viscous populations and the selection for altruistic behaviors

part of william hamilton‘s theory of inclusive fitness/kin selection, which explains how altruism ever could’ve arisen at all (altruism here having a very specific definition), is that it should be possible for genes for altruism to be selected for if close kin interact regularly. kin don’t need to recognize one another for altruism to be selected for. as long as closely related individuals don’t move far from one another — that is, if a population is viscous — selection for altruism might happen.

i can’t see why this couldn’t also apply to lesser forms of altruism, not just the kind where you sacrifice your life for two brothers or eight cousins. you know what i mean. like: reciprocal altruism or nepotistic altruism. or just pro-social behaviors. whatever you want to call them. seems to me that nepotistic behaviors ought to be selected for more easily in viscous populations (if they increase fitness, of course).

and some populations are more viscous than others:

1) inbreeding populations where close relatives marry frequently over the long-term. mating with relatives must be highly viscous [insert sweaty/sticky incest joke here]. not only do the individual members of the population likely interact fairly regularly (can depend on your mating pattern), they pass many of the genes they share in common on to the next generations — who then also interact and mate. that’s what i call viscous! and, as you all know by now, some human populations inbreed more than others, and some have been doing so for longer than others. and vice versa. (see: entire blog.)

2) populations where extended families are the norm. societies where two or three generations of families all stay together, work together, play together. viscous. plenty of opportunity for nepotistic behaviors to be selected for. on the other hand, societies of nuclear families where more distant relatives are seen only once a year on thanksgiving, and then only to argue, and where your your heir is your pet cat…not very viscous. (see: family types and the selection for nepotistic altruism.)

3) socio-economic systems which push for close relatives to remain together rather than dispersing. if that sounds vague, that’s ’cause it is. sorry. i haven’t thought through it all yet. i do have an example of the opposite for you — a socio-economic system which pushed for close relatives to disperse — and that is the post-manorialism one of northwest europe. already by the 1500s, it was typical for individuals in northwest europe to leave home at a young age (as teenagers) and live and work elsewhere — often quite long distances away (several towns over) — before marrying. then it was not unusual for them to marry someone from their new locale. not viscous. conversely, many societies outside of the hajnal line (northwest europe) have had systems which encouraged the opposite.

food for thought.

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family types and the selection for nepotistic altruism

it finally clicked in my head while thinking about polygamy what the importance of family types — nuclear vs. extended, etc. — might be in the selection for altruistic behavioral traits, especially nepotistic altruism or clannishness. i should’ve thought through polygamy sooner instead of putting it off, but hey — procrastination is heritable, too, so in the words of h. solo, it’s not my fault! (~_^)

the logic of the mating patterns/inbreeding-outbreeding theory goes that, given the right set of circumstances (i.e. certain sorts of social environments), selection for nepotistic altruism/clannishness ought to go quicker or be amplified by inbreeding (close cousin marriage or uncle-niece marriage) simply because there will be more copies of any nepotistic altruism genes (alleles) that happen to arise floating around in kin groups. in other words, inbreeding should facilitate the selection for clannishness…if clannish behaviors are being selected for in a population.

the thing is, though: the individuals carrying certain versions (alleles) of nepotistic altruism genes need to direct their nepotistic behaviors towards other individuals carrying those same alleles, otherwise their actions will be for naught. (yeah. kin selection.) if they direct their nepotistic actions towards people who don’t share the same alleles, then the actions will be “wasted” and the behavioral traits won’t be selected for — or at least not very strongly — and they might fizzle out altogether.

let’s take an imaginary society as an example: say everyone in our pretend population always marries their first cousins. their father’s brother’s daughters (fbd) even, so that we get a lot of double-first cousin marriage. h*ck! let’s throw in some uncle-niece marriages on top of it all. the inbreeding coefficients in such a society would be very high, and if clannishness was being selected for in our highly inbred population, the selection ought to move pretty quickly.

but suppose we separated all the kids at birth from their biological families and set them out for adoption by unrelated individuals — people with whom they likely did not share the same nepotistic altruism alleles. think: the janissary system, only on a population-wide scale. if we did that, there should be virtually no selection for clannishness despite all the inbreeding since pretty much no one’s nepotistic behaviors would be directed towards other individuals with the same nepotistic altruism genes. in this case, kin selection would just not be happening.

such a society does not exist, and i don’t think ever has. but there are societies out there with certain family types — namely nuclear families (or even post-nuclear family societies!) — which ought to have a similar dampening effect on any selection for clannishness.

