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Topic: Macroevolution redefined in terms of evolvability
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Jack Foster
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Member # 79
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posted 04. September 2003 00:31
I've always thought that speciation was a poor dividing line betweeen micro- and macro-evolution; it's arbitrary. It's certainly easy to think of better alternatives: efficiency/complexity, or high probability/low probability.
Another potential distinction between these types of evolution can be expressed in terms of evolvability. Evolvabilty is the capacity for an evolutionary system to generate adaptation. Evolvability lives on the variation side of the evolutionary ledger (in the form of variability), and can be viewed as an internal property of the population of interest. I look at it as the relationship between genotype space and fitness space (of course through phenotype space).
Macroevolution can be viewed as the variation-driven (invention-driven) increases in the evolvability of an evolutionary system and the corresponding expansion of phenotype space and fitness terrain of the system; the evolution of evolvability. Microevolution can be viewed as selection-driven movement across the fitness terrain . . . an external property.
Microevolution is the exercise of the evolvability of a system. Macroevolution is the evolutionary increase of that evolvability.
Evolvability does not evolve in man-made evolutionary systems; it exists at some fixed level as a quality of the system. Biological evolution is different because of the ability of biological evolvability to evolve. This is why macro-evolution has been difficult to demonstrate via "dry" systems.
Thoughts anyone?
[ 04. September 2003, 00:59: Message edited by: Jack Foster ]
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gedanken
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posted 04. September 2003 01:21
I completely agree that “speciation” would be an arbitrary dividing line between microevolution and macroevolution. For example I’ve heard discussion among biologists where different definitions of species were used, and the same event was thus classified as a speciation event or not so classified depending on the definition chosen. The choice of definition may in some circumstances be arbitrary thus any dependent distinction would also.
But as I understand it (not being a biologist) macroevolution and microevolution are different methods of studying biological evolutionary effects. Thus the concept of a “dividing line” is itself a mistaken concept. For example any given evolutionary event is not categorized as “macro” or “micro” – rather the method used to study the event is what is categorized under those headings.
And of course there is a preponderance of speciation events studied in the method that uses “macro” scale view – that of the overall fossil record for example – thus the reason that many have become confused as to the scientific meaning of those terms.
So I agree, not only is the boundary arbitrary, it really doesn’t exist. (An implication is that there is no boundary or “line in the sand” across which evolutionary change crosses or any basis for an argument that evolutionary change cannot cross such a boundary.)
But I don’t understand the issues of mechanism brought up, as those mechanisms are certainly thought to be present in evolution at all levels. Once again the study is one of perspective rather than underlying mechanism – however perspective may change the focus of mechanism being most extensively studied!
An interesting case to consider it the change in “evolvability” that the HIV virus responsible for AIDS has undergone. That virus group seems to have evolved a new level and rate of change, within my lifetime, and has been studied I assume from “microevolutionary” perspective.
[ 04. September 2003, 01:57: Message edited by: gedanken ]
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Jack Foster
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posted 04. September 2003 13:35
quote:
gedanken: And of course there is a preponderance of speciation events studied in the method that uses "macro" scale view – that of the overall fossil record for example – thus the reason that many have become confused as to the scientific meaning of those terms.
There is no one specific "scientific meaning" for macroevolution (or microevolution), as far as I know. (Who is it that would determine the official "scientific meaning" of such words, anyway?!) People including Scientists use the term in different ways. Consensus for the dividing line seems to be at the level of species, but as you know, even species is an ambiguous term! I've been reading and debating this stuff for five years, and this is the first time I've heard your definition! Since the term is so ambiguous, I thought I would add to the mud by throwing a few more potential definitions into the ring! Perhaps some of us can agree upon which definition is the most useful.
Some people deny that there's a difference between micro- and macro-evolution, but this usually boils down to a semantics argument. They mean that RM & NS are responsible for both, and perhaps that's so. But it's hard not to see the difference between the simple selection of pre-existing morphs and the revolutionary inventions of our evolutionary history like meiosis and multicellularity! Inventions cannot come about by accumulated micro-evolution; assuming naturalism, they must arise as a product of chance. Selection cannot act until there is some basic capability or function upon which to act.
