or closer. for now i think i’ll stick to second cousins or closer, but i reserve the right to change my mind (it is a woman’s prerogative, isn’t it? still?).

so, on this blog:

- inbreeding = in a population, a general pattern of regular and sustained mating between individuals who are related to one another as second cousins or closer.

- outbreeding = in a population, a general pattern of regular and sustained mating in which individuals avoid second cousins or closer.

notice the “regular and sustained” bit. that’s important. we’re not talking here about occasional marriages between cousins. it has to be a regular practice in a society. i’m not sure what the frequency of the inbreeding needs to be. it will vary according to population size, of course — the smaller the population, the more closely related everyone’s going to be anyway (e.g. the yanomamo). in a larger population? — dunno. definitely when 50% of marriages are consanguineous over the long-term i think the frequencies of “genes for altruism” are going to increase pretty rapidly (i’ll come back to what sorts of altruism in another post). 30%? probably. 3%? not really.

outbreeding, too, needs to be “regular and sustained” to have any effect, i.e. to have a population slide back down wade and breden’s slope in reverse. one generation of outbreeding probably won’t have much of an effect, i think. evolution (natural selection) does take some time, after all. also, if one inbreeding group interbreeds with another inbreeding group, that’s NOT outbreeding according to my definiton. technically it is in biological circles, but if we’re talking about two populations that have been inbreeding for a long time and, therefore, have acquired a lot of genes for my “familial altruism,” then all they’re doing by interbreeding is swapping familial altruism genes. for example, if you’re the early medieval irish and are clannish because you’ve been inbreeding for who-knows-how-long, the “outbreeding” that you do with the vikings when they show up (probably) doesn’t count wrt altruism, because they’re a long-term inbreeding group, too.

to have any effect on the frequency of certain “genes for altruism,” outbreeding — like inbreeding — needs, i think, to be regular and sustained over the long-term, as it was with europeans (mostly northwest europeans) since the early medieval period (see also mating patterns in europe series in left-hand column below ↓ for more details) and, perhaps, some other groups like the semai in malaysia.

previously: inbreeding and the evolution of altruistic behavior

(note: comments do not require an email. hi there!)

Feeling Threatened Makes Us Nicer“Perceived menace makes people kinder to their kin but nastier to outsiders. Whether they use this strategy depends on family size.” – hmmm. maybe. part of the study was done on WEIRD students, so … hmmm.

Implicit Race Bias Increases the Differences in the Neural Represen-tations of Black and White Faces“[T]he ways in which Black and White faces are represented in this brain region [fusiform face area] differ for people with a stronger, implicit race bias compared to people with less or no bias. This implies that people with stronger, negative implicit race attitudes may actually perceive Black and White faces to look more different.” – or maybe people who perceive black/white faces to look more different have stronger, negative race attitudes? – original research article here.

Gene flow between Indian populations and Australasia ~4,000 years ago – from dienekes. see also A Three-Hour Tour from greg cochran. (i loved that show! (^_^) )

Genealogy Databases Enable Naming of Anonymous DNA Donors – oops. see also: Matching names to genes: the end of genetic privacy?

HBD: An Abbreviated History of Quisqueya and the Rise of Today’s Dominicans (and Haitians) – from nelson!

The Human Varieties Global IQ Dataset“I’m going to try and use Human Varieties to tabulate a more thorough, immediate, and accurate dataset of international intelligence studies. A dataset that is participatory, updated frequently, and available for download.” – jason malloy’s excellent goal to (single-handedly!) make global iq data open source. yay! (^_^)

Study Discovers DNA That Tells Mice How to Construct Their Homes“The research could eventually lead to a better understanding of what kind of internal reward system motivates mice to dig, or tells them to stop. And although humans do not dig burrows, that, said the leader of the three-person research team, Hopi E. Hoekstra of Harvard, could ‘tell us something about behavioral variation in humans.’”

‘Adventurous’ Woman Needed as Surrogate for Neanderthal Baby – holy cr*p! – via charles!