northwestern “core” europe has had very low cousin marriage rates since around the 800s-1000s, but it has also, thanks to manorialism, had nuclear families of one form or another (absolute or stem) since the early medieval period — nuclear families are recorded in some of the earliest manor property records in the first part of the ninth century from northeastern france [see mitterauer, pg. 59]. on the other hand, eastern europeans, like the russians and greeks, while they also seem to have avoided very close cousin marriage for several hundreds of years (which is not as long as northwestern europeans, but is quite a while), have tended to live in extended family groupings. you would think that nepotistic altruism could be selected for, or maintained more readily, in populations where extended family members lived together and interacted with one another on a more regular basis than in societies of nuclear family members where individuals interact more with non-kin. societies comprised of nuclear families are more like my hypothetical janissary society above where the altruism genes that might’ve been selected for via kin selection instead fade away in the wash.

we have to be careful, though, in identifying nuclear family societies. the irish of today, for instance, are typically said to be a nuclear family society, but the extended family does still interact A LOT (i can tell you that from first-hand experience). same holds true for the greeks and, i suspect, the southern italians. i would say that these populations have residential nuclear families, but not fully atomized nuclear families which have infrequent contact with extended family (think: the english). the early anglo-saxons in england were also characterized by residential nuclear families — the extended family (the kindred) was still very important in that society. the individuals in a residential nuclear family society probably do interact with non-family more than individuals in a society structured around extended families or clans, but less so than a true nuclear family society.

the thought for the day then?: family types can also affect the selection for clannishness/nepotistic altruism.

that is all! (^_^)

previously: polygamy, family types, and the selection for clannishness and “l’explication de l’idéologie”

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inclusive fitness

there’s some amount of confusion out there in the hbd-o-sphere (and beyond!) about inclusive fitness, which is understandable since the concept is not that straightforward — especially for those of us who are not scientists. i thought it’d try to dispel some of that misunderstanding by sharing my layman’s understanding of the concept — i think i grok the idea pretty well now (in a basic sorta way) — hope i don’t add to the confusion!

to start with, inclusive fitness is NOT some sort of biological law that organisms (including humans) will automatically be altruistic towards other individuals with whom they share a lot of genes (or vice versa if vice versa). if you hold that idea — and i get the impression that a lot of people do — get it out of your mind right now! you’ll feel better for it, trust me.

inclusive fitness is simply a concept or model which explains HOW certain social behaviors — especially altruism — might’ve evolved at all. period. full stop.

to understand inclusive fitness, we need to back up a sec first and think about fitness and what that is. very (very!) simply, fitness refers to an organism’s ability to survive and reproduce in a particular environment. traits — including behaviors — that enable an organism to survive and successfully reproduce will be selected for simply because that organism *is* able to survive and reproduce in its environment. this is natural selection. pretty simple, really, darwin’s dangerous idea.

when it comes to certain social behaviors in humans, it’s readily understandable why many of them were selected for. for example, mothers who devote a lot of time and energy to care for their infants — who obviously can’t take care of themselves and would die without any care — will be more fit than those mothers who don’t. the genes that predispose for those behaviors get selected for since children get half of their dna from their mothers, and the ones that are cared for are much more likely to survive.

what was — and to some extent still is — a big mystery is why other sorts of altruistic behaviors were ever selected for even though they hurt an organism’s fitness. how would self-sacrificing altruistic behaviors directed towards non-descendants ever be selected for? for instance, why on earth would somebody feel compelled to run into a burning building to save a neighbor (who wasn’t their child) at great risk to their survival and, therefore, to their fitness? we can see how “genes for altruistic behaviors towards offspring” could be passed down from mother (or parents) to kids, but how were genes for more general altruistic behaviors selected for?

here is where william hamilton‘s absolutely genius idea — inclusive fitness — comes in: perhaps certain social behaviors, which on the surface appear to reduce an organism’s fitness, and so shouldn’t get selected, might’ve been selected for if those behaviors were directed toward other close kin with whom individuals also share much dna in common.

everybody gets half of their dna from each of their two (for now, anyway) parents. but we also share dna with siblings and (blood-related) aunts and uncles and (wait for it…) cousins. given this inheritance pattern, probability says, for instance, that, in a randomly mating population, an individual should share 12.5% of their dna with a first cousin. so, if an individual with certain “genes for altruism” behaves altruistically toward their first cousins, odds are not bad that those first cousins might also have those same “genes for altruism.” here, then, we have a mechanism for how apparently self-sacrificing social behaviors can be selected for: since the altruistic individual 1) aids close kin with whom he shares much of his dna AND 2) probably in many instances shares the same “genes for altruism,” his being altruistic toward those kin 1) does not reduce his fitness AND 2) the “genes for altruism” get selected for, too. mystery solved. (see also: kin selection.)

