Re: Perpetually Perplexed

From: Joe Felsenstein (joe_at_removethispart.gs.washington.edu)
Date: 02/01/05 

Date: Tue, 1 Feb 2005 14:38:33 -0500 (EST)

In article <csormi$g19$1@darwin.ediacara.org>,
Guy Hoelzer <hoelzer@unr.edu> wrote:
>in article csjdvd$1p8i$1@darwin.ediacara.org, Joe Felsenstein at
>joe@removethispart.gs.washington.edu wrote on 1/18/05 8:37 AM:
>> OK, yes, I disagree with Guy. Hamilton's argument uses the quantity
>> r for the average degree of relationship between the altruist and the
>> recipients. The altruist can be simply being nice to the neighbors,
>> who happen to partly be its relatives. If, say, the neighbors were
>> half of them first cousins of the altruist then the appropriate
>> value of r is (1/2)x(1/16) where 1/16 is the r value for cousins.
>> This adjustment of r (the factor of 1/2) above takes care of the
>> dispensing of altruism to some non-relatives.
>>
>> There is no assumption in Hamilton's work that the altruist recognizes
>> kin. This is a common misconception about the kin selection argument.
>> One does not need to adjust Hamilton's condition for altruism "not being
>> graded" (in Guy's terminology). The calculation of the quantity r takes
>> care of it.
>
>I don't know whether you had a chance to read the entirety of my post from
>which the quote above was taken, but I would very much like to get your
>response to my argument (as opposed to my naked conclusion). I appreciate
>the argument you provide above as a mean-field approximation to the problem.
>If the organism's altruism is expressed to a particular degree in all social
>interactions (b and c are invariant for all social interactions), then
>Hamilton's Rule would hold if r is calculated as the average of all social
>interaction weighted by the frequencies of interactions with individuals of
>differing relatedness to the actor. However, the restriction on holding b
>and c constant was certainly not part of many kin selection arguments made
>by Hamilton (and consider Haldane's famous presaging statement), and it is
>not the assumption in most of the empirical kin selection literature. For
>example, kin selection is most often said to be supported by evidence that
>altruism is preferentially aimed toward close kin, and Hamilton agreed with
>this perception. He (and I) agreed with your position that kin recognition
>and perfectly graded altruism were not necessary for kin selection to favor
>the spread of altruism, but that is a different issue from the precise
>tipping point prediction embodied by Hamilton's Rule.

(Sorry for the slow response, but now there is a pause in the controversying
and that enables me to respond to some of the serious points you have made).
I think Hamilton's argument works either way, and is not made less exact
by having or not having what you call "graded" altruism. It is just a
matter of calculating the quantity r in each case.

Hamilton's argument certainly predicts that any genetic variation that
focusses the altruism on kin would be selected, provided that it does so
effectively enough. But that seems to me to be a subsidiary point. People
often assume that Hamilton's argument is that altruism evolves only when
focussed on kin, and that is not his argument.

>In sum, I agree that a mean field approximate model can be constructed that
>works, and which does not require perfectly graded (by relatedness)
>altruism. However, I would disagree if you are arguing that this is the
>only, or even the primary, model described by Hamilton. He, and the army of
>empiricists who followed him, was largely interested in kin-targeted
>altruism, whether or not kin recognition was involved. Under these
>conditions, the strength of the correlation between relatedness and
>expressed altruism affects the tipping point, which is what Hamilton's Rule
>aims to pinpoint. Where is the problem with this reasoning?

I think that in his original argument he simply used r without
specifying that its value was an outcome of kin-targeting. It might or
might not be. And his argument is no more approximate when there is
no kin-targeting. Sure, he and subsequent workers were very interested in
possible cases of kin-targeting, as that would make r larger. 

-- 
Joe Felsenstein         joe@removethispart.gs.washington.edu
 Department of Genome Sciences and Department of Biology,
 University of Washington, Box 357730, Seattle, WA 98195-7730 USA

Relevant Pages

  • Re: OOL I - Manifesto and metatheory
    ... micro-ecosystem in order for natural selection to result in such ... This argument has nothing to do with altruism. ... >> All that is required for kin selection to operate is that the actor ... kin altruism in simple chemical replicators would usually ...
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  • Re: Kin altruism
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  • Re: Hamiltons Rule: light at the end of a LONG tunnel?
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  • Re: Perpetually Perplexed
    ... This is a common misconception about the kin ... If the organism's altruism is expressed ... > invariant for all social interactions), ... > holding b and c constant was certainly not part of many kin selection ...
    (sci.bio.evolution)
  • Re: Kin altruism
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