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?

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an over-simplification

the following is an oversimplification, but oversimplified models can be useful in thinking about complicated things, even if they don’t exactly represent what they’re supposed to be representing. i’ve been wanting to draw this out for myself for a while now, ’cause i’m a very visual thinker and i like pictures — even tho i’m not very good at drawing them myself. (~_^)

so … here is an (oversimplified) model of some altruism genes and inclusive fitness.

there are two altruism genes (alleles) here: a and A. (the capital letters here don’t signify dominance.) since humans (mostly) have two copies of every gene (allele), there are three possible combinations of these altruism genes that any individual might have: aa, aA, and AA.

ok. so far so good. now here comes the oversimplification…

in my little model, in the case of a famine, an individual with the aa combination does not share any of his food with his siblings. ever. so aa individuals always survive a famine, but their siblings do not. an individual with the AA combination always gives away all of his food to his siblings, keeping none for himself; so he always perishes in a famine, but his siblings always survive. aA individuals give away all of their food in half of the famine situations, so they perish half of the time while aiding their siblings’ survival half of the time.

obviously, genes don’t work this way. like i said … oversimplification.

anyway, so here’s what an average family in an average, randomly mating population would look like (edit: i guess i should’ve made two of them daughters. i’ll fix that later.):

what happens to the inclusive fitness — direct + indirect fitness — of each of these types of individual over the course of, say, ten famines?

first aa individuals. aa individuals never share any of their food with their siblings, so over the course of ten famines, the ten aa individuals will survive but none of their siblings will. so the direct fitness (not counting kids) of aa individuals = 10aa. indirect fitness (only counting siblings) = 0.

AA individuals always share all of their food with their siblings in a famine, so over the course of ten famines, the ten AA individuals will die, but all of their siblings will survive. so their direct fitness = 0. indirect fitness = 20aA (they each save one aa sibling and two aA siblings, but the aa siblings don’t count towards their inclusive fitness since they have no A alleles).

aA individuals share their food in 50% of the famines, so half of the time they survive, and half of the time their siblings survive. so their direct fitness over the course of ten famines = 5aA (themselves); indirect fitness = 5aa + 5aA + 5AA.

what does this all mean? well, if you add it up, it all looks like this:

– aa individuals ultimately save 20 of their own genes (10aa = 20a).
– AA individuals ultimately save 20 of their own genes plus 40 other genes (10aa + 20aA = 40a + 20A).
– aA individuals ultimately save 40 of their own genes (5aa + 10aA + 5AA = 20a + 20A).

so, maybe it pays (in a randomly mating population) to be somewhat altruistic, but not altruistic 100% all of the time? that makes sense. if you sacrifice yourself 100% of the time — well, does anybody do that? no. seems like that would be pretty quickly de-selected for (if that’s the right way of putting it). unless your familiy’s inbred, of course. that changes the situation. i’ll look at that in my next post.

also, take a look the AA individuals again. over the course of ten famines, they save twice as many alleles that they don’t even have as they do their own alleles. remember that. i’m gonna come back to that in another post.

that is all! (^_^)

previously: four things and technical stuff

(note: comments do not require an email. world’s most beautiful camel — descended from the camels of allah. she is kinda sweet! (^_^) )

technical stuff

here’s some really good, but technical, stuff (i’ve spared us all the formulae**) from “Inbreeding and the evolution of social behavior” by richard michod. the essay can be found in “The Natural History of Inbreeding and Outbreeding.”

pg. 74:

“Social evolution is interpreted here in a narrow but important sense as the evolution of behaviors that benefit the group but are costly to the individuals that perform them. The term altruism has been applied to such behaviors. However, it should be realized that most of the theory to be discussed applies to the evolution of intraspecific interactions generally. In other words, the effects of the behavior under study, on the fitnesses of both the donor and the recipient, can take any sign.

i mentioned this in my recap post of a couple of months ago. inbreeding and outbreeding (should) not only affect altruism, but all sorts of social behaviors. i’m also particularly interested in how mating patterns affect the social control of reproduction in human societies (think: burkas), but that’s just me.
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pgs. 84-86:

“Kin selection can be viewed, and explicitly modeled, as a selection process involving within-family and between-family selection….

By definition, altruism is selected against by within-family selection (individual selection) and favored by between-family selection, since the average fitness of a family is directly proportional to the frequency of altruists within the family. Indeed, it can be shown that Hamilton’s rule translates into the condition in which between-family selection overrides within-family selection (Wade 1980)….”

this makes intuitive sense — at least it does to me. if you only had one human family on the planet — mom, pop, sis and junior — they would only be in competition with each other for successfully reproducing their genes. however, throw the jones family in next door, and our first family, who are all more related to each other than they are to the joneses, are now all in competition with the joneses. thus, altruism genes are more likely to spread within our first family when they have some competition from outside.
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“Breden and Wade pointed out that inbreeding eventually fixes the population for two family types resulting from matings between like homozygotes (AA x AA, aa x aa). Matings between like homozygotes result in families that have no genetic variation in them. Consequently, they concluded that inbreeding generally decreases the average within-family variance. The two types of families produced by matings between like homozygotes are also maximally different from each other in frequency of the altruistic allele and in average fitness. Consequently, inbreeding increases the between-family variance. Both these factors, that is, the decrease of within-family selection and the increase of between-family selection, have the effect of making the evolution of altruism easier. This effect was also emphasized by Boorman and Levitt (1980: 350). They concluded that ‘…a high degree of inbreeding may be expected to favor sib altruism over the random mating case….’