one way i like to think of inclusive fitness — which, perhaps, isn’t entirely the right way to look at it, but i feel it helps my understanding — is that if you wanted to calculate an individual’s total fitness by adding up how many actual copies of his genes he passed on, you need to add together those found in his offspring and those in his close relatives’ offspring. in other words, you need to add together his own direct fitness plus his close relatives’ fitness to get his inclusive fitness (or his total fitness).

it seems likely that many of the altruistic (or spiteful, etc.) behaviors we’re talking about are pretty general in nature, i.e. not that specific behaviors like “be altruistic to your close kin” were selected for, but rather more like “be altruistic to the people around you, because they’re probably your close kin” were. it remains to be seen how much kin recognition plays a role in altruism in humans, but that’s a topic for another post anyway. for right now, i just wanted to make clear what inclusive fitness is — and isn’t. again, inclusive fitness is a concept which explains HOW altruistic behaviors MIGHT be selected for. it does NOT predict that individuals will DEFINITELY be more altruistic toward those with whom they share much dna.

the whole topic of inclusive fitness is, of course, much more complicated than all that, but i think this is a good basic intro to the concept. hope so, anyway! (^_^)

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inbreeding and the evolution of altruistic behavior ii

in Understanding Human History, michael hart did a real nice job of explaining how kin selection or inclusive fitness works and how “genes for altruism” could be selected for [pgs. 37-38]:

“For about a century after Darwin proposed his theory of evolution, the origin of altruistic behavior in animals remained a puzzle. It was not until the 1960s, when William D. Hamilton proposed his theory of kin selection, that a satisfactory explanation was given. That theory can perhaps best be explained by an example:

“Suppose a man sees his identical twin drowning in a river, and estimates (correctly) that if he were to jump in and try to save his brother the probability of success would be 80%, while the probability that he would die in the attempt would be 20%. Consider these two alternatives:

“a) Some of the man’s genes strongly dispose him to rescue his brother, and he therefore jumps in and tries to save him (‘altruistic behavior’).

“b) The man does not have genes that dispose him to rescue his brother, and he therefore stays on the shore and lets his brother drown (‘selfish behavior’).

“In case (b), exactly one copy of the man’s genes survives, and may later be replicated. However, in case (a), if the rescue attempt is successful, two copies of the man’s genes survive (one in his own body, one in his brother’s). As this will happen 80% of the time, on average 1.6 (= 0.80 × 2) copies of the man’s genes will survive. In this situation, therefore, genes that dispose a person to altruistic behavior will — on average — have more surviving copies than genes that dispose a person to act selfishly and will be favored by natural selection.

“Now consider a slightly different example. Suppose that the man on shore is a brother — but not a twin — of the person who is drowning. Case (b) will still result in one copy of his genes being preserved. However, since ordinary siblings share only 50% of their genes, if the man on shore succeeds in rescuing his brother then (on average) 1.5 copies of the man’s genes will survive. Since 80% of the attempts will be successful, case (a) will on average result in 1.2 (= 0.80 × 1.5) copies of the altruistic genes surviving. Since 1.2 is greater than 1.0, the altruistic genes will be favored by natural selection in this case too.

“Suppose, however, that the two men were not brothers, but merely first cousins. First cousins, on average, share only one-eighth of their genes. In this case, altruistic behavior results in only 0.9 (= 0.80 × 1.125) copies of the man’s genes surviving, and natural selection will therefore favor the genes for selfish behavior.

“The upshot is that a gene that disposes its bearer to behave altruistically toward a close relative can have a selective advantage over one that disposes its bearer to act completely selfishly. Furthermore, this can occur even though the relative never returns the favor, and even if the survival of the relative does not increase the group’s chances of survival. It is not necessary that either reciprocal altruism or group selection operate for kin selection to result in the spread of genes that dispose their bearer to act altruistically toward close relatives.”
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what’s missing from these examples is, of course, inbreeding. and depth of time.

take michael’s second example up there…

“Suppose that the man on shore is a brother — but not a twin — of the person who is drowning.”

…but let’s add that the parents of these brothers were first-cousins. that makes these two guys: brothers AND second-cousins (i.e. the children of two first-cousins). so they probably share not only 50% of their genes in common as brothers, but also 3.13% of their genes in common as second-cousins. so the “push” to jump in the water to save the brother/cousin must be somewhat stronger in the inbred pair than for the brother to save just a plain ol’ brother.

now let’s take this example of michael’s…

“Suppose, however, that the two men were not brothers, but merely first cousins. First cousins, on average, share only one-eighth of their genes.”