The Danger of Making Science Political“Many more scientists identify as Democrats than as Republicans…. [B]y some polls only 6 percent of scientists are Republican, and in the recent U.S. Presidential election, 68 science Nobel Prize winners endorsed the Democratic nominee Barack Obama over the Republican candidate Mitt Romney.”

People with low risk for cocaine dependence have differently shaped brain to those with addiction“New research from the University of Cambridge has found that recreational drug users who have not developed a dependence have an abnormally large frontal lobe, the section of the brain implicated in self-control.”

Many researchers taking a different view of pedophilia“Pedophilia once was thought to stem from psychological influences early in life. Now, many experts view it as a deep-rooted predisposition that does not change.”

Scientific evidence that you probably don’t have free will

Like Lance Armstrong, we are all liars, experts say“During a 10-minute conversation between two strangers, 60% lied at least once, Feldman reported in a 2002 study in the journal Basic and Applied Social Psychology…. Though men were more likely to lie to make themselves feel good, women more often lied to make their conversation partner feel good. Either way, Feldman said, the urge to make oneself likable and competent was a powerful motivator.”

Got milk? Then you might get a Nobel Prize, study suggests“[C]ountries in which people drink the most milk, per capita, also win the most Nobel Prizes, per capita….” – (~_^)

The Truth behind the HBD cult prt 1 – << only good for a laugh. no, really! – via jayman!

bonus: Portraits of ‘sworn virgins’ of Albania fascinate“Northern Albanian women … live and dress as men in order to provide for their families.”

bonus bonus: Great Oxidation Event: More oxygen through multicellularity

bonus bonus bonus: There Are Whales Alive Today Who Were Born Before Moby Dick Was Written – cool!

bonus bonus bonus bonus: Chinese migration to Angola tops 250,000

(note: comments do not require an email. albanian sworn virgin.)

the good professor harpending who, unlike me, actually knows what he’s talking about when it comes to population genetics, took a mathematical look at my suggestion (guess!) that there might have been enough time over the medieval period for genetic changes in the population to have resulted in the historical decline of violence in nw europe that pinker described in The Better Angels (see also eisner).

prof. harpending concludes that — yeah, sure — there might’ve been enough time (from the 1300s to the modern period) to effect such a genetic change. it would’ve been a bit of a push, but it could’ve happened:

“In the present case we need a response of 1/28 of a standard deviation per generation. Assuming an additive heritability of 0.5 (the true value is probably 0.8 or so from literature on the heritability of aggressive behavior in children) the selective differential must be about 1/14 or .07 standard deviations per generation. In terms of IQ this would correspond to a one point IQ advantage of parents over the population average and in terms of stature parents with a mean stature 0.2 inches greater than the population average. This would occur if the most homicidal 1.5% of the population were to fail to reproduce each generation.”

no, i didn’t understand most of that either.

i do understand that he thinks he went conservative in his calculation (i.e. using an additive heritability [<< two links there] of just 0.5 although he thinks it's probably more like 0.8), so that might mean that his calculation should actually be even more in the hbd-ist’s favor. in any case, he concludes that natural selection against “genes for violence” (or selection for “genes for nonviolence”) could explain the historical decline of violence in nw europe “if the most homicidal 1.5% of the population were to fail to reproduce each generation.” a bit of a push, maybe, but possible. (if they really did fail to reproduce.)

he suggests:

“Justice was famously brutal and harsh in Medieval and Renaissance England so this may not be an entirely meaningless exercise. In this excellent essay Peter Frost suggests that the nearly the same selection against violence occurred in the several centuries before the fall of the Roman Empire, and he provides grisly details of Roman treatment of criminals.”

that is one route to go — have the state simply remove the bad guys out of the gene pool.

i’d like to suggest another route (and this is where i’m going to start sounding like a broken record): that they got rid of clannishness in medieval nw europe.

