well this sounds familiar…

a very kind reader points me to a fairly newly published book (pub. last month) titled Our Political Nature: The Evolutionary Origins of What Divides Us by avi tuschman (thank you, very kind reader! (^_^) )

the very kind reader thought i might be interested in the book since it’s got sections on inbreeding and outbreeding … and altruism. yes, indeed! that’s right up my alley!

i’ve only glanced through the book, but this caught my eye … sounds vaguely familiar [from chapter 10]:

“Inbreeding Increases Altruism

“There’s another potential positive-feedback mechanism that promotes inbreeding in animal populations: inbreeding can increase altruism. Altruism is the force that causes an individual to reduce his or her own fitness while increasing the fitness of another. But what’s the connection to mate choice?

“Inbreeding raises the genetic relatedness of the members of the group. Since inbreeders share a higher percentage of their genes with one another, they act less selfishly toward one another. By helping closely related individuals, inbreeders are helping to propagate copies of their own genes. Chapter 19 explains in greater detail this particular phenomenon, which is called ‘kin selection.’

“If specific alleles associated with altruism exist in (or mutate into) a population, then inbreeding can increase the frequency of these ‘altruistic’ alleles until they are ‘fixed’ in the population; that is, they can become permanent, contingent on continued inbreeding.

“In a random mating system, in contrast, altruism is likely to be lower because individuals share fewer genes in common with each other. In an outbred population, two nonrelatives may reproduce. Half of their offspring’s DNA would come from the mother, and half from the unrelated father. Among inbreeders, however, parents already share a proportion of their DNA with one another. Therefore, the inbred offspring have *more* than half of each parent’s genes. The longer a population’s history of continuous inbreeding, the higher the genetic overlap becomes. Having a child that shares more than 50 percent of one’s DNA is an easy way for a parent to increase the propagation of its genes, and therefore to gain greater fitness — without even expending any additional reproductive effort.

“Although sustained inbreeding in a human population can increase altruism among the in-group, it can also *decrease* altruism toward out-groups. This hostility may particularly occur when colonies of inbreeders live side by side but do not outbreed. Separation by a reproductive boundary would entail a sharp drop in genetic relatedness between the two groups. So altruism would be high within the groups but very low between them.”

(~_^)

like i said, i’ve only glanced through the book, but i couldn’t see anywhere where mr. tuschman connects inbreeding or outbreeding with family types. or that long-term mating patterns and their downstream effects on social structures (like on family types) likely influence selection within populations.

still, looks like a very interesting book! i shall definitely be having a read of it. (^_^)
_____

edit: from chapter 19:

“Yet regardless of political orientation, close family members tend both to behave more altruistically toward each other than toward distant kin and to treat distant kin better than non-kin. When we translate Hamilton’s Rule from biology into the language of politics, kin-selection altruism toward close kin becomes ‘nepotism’ and the preferential treatment of distant kin becomes ‘tribalism.'”

_____

see also: OurPoliticalNature.com

previously: practically everything on the blog and mating patterns, family types, social structures, and selection pressures

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

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6 Comments

  1. “inbreeding can increase altruism. Altruism is the force that causes an individual to reduce his or her own fitness while increasing the fitness of another. But what’s the connection to mate choice?…In a random mating system, in contrast, altruism is likely to be lower because individuals share fewer genes in common with each other”

    This makes sense in itself plus i think it illustrates the mechanism behind the pullme-pushyou idea.

    Altruism to close kin implies not-altruism to non, or more distant kin i.e. amoral familialism – if individuals within a population always give a potential job offer to a nephew then they always *don’t* give the job to a non-nephew – so the effect of higher altruism (scientific definition) at the extended family level might mean less *net* altruism at larger scales.

    Say you have a population of 1000 divided into 10 inbred extended families of 100 each then all those 1000 may have a lot of altruism genes and the level of altruism *within* each extended family may be high but the *net* altruism within the total population is low because for each individual within the population the pm-py calculation is + (members of extended family) – (everyone else).

    So numerically if the altruism genes in that population were given a strength of 2 then for each individual in the total population the *net* altruism score would be +200 (for the 100 members of their extended family) -1800 (for the other 900 in the total population) for a net score of -1600. If the population outbreeds among themselves so they become less strongly related to the 100 in their extended families but more strongly related to the other 900 then even if that process leads to the strength of their altruism genes dropping to 1 then their *net* pm-py score might be somewhere between +1000 (equally altruistic to everyone) to + 100 (diluted extended family) – 900 (everyone else).

    nb I think there is also a second possibility which is that altruism genes trigger in proportion to recognition of self so that inbreeding (if it leads to stronger family resemblance through linkage effects) simply makes those altruism genes trigger more (and by extension not-self, non-altruism to trigger more also).

    nb2 @hubchik could you remind me the name of that very peaceable bunch you mentioned in a post who live somewhere around Indonesia: sati, seti, sutil or something?

    Reply

  2. looks like tightly inbreeding groups are almost a weak form of species, not separated by reproductive barrier of course but start to exhibit behaviors vs outgroups halfway between intra and extra specific competition/cooperation. So the transition between in-species behavior and out-species behavior is not as sharp as reproductive barrier may imply….
    I wonder if this is the case also on the other side of the reproductive barrier, i.e. more tendency for slight altruistic behavior to closest species, no altruism altogether for distant species, and actively malicious behavior on very distant species (ie decreasing fitness of other, even at a small price of our own fitness). It seems roughly the case, with current psychological explanation liked to anthropomorphisation, or level of intelligence….but this last one is obviously false, people have much more sympathy for a small furry mamal than a crow, a mantis shrimp or an octopus….

    Reply

  3. @grey – “Altruism to close kin implies not-altruism to non, or more distant kin i.e. amoral familialism – if individuals within a population always give a potential job offer to a nephew then they always *don’t* give the job to a non-nephew – so the effect of higher altruism (scientific definition) at the extended family level might mean less *net* altruism at larger scales.

    yup!

    @grey – “@hubchik could you remind me the name of that very peaceable bunch you mentioned in a post who live somewhere around Indonesia: sati, seti, sutil or something?”

    the semai! (^_^) one of the peaceful peoples (there are others — i need to learn more about those — some kind reader pointed out this website to me a while back — thank you, kind reader, whoever you were!).

    Reply

  4. @kai – “looks like tightly inbreeding groups are almost a weak form of species, not separated by reproductive barrier of course but start to exhibit behaviors vs outgroups halfway between intra and extra specific”

    yes, i think so. almost a weak form. and the more tightly inbred (eg. the arabs), the more they see outgroups as really outgroups (which they are!).

    Reply

  5. Let’s hope there is something essentially new in his book. It would be a shame if all he did was to read this blog, edit it a little and pass it off as his own bright ideas.

    Reply

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