…but let’s make them double first-cousins rather than just first-cousins. what happens then?

well, while first-cousins probably share 1/8th or 12.5% of their genes in common, double first-cousins share … well, double that! … or 1/4 or 25% of their genes in common.

what happens to michael’s calculation then?

“In this case, altruistic behavior results in only 0.9 (= 0.80 × 1.125) copies of the man’s genes surviving, and natural selection will therefore favor the genes for selfish behavior.”

in the case of double first-cousins the calculation becomes 0.80 x 1.25 = 1.0. that’s just breaking even using michael’s example, but what if the odds of saving the cousin from drowing are better than 80%?

or what about the depth of time i mentioned above? what if the family of my double first-cousins has been inbreeding for a very long time. a very, very long time. like for fifty generations or more. then the relatedness between all the family members, including these double first-cousins, will be even closer. natural selection ought, then, to favor such double first-cousins jumping in to save each other.

as wade and breden showed (see also previous post), inbreeding can help to accelerate the rate of the evolution (or frequency in a population) of altruism genes [pg. 846]:

[T]he increase in matings between homozygous parents decreases the genetic variance within families, because these matings produce genotypically homogeneous arrays of offspring.”

repeated inbreeding in a family reduces the diversity (whoa!) of the allele types within that family, and if we’re talking about “genes for altruism” here, then the variety of those must get reduced within inbred families, too. in a population that consists of, say, ten inbreeding families, the one that has super-duper altruism genes that lead all of its family members to help each other out more than the members of the other families will have the advantage (provided selection favors that advantage for whatever reasons). and those super-duper altruism genes will no doubt eventually spread to the other families since, in reality, no family groups inbreed 100% of the time anywhere — there will pretty definitely be gene flow between families. so then you’ll get a whole population of super-duper family altruists (note that these people are NOT altruistic to unrelated individuals).

the human populations on earth today that inbreed most closely (within patrilineages) and often practice double first-cousin marriage — AND have been doing this for prolly at least a couple of thousand years (time depth) — are the arabs (who later spread these mating practices to the maghreb, the mashriq and far off places like iraq and afghanistan and all the other ‘stans) and some peoples in the levant like the druze. i think that, because of their long-standing mating practices, they are the prime human examples of wade and breden’s accelerated evolution of altruism thanks to inbreeding.

previously: inbreeding and the evolution of altruistic behavior and more on inbreeding and the evolution of altruistic behavior

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more on inbreeding and the evolution of altruistic behavior

remember this?:

those are a couple of graphs from wade and breden from when they did some mathematical modelling of the selection for “genes for altruism” under different circumstances (see previous post for more details).

the interesting graph is the bottom one which shows what the frequency of “genes for altruism” in a population would be IF selection was strong and IF the alleles in question were dominant. the gene frequencies are on the y-axis (at 1.0 the genes have reached fixation). the number of generations to get to the various gene frequencies is on the x-axis.

the interesting line on the graph for us is the solid line: those are individuals who are about two-times more related to one another than first-cousins in a randomnly mating population. that’s an exaggeration for most human populations, but it’s the most human-like of all the mating patterns they considered. the others are cloning, sib-mating (ewww!), and total outbreeding. so most human populations would be lower than that solid line, but not flatlining like the total outbreeding example. somewhere in between.

anyway. in my previous post i pointed out that after just 50 generations, there is already an increase in the frequency of “genes for altruism” in the solid line population. however, these models start at zero! in other words, the starting point they’re thinking of is if the populations start off with no “genes for altruism” at all. but that can hardly have ever been the case for any human population since altruistic behaviors are found in almost every living being on the planet!: plants, insects … even slime molds! not to mention our closest cousins, other primates.

so the baseline for the frequency of “genes for altruism” in any human population was probably never zero. who knows where it should be? 30%? 40%? 50%? 80%? i really don’t know. but not zero, anyway.

if we just say it was 50% — just picking an example right out of the hat — then the frequency of “genes for altruism” in the inbreeding solid line population increases much more sharply (i.e. the slope of the line is more slopey) over fifty generations than if we start the population off at zero. (look at the solid line between 0 and 50 generations versus 200 and 250 generations. there’s a much sharper increase in the latter group.)

i’m picking out 50 generation timespans, btw, because — at a very conservative estimate (1 generation=25 years) — arabs have been very closely inbreeding for ca. 56 generations (i.e. since at least mohammed’s days and most likely before).

anyway. that is all. (^_^)

previously: inbreeding and the evolution of altruistic behavior

update 05/30: see also inbreeding and the evolution of altruistic behavior ii

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two things

1) inclusive fitness — hamilton’s idea that your genetic success should be calculated by considering both your direct descendants AND other individuals who happen to share copies of your genes and whom you have aided in some way — means that individuals who are more altruistic towards those other individuals with whom they share a good deal of genes, close-ish family members being the most likely candidates, increase their total fitness. inbreeding, because it amplifies the relatedness between family members, can amplify the altruistic behaviors between them.