So every single one of life's multitude of inventions must come about as a product of chance. And that's another distinction between macro- and micro-: macro-evolution is invention (and therefore independent of selection), and micro-evolution is response to environment without invention (and therefore independent of new variation). And of course there are shades of gray.
I realize that this distinction is a slightly different distinction than the evolvability distinction. Invention can occur in systems with fixed evolvability. (I think . . . though it could be argued that new invention requires genome space, and larger genomes are more evolvable than smaller ones.)
macro, invention, variation-driven, internal, low-probability, "quantum" leaps, complexity, enhanced evolvability, non-Darwinian
vs.
micro, tuning, selection-driven, external, hi-probability, gradualist, efficiency, fixed evolvability, Darwinian
[ 04. September 2003, 13:49: Message edited by: Jack Foster ]
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gedanken
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posted 04. September 2003 15:07
Here is a link that somewhat disagrees with the way I put it. (Sorry about it's source, I don't mean to imply anything by the particular site.)
But even in distinguishing changes at level of "gene pool" and changes "which are significant enough that, over time, the newer organisms would be considered an entirely new species", this does not indicate that the distinction is among individual events but in how they are examined. I believe that what I presented is correct, but that may not invalidate the distinction as relating to species differentiation. That site certainly support's Jack's contention that the definition is arbitrary!
quote:
So every single one of life's multitude of inventions must come about as a product of chance. And that's another distinction between macro- and micro-: macro-evolution is invention (and therefore independent of selection), and micro-evolution is response to environment without invention (and therefore independent of new variation). And of course there are shades of gray.
Did you intend to propose this as a definition (e.g. defining "micro-evolution" as non-inventive)? Or did you mean to argue this as a further observation about cases that match a different definition of the micro/macro distinction you are proposing?
And quote:
Inventions cannot come about by accumulated micro-evolution; assuming naturalism, they must arise as a product of chance. Selection cannot act until there is some basic capability or function upon which to act.
Once again were you meaning to define microevolution as not involving both "chance" such as mutation, and involving selection? Or are you stating these as observations about the change that occurs according to an independently given definition of micro/macro evolution distinctions?
And in first quote "macro-evolution is invention (and therefore independent of selection)": Do you mean to state that macro-evolution is independent of "selection", e.g. that macroevolutionary processes are not dependent on selection for their operation and understanding?
[ 04. September 2003, 15:31: Message edited by: gedanken ]
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RBH
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posted 04. September 2003 15:49
I'm going to register a complaint: Jack S started this thread during a time when I have zero time to participate!
RBH
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Jack Foster
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posted 04. September 2003 20:13
Here from . . . TalkOrigins of all places! A pretty good history of the words, though obviously I disagree with TO's conclusions. I searched the Scientific Literature as well. Most scientific sources use the terms without defining them. One source defined macroevolution as "phylogenetic biology" and defined microevolution as "population genetics", which is more or less consistent with the species line definition.
If evolutionists feel that there's no difference between micro and macroevolution, then maybe we should look for new definitions where there clearly IS a difference. I've actually proposed several candidates: evolvability, invention/fine-tuning, efficiency/complexity, variation-driven/selection-driven. . .
It might be said that Darwinism requires a theory of variation. This is why the synthesis between Darwinism and Mendelian genetics proved so powerful. It appears more focus is being placed upon the variation side of Darwin's algorithm now by some within the evolutionary sciences. Since Wagner and Altenberg, we have a new focus on variability and evolvability. And some in the evo-devo field are talking about variational biases as well.
Onto your questions:
quote:
Did you intend to propose this as a definition (e.g. defining "micro-evolution" as non-inventive)? Or did you mean to argue this as a further observation about cases that match a different definition of the micro/macro distinction you are proposing?
I'm proposing that macroevolution and microevolution be redefined in a way that is useful. I see broadscale phyologenetic evolution as distinctly different from the microevolution of population genetics. I'm describing several ways in which the two concepts are different.
quote:
And in first quote "macro-evolution is invention (and therefore independent of selection)": Do you mean to state that macro-evolution is independent of "selection", e.g. that macroevolutionary processes are not dependent on selection for their operation and understanding?
New useful inventions are indeed selected. But selection cannot explain new useful inventions.
