Re: Article: Group selection, a theory whose time has come...again

Bill Morse wrote:

John Harshman wrote:


Bill Morse wrote:


John Harshman wrote:



Bill Morse wrote:



John Harshman wrote:




Bill Morse wrote:




John Harshman wrote:





Perplexed in Peoria wrote:





"John Harshman" <jharshman.diespamdie@xxxxxxxxxxx> wrote in message
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Perplexed in Peoria wrote:






"John Harshman" <jharshman.diespamdie@xxxxxxxxxxx> wrote in
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dkomo wrote:

[quoting Sterelny and Griffiths]






"Wilson argued that the trait group is a unit of selection.
Trait groups composed of altruistic animals can outcompete trait
groups of
selfish animals. This can be true even if *within every trait
group* the selfish animals are out-competing the altruistic
individuals."

Can it? How? If the selfish animals outcompete the altruistic
ones, won't altruism disappear in the group?


The trick seems to be that the trait groups don't persist all that
long,
as compared to organism lifetimes. That way you can randomly
reform trait groups (perhaps by fissioning the successful ones),
and simply from the sampling variance, you may get some trait
groups that are more altruistic than the population or
subpopulation from
which you sampled. Also, of course, some that are less
altruistic. But if the parameters are set up so that highly
altruistic groups have a big enough advantage, then the frequency
of altruism may rise in the population as a whole.

The thing is, when most people think of group selection, they are
thinking of groups that live much longer than individuals. Things
like human 'tribes'. And getting the parameters to favor the
spread of altruism in a population composed of long-lived, mostly
inbred groups (the picture most people have) is much more
difficult. Almost impossible.


Thus sounds almost sensible to me. How realistic are the model
parameters you need to make it work?


Fairly realistic, IMHO.

IIRC, there is some discussion of a working model in the Sober and
Wilson book, presumably with citations leading to more details. I
seem to recall reading some of the original trait-group papers, as
well. My current understanding of these models and the importance
that group lifetimes be short comes from those sources. Also, IIRC,
those sources contained at least one example in which the groups
persist for a time even shorter than an organism lifetime - that is,
during the life-history of the organism, one phase of its life (and
one important aspect of its survival selection) is spent in groups.

Sounds like you have to be very careful about the biological
realities here. Trait groups can come very close to being family
groups, and then we're back to kin selection. I'm not sure about
beavers, but in the average cooperative group in birds, only one
female gets to lay any eggs, and often only one male fertilizes them,
and most helpers are offspring from previous years. Further, the
helpers gain other individual benefits from being present in the
territory, among them being a chance to inherit.

So I'm interested, but cautious.

Now if we had a cooperative group of unrelated individuals in which
every member had a shot at reproduction which would be enhanced by
group success, that would be interesting.


The thought just occurred to me. Why wouldn't a monogamous pair be
such a group?


Indeed it would be. So never mind, it wouldn't be interesting. The
evolution of pairs is covered just fine by individual selection.


Arguably, monogamy could not appear by individual selection because it
would
be subject to cheaters. Quoting one J. Harshman, "If the selfish
animals outcompete the altruistic ones, won't altruism disappear in the
group?" Why doesn't this apply to monogamous couples?

Monogamy *is* subject to cheaters. Most monogamous species that have
been studied have a fair proportion of cheating. There are various
mechanisms to punish them too. It's a very interesting and complex
field, as I've said. But I see nothing that group selection is needed
for here.


I am not yet convinced. Yes of course cheating is well known in
monogamous species. But how do the mechanisms arise to control cheating
if the monogamy doesn't predate the cheating?

I don't understand this point. Monogamy could be considered a mechanism
to control promiscuity, so promiscuity must by your logic predate
monogamy.

Per Trivers, monogamy is the expected result of equal parental investment.
Where do you get this "mechanism to control promiscuity"? And it is clear
that promiscuity is ancestral and monogamy derived, unless you are
maintaining that sponges are monogamous.

I would say rather that the transitions between mating systems, in all
directions, have happened many times, so it doesn't pay much to consider
what the very first mating system was.

It would seem to me that there are very few species in which equal
parental investment is required by biology, rather than as a result of
negotiation.

And don't mechanisms to prevent
cheating indicate that the phenomenon being studied is in fact group
selection?

Why? A mechanism to control cheating is presumably advantageous to the
cheatee.

But it is presumably disadvantageous to the cheater, which remember is the
same species. It is only if both potential cheatee and potential cheater do
better if cheating is controlled that the mechanism will be selected - in
other words if the selection is operating at the level of the group (in
this case a group of two).

That doesn't follow at all. Conflicts between sexes are well known, and
as long as males and females have slightly different genomes (which of
course they generally do), both sexes can be selected separately. They
can even be selected when the sexes aren't genetically different, but it
takes a bit more work.

Note that we have wandered here from the arguments given in the
Wilson and Wilson article, but I still find it an interesting question.
Especially since monogamy occurs among many taxa, it would seem that the
prerequisites for group selection are also widespread- which would make
group selection much more feasible in principle.

*If* we allow your assumption that monogamy implies group selection, for
which I see no justification.

No, even if monogamy is simply an example of reciprocal altruism, the fact
that the mechanisms exist to control cheating means that true group
selection is possible.

It would seem to me that in order for there to be true group selection,
we would require that group advantage be contrary to individual
advantage. I see no indication of that here.

.

Relevant Pages

  • Re: Article: Group selection, a theory whose time has come...again
    ... Trait groups composed of altruistic animals can outcompete ... frequency of altruism may rise in the population as a whole. ... The thing is, when most people think of group selection, they ... Monogamy *is* subject to cheaters. ...
    (talk.origins)
  • Re: Article: Group selection, a theory whose time has come...again
    ... Trait groups composed of altruistic animals can outcompete ... frequency of altruism may rise in the population as a whole. ... The thing is, when most people think of group selection, they ... Monogamy *is* subject to cheaters. ...
    (talk.origins)
  • Re: Article: Group selection, a theory whose time has come...again
    ... Cheaters will decrease the fitness of other individuals while attempting to enhance their own, so in the end the fitness of the cheater will decrease as well, hence cheaters will be selected against by group selection. ... kin selection and reciprocal altruism models contra group selection that I "don't understand natural selection." ... Groups and Superorganisms" there is a fairly long and detailed discussion of group selection and the beaver example is used in various spots. ... Trait groups are groups of organisms, each of which feels the influence of the others with respect to some trait. ...
    (talk.origins)
  • Re: Article: Group selection, a theory whose time has come...again
    ... Trait groups composed of altruistic animals can outcompete trait ... of altruism may rise in the population as a whole. ... one important aspect of its survival selection) is spent in groups. ... Monogamy *is* subject to cheaters. ...
    (talk.origins)
  • Re: Article: Group selection, a theory whose time has come...again
    ... groups composed of altruistic animals can outcompete trait groups ... then the frequency of altruism may rise ... The thing is, when most people think of group selection, they are ... Monogamy *is* subject to cheaters. ...
    (talk.origins)
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