Selection, Reproductive rate, and Karrying Kapacity.
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Selection, Reproductive rate, and Karrying Kapacity.
 
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All,
Here are some comments on various comments. I succumb, reluctantly, to the community norm about caps.
[grumble, grumble]
Glen Said ====>
The idea of expansion and contraction is
interesting: rapid expansion of populations
(when selection is relaxed) vs. rapid contraction
of populations (when selection is intensified).
The human population went indeed through a
phase of rapid expansion in the last decades while
natural selection was released through cultural
and technological progress.
Seed Magazine has an article about human
evolution and relaxed selection, too
Nick Replies ===>
I think this is a confusion between carrying capacity and selection. When, for some reason, carrying capacity is increased, the whole population can expand, but this does not stop selection. It may change the nature of selection from tracking how well individuals can make use of limited resources to how fast they can reproduce when times are flush, but there is no reason to think that raising the carrying capacity should "relax" selection.
Russell Wrote ===>
Any extinction event is a collapse of the food web. And selection only
proceeds by means of extinction. So I'm not really quite sure what
you're trying to nuance here.
Nick Replies ===>
OK. Here is where we disagree, I think. Let's worry this a bit, before we talk about anything else, because it seems absolutely central: When talking about selection, at what level of organization are we speaking? Gene, individual, small group, "deme", species, ecosystem? etc. I grew up under the influence of George Williams who argued that no entity above the individual could serve as a level of selection and of Richard Dawkins, who argued that no entity above the level of the gene could serve as a level of selection. So, in my world, species level selection is not a powerful cause of evolution. Indeed, on some definitions, species, by definition, cannot compete. Now, in the last decade, I have thrown off Williams' shackles and started to talk about selection at the level of the small group. And, indeed, I do know that some others have started talking about species-level selection. But species level selection has not become the received view, has it???? If not, the statement above must be EXTREMELY [whoops, _extremely_] controversial.
Let's pause here and see what others say.
Nick Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Selection, Reproductive rate, and Karrying Kapacity.
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No. That wasn't me that said that. It was Jochen. I added the content-less post quoting Ehrlich. Thus spake Nicholas Thompson circa 10/13/2008 11:18 AM: > Glen Said ====> > > The idea of expansion and contraction is interesting: rapid expansion > of populations (when selection is relaxed) vs. rapid contraction of > populations (when selection is intensified). > > The human population went indeed through a phase of rapid expansion > in the last decades while natural selection was released through > cultural and technological progress. > > Seed Magazine has an article about human evolution and relaxed > selection, too > http://www.seedmagazine.com/news/2008/10/how_we_evolve_1.php <=== > > Nick Replies ===> > > I think this is a confusion between carrying capacity and selection. > When, for some reason, carrying capacity is increased, the whole > population can expand, but this does not stop selection. It may > change the nature of selection from tracking how well individuals can > make use of limited resources to how fast they can reproduce when > times are flush, but there is no reason to think that raising the > carrying capacity should "relax" selection. -- glen e. p. ropella, 971-219-3846, http://tempusdictum.com ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Selection, Reproductive rate, and Karrying Kapacity.