2) altruistic behaviors are behavioral traits that are selected for under certain conditions (selective pressures) because such behaviors pay off (i.e. increasing an individual’s fitness or inclusive fitness). there are many, many, many types of altruistic behaviors, including those that are on the “dark side” of altruism (bigotry, waaaaycism, genocide), so there cannot possibly be just one “gene for altruism.” inbreeding, because it amplifies the relatedness between family members, can make the evolution of “genes for familial altruism” easier/happen more quickly (see here and here).

(ok. so technically that’s more than just two things. so sue me! (^_^) )
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regarding the first point — inbreeding, because it amplifies the relatedness between family members, can amplify the altruistic behaviors between them — let’s take two examples: a population that breeds entirely randomly (doesn’t really exist in humans) and a population that inbreeds (cousins marry cousins regularly, for instance).

in the randomly breeding (diploid) population, the relatedness between the various family members looks like this. in such a population, first-cousins will probably share 1/8th (12.5%) of their dna in common; that’s an inbreeding coefficient of 6.25%.

first-cousins in the regularly inbreeding population will share a greater amount of dna in common because they share so many ancestors in common, so their inbreeding coefficients will be higher. for instance, some first-cousins from pakistan and saudi arabia, two societies with very long histories of cousin marriage, have inbreeding coefficients of 11%, almost double those in a randomly mating population.

so, all else being equal (which is obviously never the case), if we take a totally made-up example of an altruistic behavior — the sharing of bananas — one would expect to find that the first-cousins in the inbreeding population, since they are more closely related to one another, share more bananas with each other on average than the first-cousins in the randomly mating population. the first-cousins in the randomly mating population should share more bananas with each other than they do with their second-cousins, because they share more genes with each other than they do with their second-cousins — but overall their altruistic behaviors won’t hold a candle to the inbred first-cousins.

got that? (^_^)

macaque monkeys provide a good example of how more closely related family members are more altruistic towards one another than more distantly related family members. the closer the genetic relationship, the more grooming between two macaque relatives; the more distant the relationship, the less grooming

confused beetles provide a good example of how more inbred family members are more altruistic towards their close relatives than randomly mated family members are. in this case, we’re talking about an example of the “dark side” of altruism: randomly mated confused beetles cannibalize other related confused beetle larvae more than inbred ones.

steve sailer applied these ideas to humans way back in 2003. from Cousin Marriage Conundrum:

“Are Muslims, especially Arabs, so much more loyal to their families than to their nations because, due to countless generations of cousin marriages, they are so much more genealogically related to their families than Westerners are related to theirs? Frank Salter, a political scientist at the Max Planck Institute in Germany whose new book ‘Risky Transactions: Trust, Kinship, and Ethnicity’ takes a sociobiological look at the reason why Mafia families are indeed families, told me, ‘That’s my hunch; at least it’s bound to be a factor.’

“One of the basic laws of modern evolutionary science, quantified by the great Oxford biologist William D. Hamilton in 1964 under the name ‘kin selection,’ is that the more close the genetic relationship between two people, the more likely they are to feel loyalty and altruism toward each other. Natural selection has molded us not just to try to propagate our own genes, but to help our relatives, who possess copies of some of our specific genes, to propagate their own.

“Nepotism is thus biologically inspired. Hamilton explained that the level of nepotistic feeling generally depends upon degree of genetic similarity. You share half your personally variable genes with your children and siblings, but one quarter with your nephews/nieces and grandchildren, so your nepotistic urges will tend to be somewhat less toward them. You share one eighth of your genes with your first cousins, and one thirty-second with your second cousin, so your feelings of family loyalty tend to fall off quickly.

“But not as quickly if you and your relatives are inbred. Then, you’ll be genealogically and related to your kin via multiple pathways. You will all be genetically more similar, so your normal family feelings will be multiplied. For example, your son-in-law might be also be the nephew you’ve cherished since his childhood, so you can lavish all the nepotistic altruism on him that in an outbred family would be split between your son-in-law and your nephew.

