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

John Harshman wrote:
dkomo wrote:


John Harshman wrote:


dkomo wrote:




John Harshman wrote:




John Wilkins wrote:






Mark Isaak <eciton@xxxxxxxxxxxxx> wrote:







On Sat, 01 Dec 2007 17:10:24 +0000, John Harshman wrote:







dkomo wrote:







[I found this post by Robert Karl Stonjek over on sci.bio.evolution and
decided to repost it here because it should be of general interest.
Besides, I love to point out instances of the shortcomings of over-reductionism in evolutionary biology. -- dkomo]


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Group selection, a theory whose time has come...again

Sociobiology, the discipline founded on Darwin's theory of group
evolution, is in theoretical disarray. In a landmark article for the
December issue of the Quarterly Review of Biology, eminent evolutionary
scientists David Sloan Wilson and Edward O. Wilson usher in a new era
in evolutionary science.

"Although a high standard of morality gives but a slight or no
advantage to each individual man and his children over the other men of
the same tribe...an advancement in the standard of morality will
certainly give an immense advantage to one tribe over another."

With these words, Charles Darwin proposed an evolutionary explanation
for morality and pro-social behaviors- individuals behaving for the
good of their group, often at their own expense-that anticipated the
future discipline of Sociobiology. A century after this famous passage
was published in The Descent of Man (1871), however, Darwin's
explanation based on group selection had become taboo and has not
recovered since.

In a landmark article for The Quarterly Review of Biology, "Rethinking
the Theoretical Foundation of Sociobiology," eminent evolutionary
scientists David Sloan Wilson and Edward O. Wilson-whose book
Sociobiology:The New Synthesis brought widespread attention to the
field in 1975-call for an end to forty years of confusion and divergent
theories.

They propose a new consensus and theoretical foundation that affirms
Darwin's original conjecture and is supported by the latest biological
findings.

Wilson and Wilson trace much of the confusion in the field to the
1960's, when most evolutionists rejected "for the good of the group"
thinking and insisted that all adaptations must be explained in terms
of individual self-interest. In an even more reductionistic move, genes
were called "the fundamental unit of selection," as if this was an
argument against group selection. Scientific dogma became entrenched in
popular culture with the publication of Richard Dawkins' The Selfish
Gene (1976). Although evidence in favor of group selection began
accumulating almost immediately after its rejection, its taboo status
prevented a systematic re-evaluation of the field until now.

Based on current theory and evidence, Wilson and Wilson show that
natural selection is unequivocally a multilevel process, as Darwin
originally envisioned, and that adaptations can evolve at all levels of
the biological hierarchy, from genes to ecosystems. They conclude with
a rallying cry that paraphrases Rabbi Hillel: "Selfishness beats
altruism within groups. Altruistic groups beat selfish groups.
Everything else is commentary,"Wilson and Wilson free sociobiology to
once again pursue all lines of inquiry within its discipline.

Source: University of Chicago
http://www.physorg.com/news115476686.html

I'd have to read the article. But what group selection needs to explain
is how groups become altruistic in the face of an ingroup advantage to
selfishness, and how altruism can be maintained in groups that happen to
gain it in the face of that advantage. This has always been the central
problem of group selection, that it's necessarily a weaker force than
individual selection and that we thus have a problem explaining how it
could prosper in cases where there is conflict between levels.

There has been a great deal of research into just this problem, mostly
using game theory. I really haven't followed it enough to explain it,
so take what follows with a lick of salt. A critical piece is
"altruistic punishment," the willingness to punish someone else who steps
out of line from the group's norms, even at some personal expense. My
understanding is that once altruistic punishment arises, everything about
atruism (as we do it) is evolutionarily stable.

That maintains altruism from being subverted by cheaters. It doesn't
explain how it can arise in the first case. I think that group selection
is not always prohibited by individual selection. It's not always the
case that individual selection is stronger WRT some trait or behaviour
than group selection.


No? The explanation is generally that groups live much longer than
individuals and that individuals are much more numerous than groups,
both of which give individuals a much greater rate of innovation.


Depends on how you define the lifetime of a group. If every time a new individual is born or another one dies, it's a new group, then the lifetime of a group is on the same order as an individual lifetime.


Yes, and if you define the lifetime of a group as 10 minutes, it's
really short. But is this definition at all sensible or useful? I think
the answer is clearly "no".


I think so too.

And that applies to your definition too.

No it doesn't. So, how would you define the lifetime of a group?


From origination to extinction, generally. Now these are a bit tricky.
If a group splits into two groups, is either of them the original group?
Has the original group ceased to exist? This is of course also true for
species. But extinction is pretty simple. But if you would not agree
that your definition (a new group every time its membership changes) is
useless, we can't really discuss any more.


Why not? Even if a group is little more than a collection (set) of independent organisms, don't you find it bit troubling in your defintion of a group that each time a member dies or is born, the group's aggregate genome changes? Even the number of members changes, as does their collective phenotype. How can this be the same group?


For
one thing, it's impossible to have selection on a group that no longer
exists if there's any change in its composition.

I'm suggesting that changes in group composition affect the fitnesses of all its members. Fitness is continually varying. It is not a constant for an organism, even approximately. There are close interactions among the group members which produces group selection. The group is a self-organizing system.


If you're talking about individual fitness, how is it group selection?
You really need to explain beyond buzzwords here.


I'm looking at a "group" of living things as a superorganism. It's a complex adaptive system, defined like this:

"A Complex Adaptive System (CAS) is a dynamic network of many agents (which may represent cells, species, individuals, firms, nations) acting in parallel, constantly acting and reacting to what the other agents are doing. The control of a CAS tends to be highly dispersed and decentralized. If there is to be any coherent behavior in the system, it has to arise from competition and cooperation among the agents themselves. The overall behavior of the system is the result of a huge number of decisions made every moment by many individual agents.[1]"

--John Holland

http://en.wikipedia.org/wiki/Complex_adaptive_systems

A CAS is really cool. It combines the traditional ideas of biological evolution with the more modern ideas of emergence and self-organization. A CAS is self-organizing because it arises from the repeated application of simple rules by large numbers of subunits (members of the group in our case). Yet it also evolves because natural selection molds the rules of interaction among the subunits.

So that's *my* idea of group selection (or multilevel selection in general).


So
cheaters will arise at a much greater rate than will altruistic groups,
for example, making it unlikely for any altruistic group to last long
enough to achieve "fixation".

Not if the individuals of a group are tightly coupled. Then each individual's fitness depends on the fitnesses of the other members of the group. 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.


I'm afraid you don't understand natural selection.


I spent a lot of time studying natural selection et al and recently became disillusioned. I concluded that NeoDarwinism just doesn't have the horsepower to explain fully the complexity of life. More powerful theoretical models are needed as an extension to NeoDarwinism.

So don't conclude that because I don't automatically buy into the usual kin selection and reciprocal altruism models contra group selection that I "don't understand natural selection."


--dkomo@xxxxxxxx

.

Relevant Pages

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