why should getting rid of clannishness matter? because, for whatever reasons (i think the reasons are connected to inclusive fitness), clannish people are violent. blood feuds, honor killings, general obstreperosity — clannish people are just not peaceful.

why? i think it’s ’cause clannish populations are inbreeders and inbreeding alters the possible inclusive fitness payoffs. if you’re from an inbred group, you don’t have to stick your neck out for two brothers or eight cousins to increase your inclusive fitness. if your group is inbred enough, you might only have to be altruistic (in the biological sense) to just one brother or only four cousins (’cause you share that many more genes with your inbred relatives than individuals in an outbred population would, capiche?).

in an inbred population, violent clannish behaviors — which are just the flip-side of being altruistic towards one’s relatives (i.e. be really un-altruistic towards one’s un-relatives) — would/could quickly be selected for since the inclusive fitness payoffs are greater for each altruistic act. and this is exactly what wade and breden (1981) found: inbreeding can accelerate the selection for altruism genes (see also here).

so, to get rid of violence, you could get rid of clannishness. and to get rid of clannishness, you need to get rid of inbreeding. which is exactly what happened in medieval europe starting in the early part of the period. the roman catholic church, supported by secular authorities, banned cousin and other close marriages beginning in 506 (i think that’s when the first ban on cousin marriage was laid down).

enforcement of the various cousin marriage bans, which ranged from first to sixth cousins depending on what century you’re talking about, wasn’t easy — at least not in the beginning. the church, for instance, didn’t require that a marriage ceremony take place in a church until something like 1000 or 1100, so enforcement by the church in the early middle ages was probably patchy at best. however, there were LOTS of secular laws throughout nw europe banning close marriage, including very much so in anglo-saxon england. just a couple of examples: the law of wihtred from the 690s outlawed cousin marriage — and the punishment for cousin marriage in another anglo-saxon law from sometime the 900s-1000s was slavery for the perpetrators. again, difficult to know how well these laws were enforced; but that there were plenty of such laws indicates that the authorities were keen to do something about all this close marriage.

the law of wihtred is, i think, the earliest anglo-saxon law that i’ve come across which made cousin marriage illegal (at least in the part of england where the law of wihtred applied). so the push against inbreeding in anglo-saxon england started at least as early as 690 a.d. again, it may not have been very effective at that point, but england’s outbreeding project had begun by that point.

lorraine lancaster, still considered the authority on anglo-saxon kinship, concluded that, although its importance was beginning to wane (as indicated by a shift in who would be awarded wergeld in the event of a crime against a person, that person’s kinsmen or their guild), an individual’s extended kindred remained of importance in anglo-saxon/english society well into the 1000s. that suggests to me that “clannishness” was still around in the 1000s in england. feuding was definitely still a regular event.

the situation had changed quite a bit by the 1300s when nuclear families were all the rage and englishmen no longer relied so extensively on their extended families. people were still violent in 1300s england, but of course the shift from clannishness to non-clannishness — i.e. from violence to non-violence — would’ve taken some time. evolution doesn’t happen overnight.
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the state’s monopoly on violence and outbreeding don’t have to be mutually exclusive explanations for why there may have been a genetic change in nw europeans leading to a decline in violent behaviors. the answer might be both. like jayman said

“Inbreeding, and hence clannishness, can interfere with this process, because while the State is selecting for less violent people, clan conflict presents a counteracting selective pressure for people who are more violent (and can fight feuds).”

…so in places where inbreeding has not abated or did not abate as early as in england — the arab world/middle east, china (or parts of it anyway — h/t luke!), the highlands of scotland, the auvergne — the state hasn’t managed to quell violence as easily. the combo of outbreeding + an effective state seems to be a winning one. better yet if you don’t need such a very strong state (modern nw europe) and the population is just non-violent naturally.
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this is all just a theory, of course — theory with a small “t”. but, as cochran and harpending have said (h/t kiwiguy!):

“Whereas tests of hypotheses ought to be careful and conservative, generation of hypotheses ought to be speculative and free-ranging.”