“Unfortunately, nepotism is usually a zero sum game, so the flip side of being materially nicer toward your relatives would be that you’d have less resources left with which to be civil, or even just fair, toward non-kin. So, nepotistic corruption is rampant in countries such as Iraq, where Saddam has appointed members of his extended family from his hometown of Tikrit to many key positions in the national government….”
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what i got interested in was the flip-side of what steve talked about. in other words, if inbreeding leads to the sort of nepotistic behaviors we see in the middle east, maybe not-so-much inbreeding — or even outbreeding — leads to the opposite. lots of inbreeding in humans seems to lead to all sorts of family-oriented, clannish behaviors, not just nepotism. it even seems to, as randall parker pointed out, impede the development of democracy because everyone’s so focused on their extended families/clans/tribes. again, maybe outbreeding does just the opposite. i think there’s a lot of pretty good evidence pointing in these directions (see the Mating Patterns series down below ↓ in the left-hand column), but so far it’s all circumstantial.

furthermore, point number two from the top: inbreeding, because it amplifies the relatedness between family members, can make the evolution of “genes for familial altruism” easier/happen more quickly. not only are inbred populations of humans more likely to be more altruistic to their near kin than not-so-inbred populations because they are more closely related to one another (like the confused beetles), various “altruistic alleles” related to familial altruism ought to develop more quickly and be more frequent in the inbred populations (again, see here and here).

greg cochran’s not convinced. he said: “Your general notion that the degree of inbreeding does something, by itself, in the short run, is incorrect.”

i think he’s misunderstood my argument (well, how much can one communicate in a couple of comments to a blog post?). i am not arguing that “inbreeding does something by itself — except for potentially amplifying already existing altruistic behaviors (see the beetle example again). nor am i arguing that “inbreeding does something, by itself, in the short run.” no. of course, any “genes for altruism” would have to be selected for (or not) over some amount of generations.

wade and breden found that inbreeding accelerates the spread of altruism genes in a population, and that “genes for altruism” would already be on the increase after just fifty generations if the selection was strong and the genes dominant. populations like arabs in the middle east have certainly been inbreeding closely for well over fifty generations (i’ve over-estimated the length of generations at 25 years/generation to come up with a conservative guess of how long they’ve been inbreeding). and northwest europeans have been doing just the opposite for something like fifty generations or so. the one group is almost freakishly oriented towards the extended-family/clan/tribe; the other, as m.g. miles put it, to the commonweal.

i think there’s been an almost exactly opposite evolutionary history in terms of altruism in these two populations over the last one thousand years (how cool is that?!) — an evolution that’s ongoing, of course, since middle easterners are still inbreeding and northwest europeans are outbreeding more and more.
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greg also said:

“Imagine that in much of history, people lived in small groups that often fought with their neighbors. In that sort of situation, selection for group altruism is at least possible, since the group is full of close relatives, while the opponents are less closely related. Both sides are probably members of the same broad ethnic group or race, but that doesn’t matter: only the kinship coefficients matter.

“Suppose that many people emerge on to the stage of history with this impulse to fight for their side: in the past, this always meant closely related people. Now, with the emergence of states, they find themselves fighting in armies, which feel like their side, but are no longer closely related – not a bunch of cousins and such. It could well be that many individuals are actually willing to risk themselves for that state. They’re willing to die for truth, justice and the Assyrian Way. It’s not genetically smart, but their adaptations are wired for past circumstances….

Over time, this misfiring of altruism should decrease. Patriotism burns itself out. Dying for Assyria doesn’t do your close relatives any good at all. Some people will be more prone to this, some less, and that tendency will be heritable. Those with a tendency to volunteer (in the service of anything other than close relatives) should dwindle away over time.

yes. familial altruism (all sorts of behaviors!) can be misapplied in new circumstances. but i think that what greg describes would only occur IF you started off with a population with lots of smaller, somewhat related but inbred sub-groups which had lots of “genes for familial altruism” and then brought them together into a state. maybe like the roman empire. or any of the chinese empires.

BUT there are other sorts of altruism beyond familial altruism — like reciprocal altruism — tit-for-tat sorts of behaviors, for example.

if you started off, not with a population that consisted of sub-groups with lots of “genes for familial altruism,” but rather a population with more “genes for reciprocal altruism,” the patriotism may not be quite so artificial. i suspect — but have no real proof, of course — that northwest europeans are such a population.

to quote myself from over @west hunter [links added]:

“i wondered before, though, if an opposite of these sorts of kin-oriented altruism alleles might be certain types of reciprocal altruism alleles. you know: the ones behind tit-for-tat sort-of behaviors, etc.