“Conclusions. In conclusion, the evolution of altruism is favored by between-family selection and disfavored by within-family selection. Inbreeding can make the evolution of altruism easier by increasing the between-family variance and decreasing the within-family variance….”

so, inbreeding makes “the evolution of altruism easier.” that’s ’cause, for instance, if two members of a family have altruism genes and they inbreed, then the altruism genes are more likely to be passed down to the next generation. more so than if only one parent had an altruism gene. then there would only be a 50-50 chance that any of the kids would get that altruism gene. the odds of passing on any altruism genes are, obviously, higher if both parents have them. rinse, lather, and repeat for future generations within an inbred family and you can see how the evolution of altruism is made easier.

but note that it’s “sib altruism” we’re talking about here, not a broad, all-encompassing altruism towards all of mankind. inbreeding leads to insular altruistic sentiments.
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pg. 91:

“In family-structured populations…

*think: the arab world*

“…there is a direct relationship between the inbreeding process and the foundation of the groups within which social interactions take place (families). Family groups are a direct product of a single mating. To the extent that matings are between relatives, the resulting offspring arrays can be expected to be less variable. However, this direct relationship between inbreeding and the foundation of groups in family-structured population is absent in group selection in hierarchically structured populations….

*definition of a hierarchically structured population: “A population is hierarchical, if it can be divided into a certain amount of subpopulations in such a way that the set may naturally break into classes (levels).”*

“In hierarchically structured populations, interactions take place within groups (subpopulations) that include many families. The subpopulation in a hierarchically structured species is more analogous to the total population of a family-structured population, in which the total variance does increase with inbreeding. By studying inbreeding models of multifamily groups (Wade and Breden 1987), the apparent difference between kin selection and group selection concerning the prospects of altruism within groups should be resolved. The beneficial effect of inbreeding on the prospects of altruism due to individual selection should decrease as more and more families contribute to a group, so long as the offspring of families within the same group interact at random.

translation (i think): in a society which is not based upon families (a society unlike the arab world, iow), if people mate more-or-less randomly within their sub-population (say, the middle class), then there will be less “sib altruism” within that sub-population and more “broad but shallow regional blood ties” as steve sailer described it.

**you’re welcome! (^_^)

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even monkeys do it

i love primates! especially the non-human ones. (humans — meh. i can take ’em or leave ’em. (~_^) ) non-human primates are so … human sometimes! or, rather, if you watch how they behave, you can really see that we’re just a bunch o’ fur-less primates running around. (^_^) (of course, even the behaviors of beetles reminds me that we are just organic creatures, so you shouldn’t really listen to me.)

here’s some nice research on altruistic behavior (grooming!) amongst macaques in japan. it’s cool to see how the amount of grooming between relatives tapers off as the relatedness between individuals becomes more distant. from “The Monkeys of Arashiyama” [pgs. 212-13]:

“Table 1 shows the number of possible pairs and the number of grooming pairs formed, according to the relatedness of the monkeys. From this table, it is apparent that while only 6.3% of the possible number of unrelated pairs formed grooming pairs, 43.9% of the possible number of related pairs were observed to groom. Moreover, between mothers and their offspring, 85.9% of the possible number of these pairs formed grooming pairs. For the second degree of relatedness, 43.9% of the possible pairs formed grooming pairs (siblings 48.9%, grandmother-grandoffspring 9.3%). For the third degree of relatedness, 21.7% of the possible pairs formed grooming pairs. For the fourth degree of relatedness, 8.7% of the possible pairs formed grooming pairs. These results suggest that both the age-sex and the degree of relatedness between individuals strongly influenced the formation of grooming pairs.”

a little bit to the left, please. yes. right there. ahhhhhhhhhh!

previously: even plants do it and more plants playing favorites and even ROBOTS do it!

