Re: Species diversity through time

John Harshman wrote:

dkomo wrote:


John Harshman wrote:


dkomo wrote:




John Harshman wrote:




dkomo wrote:






John Harshman wrote:







dkomo wrote:



<snip for brevity>

Consider the state space of life. Evolution follows a trajectory through this space as a function of time. At a given t the "step" to the next point is random just as in an ordinary random walk, and it is a memoryless, Markov process because the next point depends only on the current point, again like an ordinary random walk. Every time Gould's "tape of life" is rewound and played again, a different trajectory through the state space results. That's why I say evolution is a random walk in Gould's view. Please keep in mind, this is not a view I agree with!


Please keep in mind that it's not a view Gould would have agreed with
either. Gould didn't think evolution was a random walk. He didn't think
that the next point on the typical evolutionary trajectory was random.
He knew that there was such a thing as natural selection, for example.

I was going to address the selection issue but ran out of steam. But I have just enough steam left to do it here.

Point being, selection itself *fluctuates*. That is, the environment is continually changing. Gould believed strongly in historical contingency did he not? He believed it was a major factor in evolution. If a huge comet hits the earth, that's one hell of a selection event! If there is a sudden increase in volcanic activity, which is one theory of what caused the Permian extinction, that also is a major change in selection.

Given that throughout deep time there have been many such unpredictable enviromental upheavals, evolution can't help but to be a random walk, expect maybe on very short time scales, where you could claim that if selection is fairly constant, evolution will then be approximately deterministic.


I would say, rather, that a great complexity of causes can result in
something quite like a random walk. (So can quite simple causes, if
they're chaotic -- I believe someone brought up the example of a
pseudo-random number generator.) But it's not really a random walk.

My point is that what you said above was a distortion of Gould's views.

And anyway, your apparent notion is that there is some general principle
of increasing complexity, which is nowhere in evidence.

Complexity, increasing or not, is *everywhere* in evidence.


And how is this relevant as a response to me?


There are really two important questions: (1) how did/does complexity arise in dynamical living systems, and (2) is there a general principle of increasing complexity in evolution. You seem only interested in (2) whereas I'm mainly interested in (1).


You may note that (2) is what we were actually talking about. If you
want to change the subject, at least give some warning.


My polemic above was addressing point (1). I pointed out that complexity is a continuous, neverending process in living things -- one that goes on all the time -- and that saying variation and selection is the cause of it is really not much of an explanation of it.


Of course it isn't. But is a new mechanism actually needed? Or can we
just explain it in any given case by getting into specifics?


We all agree that life is
complex. The question is whether there is a general principle of
increasing complexity.




It is a characteristic of every living thing from the simplest bacterium to the most elaborate animals. At root, what I'm saying is that you have *no* good explanation for how it came about it other than the vague "variation and selection".


You don't seem to have an explanation at all.



I do, actually, but it is a work in progress. I only got started seriously on the subject areas of emergence and self-organization in the last two months after reaching a state of utter exasperation with the explanatory ability of the received view in modern biology. The extremely myopic and reductionistic viewpoint there is never going to be able to explain fully the complexity of living things. Hence I'm in the middle of switching over to another paradigm.


So far the progress seems to consist only of latching on to a buzzword
or two.

buzz, buzz...from Camazine (see below):

"Self-organization is a process in which pattern at the global level of a system emerges solely from numerous interactions among the lower-level components of the system. Moreover, the rules specifying interactions among the system's components are executed using only local information, without reference to the global pattern."

buzz, buzz, buzz...Camazine...buzz...emergent properties:

"...emergent properties are features of a of a system that arise unexpectedly from interactions among the system's components. An emergent property cannot be understood simply by examining in isolation the properties of the system's components, but requires a consideration of the interactions among the system's components."

buzz, buzz, buzz....

Let me know when you have something. And then tell me what it is.


Or instead of waiting, you could take some initiative on your own. Here's a short reading list on the new biology:

_At Home in the Universe_, Stuart Kauffman -- good on the origins of life, and toward the back, complex fitness surfaces

_Complexity: Life at the Edge of Chaos_, Roger Lewin -- interviews with many of the main players in complex systems theory and theoretical biology; somewhat dated though

_Introduction to Artificial Life_, Christoph Adami -- excellent chapters on information theory as it relates to living organisms

_Self-Organization in Biological Systems_, Scott Camazine -- excellent 1st part of the book is called "Part I. Introduction to Biological Self-Organization" and has chapters like "What is Self-Organization", "Characteristics of Self-Organizing Systems", "Why Self-Organization?",
"Misconceptions about Self-Organization"

pause for thought...why *does* life self-organize? Why doesn't life just allow evolution to construct it piece by piece using selection and variation like a stone mason builds a stone wall one odd shaped stone at a time, carefully selecting each stone to fit the next place in the wall? After all, walls don't self-organize. Yeah?


--dkomo@xxxxxxxx





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Relevant Pages

  • Re: Species diversity through time
    ... again like an ordinary random walk. ... Gould didn't think evolution was a random walk. ... He knew that there was such a thing as natural selection, ... of increasing complexity, ...
    (talk.origins)
  • Re: Species diversity through time
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  • Re: Species diversity through time
    ... Gould didn't think evolution was a random walk. ... He knew that there was such a thing as natural selection, ... of increasing complexity, ... explanatory ability of the received view in modern biology. ...
    (talk.origins)
  • Re: Species diversity through time
    ... At a given t the "step" to the next point is random just as in an ordinary random walk, and it is a memoryless, Markov process because the next point depends only on the current point, again like an ordinary random walk. ... That's why I say evolution is a random walk in Gould's view. ... He knew that there was such a thing as natural selection, ... of increasing complexity, ...
    (talk.origins)
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