Note to RBH: What?? You can walk through the door, but you can't talk a bit? ![[Wink]](wink.gif)
[ 04. September 2003, 20:17: Message edited by: Jack Foster ]
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gedanken
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posted 04. September 2003 21:14
quote:
I'm proposing that macroevolution and microevolution be redefined in a way that is useful.
Jack, I don't feel I've really received an answer to my questions. I see things that may be intended to be statements of what you think is the case, having come after other statements that could have been intended as definitions of "macro" or "micro".
I'm trying to separate out which are statements that you believe or propose to be (possibly hypothetical) statements about "micro" or "macro" evolution from what you are proposing as the definition you would intend to use.
I'm fine with multiple candidate definitions too -- in that case you might number the candidates.
I would caution that statements that appear draw conclusions might be taken as very confusing attempts at a definition.
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Rex Kerr
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posted 04. September 2003 21:53
I am not aware of any sensible mapping between an organism's genotype/phenotype and the notion of "inventiveness" (or evolvability).
Therefore, until such a mapping has been made explicit, has been demonstrated to behave reasonably on test cases, and so on, I see no reason to seriously entertain the idea of shifting the definition of macroevolution (which is currently moderately well-defined) to depend on those terms (which would render it poorly-defined).
Now, if notions of inventiveness and evolvability could be made rigorous, it would be quite interesting, and then it might be worth thinking about shifting definitions of macroevolution to take them into account. (Alternatively, one might come up with different terms such as "endoevolution" and "exoevolution" if the traditional macro/micro division still seemed useful and if endo/exo distinctions were largely orthogonal to micro/macro distinctions.)
But as it is, we're putting the cart before the horse. Let's first examine what can be accomplished by classifying evolution on the basis of evolvability/inventiveness.
For example, Jack listed:
quote:
macro, invention, variation-driven, internal, low-probability, "quantum" leaps, complexity, enhanced evolvability, non-Darwinian
vs.
micro, tuning, selection-driven, external, hi-probability, gradualist, efficiency, fixed evolvability, Darwinian
But this raises a huge number of questions (as does any clustering of terms into two conflicting groups).
Is speciation inventive? Is inventiveness variation-driven? Is "internal" inventive? Is variation-driven "internal"? Is being driven by variation low-probability? Is inventiveness low-probability? And so on.
I think this list gives us an excellent set of questions to consider.
For example: should we consider Darwinian or cognitive/logical processes more inventive? If we look at the cases where we are sure which path was taken--for instance, program design by evolutionary algorithms vs. conventional human software design--the evolutionary algorithm seems more inventive to me. When I look at the Avida programs that compute EQU, they seem nonintuitive, weird, and yet they work; upon understanding them, they seem to "think outside the box" that normal human programmers think in. Human inventiveness is more obvious when it comes to high-level structure of a program. So my answer would be: Darwinian processes are locally much more inventive than "intelligent" processes, while "intelligent" processes are more inventive in an overview or outline-level.
Unfortunately, this doesn't lead me to categorize biological organisms in any particular way, because (for example) different species have many, many differences on a local level as well as the differences in the large-scale level. We're only beginning to classify all the small-scale differences (e.g. by sequencing genomes) so it would be presumptuous to decide at this point that the large-scale differences are all that matters.
This also raises the question: are there clearly separate classes of "micro/endo" vs. "macro/exo" evolution, under any definition? Or does the distinction simply not exist as a sharp line? My impression has been that there isn't a sharp line, unless you draw one artificially.
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Jack Foster
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posted 04. September 2003 23:13
Hi Rex:
quote:
I am not aware of any sensible mapping between an organism's genotype/phenotype and the notion of "inventiveness" (or evolvability).
An evolutionary system's evolvability is vitally dependent upon the primitives which map gene to phene. I believe that evolvability is a multi-variable quality, but I think it's been adequately shown that without a sufficient genotype/phenotype relationship, there IS no evolvability.
quote:
But this raises a huge number of questions (as does any clustering of terms into two conflicting groups).
Is speciation inventive? Is inventiveness variation-driven? Is "internal" inventive? Is variation-driven "internal"? Is being driven by variation low-probability? Is inventiveness low-probability? And so on.