so there! (^_^)

there ought to be a way of mathematically modelling my suggestion — i.e. that the historical decline of violence in nw europe is at least partially the result of the de-selection (if you can say that) of “genes for violence” due to a reduction in inbreeding — but since i’m pretty much numerically illiterate, i won’t be the one working up those models. i would think, though, that in addition to using the breeder’s equation in the calculation, you’d also want to factor in inbreeding/outbreeding somehow.

see also: Genetics and the Historical Decline of Violence?

previously: what pinker missed and “violence around the world” and outbreeding, self-control and lethal violence

(note: comments do not require an email. chinese clan house.)

so i think the connection between inbreeding (or outbreeding) and the evolution of the “innate social aptitudes of man” [pdf] works something like this:

inbreeding in and of itself does not change the frequency of genes (alleles) in a population [pg. 65], but it does move them around, concentrating them in certain family lines.

if, then, some sort of genetic mutation arises in one family line which, let’s say for the sake of argument, results in the carriers somehow behaving more altruistically towards their fellow family members than strangers, and this results in them being able to increase their inclusive fitness, then that genetic mutation will be selected for.

it will really be selected for (i.e. the selection rate will be accelerated) because of the inbreeding because: 1) since the inbred family will have greater than average numbers of this “altruism gene” because it is inbreeding, its members will likely execute a greater total number of altruistic behaviors towards one another and, so, they will really benefit fitness-wise from this new gene. also, 2) perhaps — perhaps — all else being equal, the inbred family members will feel even more strongly altruistic towards their fellow family members than an outbred family would since they are so much more genetically similar to their family members. to be honest with you, i’m not so sure about that second proposition, so i’m just going to skip it for now and focus on the first one.

wrt the first proposition, that the rate of selection of “genes for altruism” is faster in an inbreeding population is exactly what wade and breden found when they ran some models — the more inbreeding, the more rapid the selection of the altruism genes:

you can imagine why.

if you have a bunch of different families in a population, and one of those families possesses some sort of “familial altruism” gene which means that its members help each other out (or whatever) more than the members of the other families do, and this increases the fitness of a majority of this special family’s members, then they are simply going to be more successful than the other families. they’ll leave more descendants behind and, thus, more of those genes behind. IN ADDITION, if this successful family ALSO inbreeds, each of its members is much more likely to have at least one, or even two, copies of this familial altruism gene, so more members of this successful family will be even more altruistic to each other and voilà! — they’ll increase their fitness and success even more than they would have done without the inbreeding.

these familial altruism genes — genes that lead to behaviors in which individuals somehow favor their own family members over non-family members — and by family members i mean extended-family members — are only going to arise, of course, in a population in which there is more than one family. if you’ve got some tiny band somewhere that has absolutely no contact with any other group (doubt that’s ever existed), then my evolutionary scenario simply won’t happen. it’s the competition between the individuals from the different families that is driving this.

naturally, genes in any population — even an inbreeding one — won’t remain restricted to any one family for very long. no family anywhere inbreeds 100% exclusively, so if some successful familial altruism genes do arise in some inbreeding family somewhere, they will quickly spread to the other families in that population. thus, there is probably an ongoing familial altruism genetic arms race in inbreeding populations.

also, i think fewer familial altruism genes — or not such strong ones, perhaps — are going to arise in a comparatively outbreeding population. the accelerated selection due to the inbreeding won’t be there, nor will this arms race to keep one step ahead of the joneses when it comes to familial altruism. additionally, i think that in an outbreeding population, there’ll be greater selection pressures than in an inbreeding population for “reciprocal altruism” genes — i.e. genes which lead people to be willing to cooperate more with non-family members — since more of those sorts of behaviors will likely be required to be successful in life.
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so what do these “familial altruism” genes look like?

i dunno.

maybe there are differences in oxytocin-related genes? — the luuuuv hormone that “turns out to be the hormone of the clan.”