“if you have a population that oubreeds A LOT (nw europeans from the middle ages onward) in which family and kin connections are downplayed (prolly because of the outbreeding) — AND you have the ‘right’ sort of selection pressures (something that selects for cooperation and corporate behavior, like medieval manorialism and farming in a cold climate) — then maybe the frequencies for whatever alleles code for reciprocal altruism increase because lots of reciprocal altruism increases your success at reproducing.”

if you kept warring, you would still burn through the most patriotic members of the group (think wwi and wwii), but you wouldn’t be left with clans at the end of the day (see the rest of greg’s comment below). perhaps bunches of self-oriented nuclear families/individuals, but not clans.

speaking of misapplied altruism, i think our reciprocal altruism is now being misapplied in the face of migrating mexicans and muslims and all sorts of third world populations who, on the whole, are not big into reciprocation.
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finally, greg said:

“But states are older in some places than others, and some have made greater demands than others. Imagine a region where states have been around longer, a place in which the locals have lived through empire after empire after empire. They should have had the patriotism bred clean out of them. They should feel altruistic about their families, maybe their clan – and nothing else.

yes, they do — middle easterners (the strongest of the inbreeders) and to a lesser extent the chinese (who also have a very long history of inbreeding) feel more altruistic about their families and their clans, but that’s not because they had the altruism/patriotism bred out of them. they’re sooo inbred (the muslims way more than the chinese) that they never had any patriotism in the first place! they have such strong drives for familial altruism that anything like patriotism doesn’t even enter into the picture. feelings of patriotism — nationalism — have historically been strongest amongst northwest europeans — the most outbred, civic, and “corporate” peoples in the world.

i think there are some really cool evolutionary histories that led to these differences in altruistic behaviors — differences which are some of the most profound, innate differences between human populations that are out there — the instinctive feelings guiding us in how to treat the others around us.
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see also: Giving Bigotry a Chance and Your country’s not your blood from henry harpending and greg cochran @west hunter (who seem to have caught the inbreeding/outbreeding & altruism bug! (~_^) ).

previously: inbreeding and the evolution of altruistic behavior and four things and which altruism genes? and inclusive inclusive fitness

(note: comments do not require an email. altruism. what’s in it for me?)

inbreeding and the evolution of altruistic behavior

michael wade (the beetle guy) and felix breden worked up some mathematical models of the possible frequencies of “genes for altruism” in several different types of inbreeding populations.

they took different degrees of inbreeding/outbreeding …

– mating with oneself or a clone (100% related)
– mating with a sibling (50% related)
– mating with a more distant relative (20% related, i.e. not quite half-siblings)
– no inbreeding at all (0% related)

… and via wizardry (i.e. advanced algebra) they worked out how “genes for altruism” would fare in each of these populations over the course of many generations. in other words, would altruism genes become more frequent or not in these various populations?

they factored in different parameters such as whether the gene(s) (alleles) in question were dominant or recessive, and whether the selection pressures on the alleles were weak or strong. weak selection apparently refers to those cases in which one “phenotype is slightly advantageous over another.” presumably strong selection means the opposite.

here’s what wade and breden found:

under weak selection — instances in which the altruism alleles only confer slight advantages to those who have them (top two graphs) — the altruism alleles really only increase in any significant way when the individuals self-mate (or mate with clones) or mate with their full-siblings. there’s some increase in altruism alleles in populations where mating occurs between individuals who are almost half-siblings and the alleles are dominant, but that increase really doesn’t become apparent until after several hundred generations of inbreeding.

under strong selection (lower two graphs), again the altruism alleles increase in frequency the most when the individuals self-mate or mate with full-sibs. however, there is also a marked increase in populations where mating occurs between individuals who are almost half-sibs AND the alleles are dominant. in fact, the slope really takes off after just fifty generations or so (solid line, bottom graph).

the authors conclude that: “Increasing the level of inbreeding can greatly increase the rate of change of gene frequency of the altruistic allele.”

i’m interested in the evolution of altruism in humans, though, and not many humans mate with themselves (yet) or even their full-siblings. what’s more common, as we all know by now, is cousin marriage.

mating with your first-cousin in a population where inbreeding doesn’t normally occur means your relatedness to your cousin is probably around 12.5%, much lower than the lowest inbreeding rate that wade and breden looked at (20%). however, in populations where inbreeding is frequent and regular, the coefficients of relatedness are much higher — for instance, some (many?) pakistani and saudi cousins have a coefficient of relatedness of around 22% (11% coefficient of inbreeding x 2). that’s pretty much the same as the lowest degree of inbreeding that wade and breden looked at.