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In reply to this post by Nick Thompson
I agree with most of Nick’s hesitations (except re: all
caps…. :-)) Population expansion would increase
the variety of individuals to be selected from, though. I
think that was the idea behind Terry Deacon’s theory, still with variation
being random and constant, and using the same old tautology that change is
caused by what survives. That there are several levels
of (mostly unexplained) organization and the need for selection to somehow
differentiate between them, and to do so differently for every organism in the
environment, has always been a problem for me in seeing selection as the
primary hand of ‘design’. When I build things that way
it never works… Still, if there are times of great
variety in emerging designs and generous environmental capacities for all to flourish,
one of the newbies may be the one that survives when the tide turns to drought
and famine… That’s sure how it works in economies, and
ecologies are indeed natural economies. One thing I don’t see addressed by changing selective
pressures to vary rates of evolution is the possibility of, and apparent need
for, ‘mutations’ that have low rates of destroying the whole
organism. Punctuated equilibrium seems to imply that there
are rare periods when the success rate of diverse interrelated mutations is a
lot higher than the rest of the time. That there is some kind
of switch that turns whole system malleability on and off. If
you just had a little greater likelihood of mutations at the periphery of the
genome’s design, whatever that is, in preference to it’s central
structures, it would produce a lot more variation in functional design in
proportion to dysfunctional design. In that
plankton paper of mine I also broadly speculate on particular mechanisms for
that. That seems to be the same issue Kirschner and Gerhart are
getting at when subtitling their book “resolving Darwin’s dilemma”
and by some of the other EvoDevo models I keep hearing about where variation
trees rather than random disruptions are the key to inventing new things that
work . Phil From:
[hidden email] [mailto:[hidden email]] On Behalf Of Nicholas
Thompson All, Here are
some comments on various comments. I succumb, reluctantly, to
the community norm about caps. [grumble,
grumble] Glen
Said ====> The idea of
expansion and contraction is interesting:
rapid expansion of populations (when
selection is relaxed) vs. rapid contraction of
populations (when selection is intensified). The human
population went indeed through a phase of
rapid expansion in the last decades while natural
selection was released through cultural and technological
progress. Seed
Magazine has an article about human evolution
and relaxed selection, too Nick
Replies ===> I think
this is a confusion between carrying capacity and selection. When, for
some reason, carrying capacity is increased, the whole population can expand,
but this does not stop selection. It may change the nature of selection
from tracking how well individuals can make use of limited resources to how
fast they can reproduce when times are flush, but there is no reason to think
that raising the carrying capacity should "relax" selection. Russell
Wrote ===> Any
extinction event is a collapse of the food web. And selection only proceeds by
means of extinction. So I'm not really quite sure what you're
trying to nuance here. Nick
Replies ===> OK.
Here is where we disagree, I think. Let's worry this a bit, before we
talk about anything else, because it seems absolutely central: When
talking about selection, at what level of organization are we speaking?
Gene, individual, small group, "deme", species, ecosystem?
etc. I grew up under the influence of George Williams who argued that no
entity above the individual could serve as a level of selection and of
Richard Dawkins, who argued that no entity above the level of the gene could
serve as a level of selection. So, in my world, species level selection
is not a powerful cause of evolution. Indeed, on some definitions,
species, by definition, cannot compete. Now, in the last decade, I have
thrown off Williams' shackles and started to talk about selection at the level
of the small group. And, indeed, I do know that some others have started
talking about species-level selection. But species level selection
has not become the received view, has it???? If not, the statement above
must be EXTREMELY [whoops, _extremely_] controversial. Let's pause
here and see what others say. Nick Nicholas
S. Thompson Emeritus
Professor of Psychology and Ethology, Clark
University ([hidden email]) ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Selection, Reproductive rate, and Karrying Kapacity.
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In reply to this post by Nick Thompson
One of my favorite books of the year is David Sloan Wilson's Evolution for Everyone. Wilson has been arguing for multi-level selection for quite a while -- and as far as I'm concerned he makes very good points.
The fundamental insight is that everything is both a group and an individual. And hence virtually anything can evolve at the individual level -- even if it's a group. Wilson likes talking about religions (or religious groups united by religious practices) as an example of a group that competes evolutionarily. He argues that religious that promote hard work, support of fellow members of one's religious community, etc. tend to succeed. He also tells the story of the experient in which groups of hens were allowed to evolve. It was done in two ways. 1. Start with (say) a dozen cages, each with a certain number of hens. At the end of a given time, the best egg-layer in each cage were bred to create a second generaation of cages. Continue for a certain number of generations. 2. Start the same way, but after each generation, breed the best cage, regardless of how its individual members performed. Continue for a certain number of generations. The result: breeding cages was much more successful than breeding individuals. In this case it turns out that breeding individuals produced macho hens who pecked each other to death. Breeding cages produced cooperative hens who lived happily with each other and produced lots of eggs. The larger lesson is that groups often embody structures that support the group's success. To enable those structures the group needs members who play various roles. Simply selecting the most productive members of a group and rewarding them breaks down the group structure. -- Russ On Mon, Oct 13, 2008 at 11:18 AM, Nicholas Thompson <[hidden email]> wrote:
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Re: Selection, Reproductive rate, and Karrying Kapacity.