I think this list gives us an excellent set of questions to consider.
Thank you. I mentioned earlier on the thread that the different list items would give different dividing lines. The main point is that evolution can indeed be classified into categories. Some people insist that evolution = evolution, but it seems to me that the notion is politically derived and not realistic.
quote:
For example: should we consider Darwinian or cognitive/logical processes more inventive? If we look at the cases where we are sure which path was taken--for instance, program design by evolutionary algorithms vs. conventional human software design--the evolutionary algorithm seems more inventive to me. When I look at the Avida programs that compute EQU, they seem nonintuitive, weird, and yet they work; upon understanding them, they seem to "think outside the box" that normal human programmers think in. Human inventiveness is more obvious when it comes to high-level structure of a program. So my answer would be: Darwinian processes are locally much more inventive than "intelligent" processes, while "intelligent" processes are more inventive in an overview or outline-level.
Remember that I'm calling inventiveness due to variability NON-Darwinian. I don't mean this in any derogatory way; I just mean that without the proper building blocks . . . the proper variation-side evolvability, selection is impotent. In the EQU example, there were 26 non-random primitive building blocks provided for evolution, and fitness checkpoints designated along the path to EQU. Without appropriate primitives, EQU would not evolve. (And without the checkpoints -- the smoothing of the fitness terrain -- EQU did not evolve.)
(Remember also that this is a modest accomplishment. For all of the congratulations and gusto shared, you would think cancer was cured! You consider this "more inventive" because it was chanced into. But this wasn't a problem that would be difficult at all for intelligent inventiveness. And it wouldn't have been solved by evolution without the appropriate non-Darwinian, variation-side evolvability.)
I'm mostly interested in that first checkpoint: function. Most functions must involve more than one variable. Sensory perception, for instance. It's not enough to chance into a light sensitive cell. There must also be some kind of communication from that cell. This invention cannot be selection-driven; evolution must have the right primitives at its disposal.
quote:
This also raises the question: are there clearly separate classes of "micro/endo" vs. "macro/exo" evolution, under any definition? Or does the distinction simply not exist as a sharp line? My impression has been that there isn't a sharp line, unless you draw one artificially.
I agree that there's not necessarily a sharp line, so maybe any differentiating concept between types of evolution will be arbitrary. Still, it's better to acknowledge differences where there are indeed differences.
[ 04. September 2003, 23:18: Message edited by: Jack Foster ]
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Rex Kerr
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posted 05. September 2003 00:23
We can make distinctions between tall people and short people, fat people and skinny people, people with long hair and people with short hair. However, as these examples show (especially the first two), just because there is difference doesn't mean that there's meaningful separation.
Height, for instance, follows close to a Gaussian distribution. It would be foolish for any comprehensive theory of humans to only consider the "tall person"/"short person" dichotomy, as most people are neither particularly tall nor particularly short, and any arbitrary dividing line near the middle will have many people close to it and thus will be considered very differently in the theory when in fact they're almost identical.
Thus, whenever someone proposes a distinction, I view it in this light: is this a well-defined and significant distinction? I'm unconvinced that there is a well-defined and significant distinction in evolution regarding inventiveness vs. the alternative.
For example, with your light-sensitive cell thought experiment: suppose we start with a cell that is already performing a signaling function, and we get a point mutation in the electron transport chain that renders a cytochrome especially sensitive to light, leading to mitochondrial damage and spurious activation of signaling pathways (followed by death if the exposure is too great). There we have a very slightly light sensitive cell, which could be selected for, via a process that could hardly be called anything but Darwinian.
This goes back to the old IC arguments; IC could be viewed as a claim about inventiveness. But that's the whole question: is apparent inventiveness (with large jumps) actually the result of lots of local optimization (& variability & so on)? If the answer was no, apparent IC implies large jumps of low-probability inventiveness are necessary, and if the difference between major evolutionary groups involved the existence of new IC systems, then it would be appropriate to separate macroevolution and microevolution along the lines of inventiveness. (There may be other reasons to perform the separation, but they aren't occuring to me right now.)