or — ya’ll know that i’m kinda fascinated by interclan fighting which is the flip-side of being nice to your family (i.e. be extra un-nice to your non-family) — so maybe one familial altruism gene is the “warrior gene” (MAO-A gene)? dunno.

one that i speculated about before is CYP21A2, the gene connected to congenital adrenal hyperplasia (CAH), a recessive genetic condition which affects the production cortisol which, in turn, affects the production of androgens (like testosterone) — notably, in the most common form of CAH, androgen levels are increased. the condition is a recessive one, so you need to have two copies of the deleterious allele to have the condition, but as i mentioned in my previous post on CAH, carriers with one copy of the allele have been found to have excess androgens — and androgens have been connected to aggression. (also, children with CAH have been found to have smaller amygdalae, so … they’re less fearful? don’t know if this also holds true for adults with CAH.)

increased aggression? fighting at the drop of a hat? interclan fighting? see where i’m going with this?

the interesting thing is — at least i think it’s interesting — is that there are different frequencies of CAH found in different populations. what we’d really want to know, of course, are the gene frequencies for CAH for different populations, but in lieu of those … here are some incidence rates of classical CAH in different populations [numbers acquired from or via here and here]:

1:282 – Yupik Eskimos, Alaska
1:2,141 – La Reunion
1:4,081 – Western Australia Aborigines
1:5,000 – GLOBAL
1:5,000-7,000 – Moroccan Jews
1:5,041 – Zurich, Switzerland
1:7,000 – Kuwait
1:10,866 – France (Whites)
1:10,866 – Italy (Whites)
1:11,500 – Sweden
1:11,764 – Netherlands
1:14,300 – Hungary
1:14,403 – Croatia
1:14,500-23,344 – New Zealand
1:14,869 – Western Australia
1:15,518 – Emilia-Romagna, Italy (Whites)
1:15,800-18,000 – Japan
1:17,098 – Scotland
1:19,939 – Minas Gerais, Brazil
1:20,000 – Norway

i dunno, but i see — maybe — the more inbred clannish fighters (yupik eskimos, moroccan jews, kuwaitis) having more cases of CAH than the more outbred peaceniks (new zealanders, norwegians, even northern italians). also…

- “The Texas data indicate a lower disease frequency in African-Americans when compared with Caucasians, and international data indicate higher frequencies in native Yupik Eskimos, Brazilians, residents of La Reunion, and Filipinos.” [source]

- “The prevalence of the disease [non-classical CAH] in Ashkenazi Jews was 3.7%; in Hispanics, 1.9%; in Yugoslavs, 1.6%; in Italians, 0.3%; and in the diverse Caucasian population, 0.1%.” [source] (non-classical CAH refers to a less severe form of CAH which might not get noticed until adulthood when it expresses itself in features like a woman having, perhaps, a bit too much facial hair.)

again, what we’d really want to know are the gene frequencies for CAH in different populations. then the über-human savants that we call population geneticists could do their math wizardry to see if these genes were under positive selection or not (zey hav vays av mayking ze data talk). (another interesting thing, btw, is that there are many different mutations in this gene which cause a range of CAH conditions from mild to severe — and different mutations are more common in different populations — see here and here and here for instance.)

of course, maybe these mutations in CYP21A2 aren’t being selected for for increased aggression/upside-down familial altruism. maybe it’s something else. witchel, et al., found that heterozygotes for mutated CYP21A2 alleles (i.e. individuals with just one copy of the cr*ppy gene) had increased cortisol levels and cortisol is, apparently, important for the immune system, so maybe these mutants simply survive infections better. others have found a possible connection between higher iq and CAH (masculinization = higher iq?) — see here and here and here — so maybe that’s it.

or maybe these genes are not being selected for at all. however, fertility rates of people (women) with CAH are low, so it seems like a strange bunch of genes to have around if they don’t have some sort of benefit.

previously: inbreeding and the evolution of altruistic behavior and looking for altruism genes and visions of altruism genes

(note: comments do not require an email. CAHt.)

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