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In reply to this post by Nick Thompson
Russ,
Yes. I agree. However, the problem with the chicken experiment is that the chickens in the cages were SISTERS. Not a problem, obviously, for the purposes of egg production, but for peace and quiet of group selection theorists, not so great.
You could double the readership my paper on this subject by going to http://www.behavior.org/journals_bp/index.cfm?page=http%3A//www.behavior.org/journals_bp/BP_welcome.cfm.
Behavior and Philosophy , 28, 83-101 (2000). © 2000 Cambridge Center for Behavioral Studies Take care,Nick Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Selection, Reproductive rate, and Karrying Kapacity.
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In reply to this post by Nick Thompson
On Mon, Oct 13, 2008 at 12:18:11PM -0600, Nicholas Thompson wrote:
> > Russell Wrote ===> > > Any extinction event is a collapse of the food web. And selection only > proceeds by means of extinction. So I'm not really quite sure what > you're trying to nuance here. > > Nick Replies ===> > > OK. Here is where we disagree, I think. Let's worry this a bit, before we talk about anything else, because it seems absolutely central: When talking about selection, at what level of organization are we speaking? Gene, individual, small group, "deme", species, ecosystem? etc. I grew up under the influence of George Williams who argued that no entity above the individual could serve as a level of selection and of Richard Dawkins, who argued that no entity above the level of the gene could serve as a level of selection. So, in my world, species level selection is not a powerful cause of evolution. Indeed, on some definitions, species, by definition, cannot compete. Now, in the last decade, I have thrown off Williams' shackles and started to talk about selection at the level of the small group. And, indeed, I do know that some others have started talking about species-level selection. But species level selection has not become the received view, has it???? If no! > t, the statement above must be EXTREMELY [whoops, _extremely_] controversial. > > Let's pause here and see what others say. > I don't think there is disagreement, more a difference in perspective. You are focussing on short term evolutionary change, aka microevolution. I'm more interested in long term evolutionary change, or macro evolution, which is composed of speciation and extinctions. Of course evolution must proceed via changing genetic frequencies, as otherwise how will a single mutation come to dominate an entire gene pool. However, once established, a given haplotype will rarely become extinct in a sexually reproducing population unless that population is very small, and that will only happen in a genetic bottleneck or true species extinction. Nothing of what I said earlier has anything to do with the group selection debate (although I do tend to think, along with EO Wilson, that group selection effects exist). It just comes from think of the mechanics of evolution at an ecosystem scale, where species are the individual components of the ecosystem. In this view, a dramatic change in behaviour of a species (say radical alteration of prey species, or successful defence against some previous predator) that is not in response to a change elsewhere in the food web, would really constitute a new species, even if technically the new and old versions could still interbreed. -- ---------------------------------------------------------------------------- A/Prof Russell Standish Phone 0425 253119 (mobile) Mathematics UNSW SYDNEY 2052 [hidden email] Australia http://www.hpcoders.com.au ---------------------------------------------------------------------------- ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Selection, Reproductive rate, and Karrying Kapacity.
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In reply to this post by Russ Abbott
Russ, That’s a good example about the difference between
breeding for the best bird vs. the best bird environment, but they don’t immediately
seem to address whether variation is developmental or random.
It’s tricky to find the hard evidence, but I don’t know of
anyone saying they could show statistically that random variation would be
constructive either. My hint is that the organizational
processes we can observe the workings of generally do exhibit developmental
variation, like we use in any programming or other design process. Once you think of the first part in the design, the process that
seems to work better for people is adding a second related part, *if the
first seemed to work*, and that way extending variations from prior
variations experimentally, rather than randomly. It takes
some effort to imagine how genetic variation could be ‘tree like’
instead of helter skelter… but there a number of ways. What
you need is for competitive advantage to multiply related variations.