Also, you say that "an evolutionary system's evolvability is vitally dependent upon the primitives which map gene to phene". Sure. But is that all that counts as inventiveness? And what about that counts? Only the core translation machinery? How about splicing? Chaperones? If you duplicate your chromosomes, allowing many genes to drift (and increase variability), is that an increase in evolvability? How about if you duplicate a single gene? Add a single base pair?
You do need a genotype/phenotype mapping to get evolvability (i.e. you need to select based on the genotype, in some fashion), and certain regimes work better than others. However, when studying biology our job is not to set up these mappings from scratch; rather, we have them. Given what we have--or what we had--one wonders what we can get. One also wonders how they could have come to exist, but when you are still struggling to explain the evolvability of current systems, it's rather premature to draw any firm conclusions about the evolution of evolvability. (It may, nontheless, be fun to speculate on.)
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Jack Foster
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posted 05. September 2003 13:40
Excellent post, Rex.
quote:
Height, for instance, follows close to a Gaussian distribution. It would be foolish for any comprehensive theory of humans to only consider the "tall person"/"short person" dichotomy, as most people are neither particularly tall nor particularly short, and any arbitrary dividing line near the middle will have many people close to it and thus will be considered very differently in the theory when in fact they're almost identical.
All of the distinctions I'm making have polarity, I believe. Most of the evolution that we see -- moth wings and bird beaks -- involves the selection of pre-existing morph alleles. There's no new mutation in this. At the other pole, invention of new function --say replication for the first self-replicator -- cannot involve selection until after the fact.
Likewise, efficiency and complexity are poles. As loose example, beneficial deletions promote efficiency, whereas duplication and divergence promote complexity. So if we were to advance this distinction definitionally, duplication would be viewed as a macroevoloutionary mutation. (Again, this is a different distinction than the inventiveness/tuning distinction.)
quote:
Also, you say that "an evolutionary system's evolvability is vitally dependent upon the primitives which map gene to phene". Sure. But is that all that counts as inventiveness? And what about that counts? Only the core translation machinery? How about splicing? Chaperones? If you duplicate your chromosomes, allowing many genes to drift (and increase variability), is that an increase in evolvability? How about if you duplicate a single gene? Add a single base pair?
Evolvability and inventiveness are also different distinctions, but all of these have a broad overlap, I believe. Your questions are good ones.
I think evolutionary biology needs a new theory of variation. It should be embarrassing for people to claim that all of evolution can be explained by the dynamics of population genetics! When talkorigins or others claim that microevolution is the same thing as macroevolution, people should at least be aware of the distinctions.
What should the new theory look like? Hey, I'm just a layman. But it seems to me that there should be recognition that while mutations may be stochastic and not directed, they are not truly random either in that a uniform distribution in genotype space maps to a non-uniform distribution in phenotype space. I'm really interested in the nature of the primitives at all levels of evolution that lead to this result. I think a new theory can be completely naturalistic, but I would like to see some fine-tuning analysis from the ID camp. Certainly biological evolution is extraordinary; perhaps we can begin to elucidate why it is extraordinary.
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gedanken
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posted 05. September 2003 14:55
Before we move to "theory" we might want to be clear on our definitions.
I understand that Jack wants to give some new definitions to terms -- perfectly fair. (If we wanted the scientific community to use them, we might choose different words than they already use for another purpose, but that does not really affect the basic concept of defining a new term to see if we can use it productively to make distinctions in nature.)
But I am still confused as per some of my previous questions.
What I cannot tell is which statements are intended to be observations which we can analyze based on our definitions, and which are intended to be the definitions themselves.
We could fairly take "homology" (in its modern definition) as an example. Homology is (if I have it right) similarity due to descent. This appears to make a statement about scientific observational matters. (Similar to some of Jack's statements could be used as definitions even though they might appear to make a statement about observable matters.)
But that would oversimplify the case. In thusly defining homology, we don't presuppose that there exist any homologies just because we define the term in terms of a process.
Still some of Jack's statements have confused me, as they include statements of implication. Any proposed definition should be clear and without assumption that it will be found in nature, but rather simply state a condition or descriptive relationship. Then statements of implication that might come from observations, using that definition, should be given separately and should be clear to the reader as statements that are intended to describe the real world and are thus subject to observational verification.