i think it’s apparent by looking at human behavior that inbreeding affects the frequencies of altruism alleles in different human populations, but since we don’t even know what those alleles are yet, this hasn’t been proven one hundred percent. if wade and breden did their sums right, then my guess is that (at least some) altruism alleles in humans must be dominant and must confer a good deal of advantage to those who have them. in other words, if we could graph the frequencies of altruism alleles in humans who marry their cousins regularly over time, i think they would look something like the bottom graph above, although perhaps with a trajectory that wasn’t quite so sharp (since in no population does cousin marriage happen one hundred percent of the time in every generation).

the arabs, for example, have been marrying their first-cousins (often double-first-cousins) since at least mohammed’s days, or something like 1400 years ago. if we take a very conservative generation length as twenty-five years, that’s roughly 56 generations of inbreeding up to the present. at least. plenty of time, according to wade and breden, for altruism alleles to increase in that population — provided the alleles are dominant and the selection is strong.

a couple of other things to keep in mind: 1) like genes for height or intelligence, there are probably many genes for altruism, so we have to imagine some sort of cumulative effect of many genes on human behavior, i.e. we’d have to draw many charts to map the frequencies of many genes; 2) individuals in a population might share lots of alleles for reasons other than recent inbreeding, such as a population’s ancestors having gone through a bottleneck at some point in the past. you’d think that that could also contribute to the number of shared altruism alleles in a population.

update 04/30: see also more on inbreeding and the evolution of altruistic behavior

update 05/30: see also inbreeding and the evolution of altruistic behavior ii

previously: technical stuff and which altruism genes?

(note: comments do not require an email. citizens against altruism!)

mother’s brother’s daughter marriage

so, i found out that mother’s brother’s daughter (matrilateral cross cousin) marriage is, apparently, the most common form of cousin marriage globally.

i looked at father’s brother’s daughter marriage before, and noted one interesting feature in which ego’s paternal uncle (his father’s brother) got to pass his y-chromosome on to his daughter’s male children when she married her paternal cousin (because ego shares his paternal uncle’s y-chromosome). this is something a man wouldn’t normally be able to do (since his daughters don’t inherit his y-chromosome). so, fbd marriage is a really good deal for the paternal uncle.

what happens in mother’s brother’s daughter (mbd) marriage?

well, first of all, the y-chromosome doesn’t really matter here because ego doesn’t share a y-chromosome with any of his maternal relatives (unless everyone’s really inbred!).

in the case of x-chromosomes, ego inherits just one x-chromosome from his mother — an x that is a recombination of her two x-chromosomes. so, let’s track her two x-chromosomes.

in the case of ego’s mom’s maternal x-chromosome (i.e. the one she inherited from her mom), ego’s mother’s brother shares an x-chromosome similar, but not identical, to the one that ego’s mom has. (each of them inherited a recombined x-chromosome from their mother.) he passes an (almost) intact copy on to his daughter (the mbd), while ego gets part of his mom’s maternal x-chromosome recombined. the result looks like this (click on images for LARGER versions):

so there’s a few bonuses for several individuals here:

– some of ego’s x-chromosomal dna passes on to ego’s son via ego’s wife (the mbd) — normally a male doesn’t pass any x-chromosomal dna onto his sons;
– ego’s daughters get an extra amount of his x-chromosomal dna via their mother — another way of looking at it is that the mbd gets to pass on an extra amount of her x-chromosomal dna via ego;
– both ego’s mom and his maternal uncle get extra amounts of their x-chromosomal dna in their female grandchildren, and ego’s mom gets to pass some of her x-chromsomal dna on to her son’s male children, something she normally wouldn’t have been able to do.

ok. so that was one of ego’s mom’s x-chromosomes. what about the other one? the other one she inherited from her father, so she doesn’t share it with her brother. so it looks like this:

not very exiciting.

buuuuuut, what if ego’s dad had also married his mbd? that’s how they do it, ya know.

then it would look like this:

as you can see, ego’s father would also get to contribute some of his x-chromosomal dna to his female grandchildren’s genomes (via ego’s mother), something he wouldn’t have done otherwise.

so, that’s a short summary of what happens with the x- and y-chromosomal dna in mother’s brother’s daughter marriage. let me know if you see anything else of interest — or if you see an error in something i wrote here (i am experiencing a bit of a cupcake-induced brain fog after today’s festivities (~_^) ).

previously: father’s brother’s daughter marriage and coefficients of relationship – cousin marriage – grandparents

(note: comments do not require an email. or a family tree.)