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“the selfish gene”

i recently persuaded someone of my acquaintance to read dawkins’ “The Selfish Gene,” and as i’m guessing — or, rather, hoping — that they’ll prolly want to discuss it, i’ve started re-reading it — refresh the ol’ memory (i read it several years ago now).

i also decided that i may as well babble about it here, too, since it’s right on topic! (^_^) i’m sure most or many of you have already read it, but if you haven’t, i suggest you run out (or log on to amazon) and buy it asap! (or check it out of the library!) it’s a marvelous book, even tho it has its faults (mostly because dawkins has his faults. heh — don’t we all?).

so, chapter one (i’ve got the 1989 edition, reissued in 1999): “Why are people?” i think the three most interesting points he introduces in this chapter are the individual vs. group selection debate, inclusive fitness being the reason for many altruistic behaviors, and how much genes “control” our altruistic (or not) behaviors.

the individual vs. group selection debate? i dunno — i’m about as familiar with it as, i think, a non-specialist layperson can be, but i’m really in no position to come to a conclusion about who’s right or who’s wrong here. i know that most evolutionary biologists have concluded that natural selection operates only on individuals (or, really, on genes) and not groups, but that there is a minority group (messrs. wilson, et. al.) who object.

i’m staying agnostic on the issue for now because i’m neurotic i just don’t have the knowledge base to conclude one way or another. individual selection sure makes logical sense to me, like i say, as a layperson. and i haven’t given much thought to group selection, really. but i will note that both william hamilton and george price seemed persuaded by it — or, at least, didn’t rule it out. from hamilton’s “Narrow Roads of Gene Land, Vol. 1” (this is as quoted by david sloan wilson, btw):

“A manuscript did eventually come from him [price] but what I [hamilton] found set out was not any sort of new derivation or correction of my ‘kin selection’ but rather a strange new formalism that was applicable to every kind of natural selection…. His voice was squeaky and condescending, rather guarded on the phone…. He spoke of his formula as ‘surprising for me too — quite a miracle’ … ‘Have you seen how my formula works for group selection?’ I told him, of course, no, and may have added something like: ‘So you actually believe in that do you?’ Up to this contact with Price, and indeed for some time after, I had regarded group selection as so ill-defined, so woolly in the uses made by its proponents, and so generally powerless against selection at the individual and genic levels, that the idea might as well be omitted from the toolkit of a working evolutionist….

“I am pleased to say that, amidst all else that I ought to have done and did not do, some months before he died I was on the phone telling him enthusiastically that through a ‘group-level’ extension of his formula I now had a far better understanding of group selection acting at one level or at many than I had ever had before.”

well, if it was good enough for william hamilton….
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now — inclusive fitness and how that leads to altruistic or selfish behaviors. this from dawkins relates to individuals vs. groups again [pg. 8]:

“The individual-selectionist would admit that groups do indeed die out, and that whether or not a group goes extinct may be influenced by the behavior of the individuals in that groups. He might even admit that if only the individuals in a group had the gift of foresight they could see that in the long run their own best interests lay in restraining their selfish greed, to prevent the destruction of the whole group…. But group extinction is a slow process compared with the rapid cut and thrust of individual competition. Even while the group is going slowly and inexorably downhill, selfish individuals prosper in the short term at the expense of altruists…. [E]volution is blind to the future.”

well, this is related to what i was complaining about the other day — that people have no foresight! at least not when it comes to thinking about the fate of humanity a hundred or hundreds of years into the future. but i understand — how on earth would that ever be selected for when you’ve got individuals vs. individuals in everyday life?

*sigh*
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my big complaint about dawkins is that his opinion on the nature vs. nurture debate leans too far towards the nuture side for my tastes. thus his crusade against religion (good luck with that!) — and his belief that we might be able to fight our altruism/non-altruism genes. well, yeah, maybe a bit — but dawkins really thinks such a thing would be possible [pg. 3]:

“As a corollary to these remarks about teaching, it is a fallacy — incidentally a very common one — to suppose that genetically inherited traits are by definition fixed and unmodifiable. Our genes may instruct us to be selfish, but we are not necessarily compelled to obey them all our lives. It may just be more difficult to learn altruism than it would be if we were genetically programmed to be altruistic.”

meh.

rushton, et. al., found that the heritability of altruistic behavior was something like 50% (in modern britons in the 1980s). seems like altruistic behaviors, then, like many of our personality traits and behaviors, are pretty strongly heritable. no one’s gonna change that fact that much by edumacation or culture or anything like that. if anything, the more environmental circumstances for individuals were to be equalized (either make society wonderful and easy for everybody, or make it an absolute dog-fight for everybody) the more the genetics would come into play — ironic but true.

also, whether or not individuals behave altruistically shifts (on average) depending upon with whom they are interacting — that’s the whole point of inclusive fitness! interact with a family member and an individual is likely to be pretty altruistic — interact with a stranger and eh … not so much altruism.

therefore, make a society multi-cultural and you just have to expect altruism to drop. especially in bad economic times. people can afford to be pretty altruistic when times are good. when times are bad — look out. you’re just never going to get everyone to be altruistic under such circumstances. not without some futuristic genetic engineering or something! teaching people to be altruistic ain’t gonna cut it. (of course, there’s reciprocal altruism, too, but since that’s based even more directly on “what’s in it for me?” sort-of thinking, i would think that’ll be the first to go in dire economic times.)
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btw, one of the best parts of “The Selfish Gene” is the cover! at least on the edition that i have. look! LOWERCASE letters only in the title! (~_^)

update 10/04: see also “the replicators”

(note: comments do not require an email. altruism — workin’ for this guy!)