To be carefully exact in my point, no definition of terms can simultaneously be a statement about nature. Definitions are not something that are true and false according to observation, the concept of definition is intended to be a statement of substitution of one word or phrase for a more complex set of descriptive phrases.
So I am recommending clarifying which is definition, and which is statement of relationships intended to be considered (possibly hypothetical) aspects of nature. In that way one can work toward having a set of relationships and observations that connect with the definitions given, and then by finding that these are well-supported by observation one works toward "theory".
[ 05. September 2003, 15:03: Message edited by: gedanken ]
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Jack Foster
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posted 05. September 2003 17:24
Hi gedanken:
For the time being, I'm happy to have pointed out distinctions. At the risk of frustrating you further, I'll forego the opportunity to formalize any definition at this point. Rex had a good point when he talked about distinctions needing to be well-defined and significant. I'll leave it to others better qualified than I to determine if any of the distinctions on my list are significant enough to merit formalization through the addition to lexicon.
regards and thanks for your input,
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Rex Kerr
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posted 05. September 2003 18:49
Height has polarity, as does binary logic (true/false) so I'm unsure what Jack is getting at in his first response to me. My point was that the distribution was important when deciding whether you want to talk about the two poles, or about the average, or about a continuum.
Jack also said:
quote:
it seems to me that there should be recognition that while mutations may be stochastic and not directed, they are not truly random either in that a uniform distribution in genotype space maps to a non-uniform distribution in phenotype space
but I don't know of any geneticist who doesn't recognize exactly that. So not only should there be such a recognition, there is! He continues:
quote:
I'm really interested in the nature of the primitives at all levels of evolution that lead to this result.
Among other things, the protein folding problem (i.e. given a certain amino acid sequence, what shape will the resulting protein form) is an extraordinarily nonlinear mapping between genotype and phenotype. The existence of that non-uniformity (and its basis (if not solution) in physical laws, e.g. electrostatics) are well-understood, so I'm not sure what primitives Jack is looking for.
Gedanken makes some very good points about definitions vs. implications. I second his comments.
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Jack Foster
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posted 05. September 2003 22:03
quote:
Height has polarity, as does binary logic (true/false) so I'm unsure what Jack is getting at in his first response to me. My point was that the distribution was important when deciding whether you want to talk about the two poles, or about the average, or about a continuum.
I don't disagree with your point, but I don't think my response was particulary ambiguous, either. You talk about "no meaningful seperation" and gave as an example the bell curve distribution of height. (Though now you think height has "polarity", so you must be using the term in a different way than I was.) I pointed out that almost all of the evolution that we see sits at one pole (selection-driven), and all of evolution's invention of function by logical necessity must sit at the other (variation-dependent). So what's confusing about this for you?
quote:
but I don't know of any geneticist who doesn't recognize exactly that (the non-random nature of phenotypical variation). So not only should there be such a recognition, there is!
I didn't claim that geneticists DIDN'T recognize this, though I think it's good news that you think they do!
quote:
Among other things, the protein folding problem (i.e. given a certain amino acid sequence, what shape will the resulting protein form) is an extraordinarily nonlinear mapping between genotype and phenotype. The existence of that non-uniformity (and its basis (if not solution) in physical laws, e.g. electrostatics) are well-understood, so I'm not sure what primitives Jack is looking for.
Again, I didn't say I was "looking for primitives". Like everyone else, I'm trying to gain whatever insights that I can about evolution. Aside from life, all evolutionary systems that we know of were designed by man. The interesting evolution happens in most part due to the design of variability: the primitives included in the gene to phene map. Sims' VIRTUAL CREATURES evolves life-like creatures precisely because of the primitives that Sims included. If someone were to examine the code of several of the creatures, they could make strides at reverse-engineering the evolutionary system. They could identify primitives.
Evolutionary biologists have done this very thing with biological evolution, but obviously they're a long way from understanding evolution. I'm simply asking what about the primitives allow for the vast open-ended evolution that we see in life? If Rex thinks this is "well-understood", then maybe he can explain it all to us. Start with consciousness, Rex.
I'm probably done with this thread. Thanks for your participation gedanken and Rex.
[ 06. September 2003, 23:37: Message edited by: Jack Foster ]
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