In any case individual organism growth and development is
clearly a branching process, and speciation seems to clearly be an extension of
a prior branching process. Maybe speciation occurs by a branching
process too. In speciation the form of the organism appears
to extend its developmental trees as whole, all at once, something that a tree
like variation process could do and a random variation process very likely not.
So that’s what I think would be sensible to look for. Besides, tree-like development could do one thing that random
variation can’t, produce developmental step changes that begin and end.
That’s what is apparently displayed by my little plankton. I’d
really love to have the $’s to do a photo animation of how the smooth to
then bulgy shapes on it’s shell changed through the dips and turns of it’s
dramatic changes in size from one to another stable form. Phil From:
[hidden email] [mailto:[hidden email]] On Behalf Of Russ
Abbott One of my favorite books of the
year is David Sloan Wilson's Evolution for Everyone. Wilson has been
arguing for multi-level selection for quite a while -- and as far as I'm
concerned he makes very good points. On Mon, Oct 13, 2008 at 11:18 AM, Nicholas Thompson <[hidden email]>
wrote: All, Here are some comments on various comments. I
succumb, reluctantly, to the community norm about caps. [grumble, grumble] Glen Said ====> The idea of expansion and contraction is interesting: rapid expansion of populations (when selection is relaxed) vs. rapid contraction of populations (when selection is intensified). The human population went indeed through a phase of rapid expansion in the last decades while natural selection was released through cultural and technological progress. Seed Magazine has an article about human evolution and relaxed selection, too Nick Replies ===> I think this is a confusion between carrying capacity and
selection. When, for some reason, carrying capacity is increased, the
whole population can expand, but this does not stop selection. It may
change the nature of selection from tracking how well individuals can make use
of limited resources to how fast they can reproduce when times are flush, but
there is no reason to think that raising the carrying capacity should
"relax" selection. Russell Wrote ===> Any extinction event is a collapse of the food web. And
selection only proceeds by means of extinction. So I'm not really quite
sure what you're trying to nuance here. Nick Replies ===> OK. Here is where we disagree, I think. Let's
worry this a bit, before we talk about anything else, because it seems
absolutely central: When talking about selection, at what level of
organization are we speaking? Gene, individual, small group,
"deme", species, ecosystem? etc. I grew up under the
influence of George Williams who argued that no entity above the individual
could serve as a level of selection and of Richard Dawkins, who argued
that no entity above the level of the gene could serve as a level of
selection. So, in my world, species level selection is not a powerful
cause of evolution. Indeed, on some definitions, species, by
definition, cannot compete. Now, in the last decade, I have thrown off
Williams' shackles and started to talk about selection at the level of the
small group. And, indeed, I do know that some others have started talking
about species-level selection. But species level selection has not
become the received view, has it???? If not, the statement above must be
EXTREMELY [whoops, _extremely_] controversial. Let's pause here and see what others say. Nick Nicholas S. Thompson Emeritus Professor of Psychology and Ethology, Clark University ([hidden email])
============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Selection, Reproductive rate, and Karrying Kapacity.
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In reply to this post by Russell Standish
Russ & Nick,
Regarding multilevel selection, aren't there multi-level systems involved? Certainly a change in cell behavior affects the organism, and the local pack, and larger population, and the local ecology too. But you also have reverse effects in that the larger scale orders greatly alter what each lower order differences will make a difference. Then there's the interesting aspect that some kinds of complex systems overlap in lots of ways, like complexly varied ecosystems with many intersecting levels, and so a simple hierarchy is not what is operating either. What can, if you follow it through, straighten all that out is considering systems as individual exploratory networks. Then you can still have independent ones that overlap and they still work fine, and all of them can have a role in mediating selection for all the others. Phil Henshaw ¸¸¸¸.·´ ¯ `·.¸¸¸¸ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 680 Ft. Washington Ave NY NY 10040 tel: 212-795-4844 e-mail: [hidden email] explorations: www.synapse9.com "it's not finding what people say interesting, but finding the interest in what they say" ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
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