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Author
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Topic: Common descent
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Evan
Member
Member # 164
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posted 02. April 2002 10:38
I am taking Paul’s advice and starting a new thread focussed on common descent, although I think this topic will necessarily need to also include parts of the discussion of “miraculous” that was present in our previous discussion.
In a previous thread, I had written,
quote:
Also, I do not claim that " the rule omne vivum ex vivo ...holds irrespective of whatever discontinuities we observe." If we were to in fact observe discontinuities in the chain of biological relationships, then of course we would take that into consideration. But we don't observe such discontinuities.
Paul responded,
quote:
Really? You're more sanguine that most evolutionary biologists I know, who struggle valiantly to explain how evolution bridged the manifold discontinuities in form and function among organisms.
I think Paul is referring to a different type of discontinuity than I am.
I am aware that many argue that the theory of evolution fails to account for the fundamental differences that seem to exist at various levels between one species and the next - that there are periods of species stability and then what appears to be sudden appearances of the next species (and the same is true of various structures and functions.)
These are not the type of discontinuities that I am referring to.
I am referring to two other types of discontinuities:
1) The first is true breaks in the flow of cause-and-effect: times where, as Dembski says, something other than what would have been produced by law-and-chance happens instead. These he defines as “miracles.” A gross example would be, as I said before, someone walking down the street suddenly (instantaneously) moving 100 feet in a step, or a new creature suddenly (again instantaneously) materializing into existence. A more subtle example would be a moving particle suddenly changing direction even though no force was applied to it.
2) The other sense in which I am using discontinuity is in the sense of breaks in the chain of parent-child relationships. We definitely do not see new organisms coming into existence in any other way.
These are the two types of discontinuities that I claim have not been observed. Paul misunderstood this, and thought I was referring to a more general type of biological discontinuity.
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The critical point is that I have put a forth an ID hypothesis by which the type of biological discontinuities that Paul is concerned with can be explained without invoking either of the types of discontinuities that I am referring to: the improbable and relatively sudden emergence of biological novelty can take place without “miraculous” discontinuities in the flow of natural law and without any break in the chain of common descent.
Because of this, I do not see why one would need to deny common descent. The intelligent designer, as my hypothesis offers, could create biological novelty by making successive small changes in the genomes, and hence the offspring, of a number of creatures over a number of generations; and furthermore, could do so “non-miraculously” by manipulating probabilities at the quantum level.
No break in the chain of common descent is necessary, so unless other arguments can be presented as to why common descent should be doubted, parsimony (among other things) leads me to accept common descent.
[ 02 April 2002, 10:40: Message edited by: Evan ]
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Paul A. Nelson
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posted 02. April 2002 12:00
Hello Evan,
May I suggest that we sharpen our focus a bit more? I propose that we discuss the following paper, by Malcolm Gordon of UCLA, which argues for polyphyly at a level (post-Cambrian Explosion) you find significant (and also where you do not see evidence for discontinuity):
Malcolm S. Gordon, "The Concept of Monophyly: A Speculative Essay," Biology and Philosophy 14 (1999): 331-348.
[from the abstract]: The concept of monophyly is central to much of modern biology. Despite many efforts over many years, important questions remain unanswered that relate both to the concept itself and its various applications. This essay focuses primarily on four of these: i) Is it possible to define monophyly operationally, specifically with respect to both the structures of genomes and at the levels of the highest phylogenetic categories (kingdoms, phyla, classes)? ii) May the mosaic and chimeric structures of genomes be sufficiently important factors in phylogeny that situations exist in which the concept may not be applicable? iii) In the history of life on earth were there important groups of organisms that probably had polyphyletic, rather than monophyletic, origins? iv) Does the near universal search for monophyletic origins of clades lead, on occasion, to both undesirable narrowing of acceptable options for development of evolutionary scenarios and sometimes actual omission from consideration of less conventional types of both data and modes of thought, possibly at the expense of biological understanding?
Please let me know if you have access to this paper, and if you think it is worth discussing. Rather than bouncing abstractions back and forth, I'd like to move to nuts and bolts.
[ 02 April 2002, 12:02: Message edited by: Paul A. Nelson ]
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Moderator
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posted 02. April 2002 12:16
Thanks Paul for bringing up a specific paper.
Evan, you have started several threads recently that border on "off-topic" for Brainstorms. Why is that? Because they bring up the typical, old, worn debates that persist to this day in other forums around the web. Brainstorms is trying to carve out a niche where positive arguments/inutitions are made in reference to complex systems.
This is NOT an Intelligent Design or evolution forum. It is a forum for discussion about complex systems (from the perspective of biology, engineering, physics, information science, etc.).
So, I'm going to let this discussion persist, because I see that we are getting to specifics regarding the origin of complex systems (the paper that Paul cites). However, my finger is on the trigger just in case the thread diverges.
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Evan
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Member # 164
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posted 02. April 2002 23:09
I have written the moderator privately about his message to me. I hope his response clarifies what aspects of my posts and general participation here at ISCID are inappropriate and off-topic, and which aren’t.
I also would like to respond to Paul:
Paul writes, “Please let me know if you have access to this paper, and if you think it is worth discussing. Rather than bouncing abstractions back and forth, I'd like to move to nuts and bolts.”
No, I do not have access to the paper you mention. I am not a biologist, and am not qualified, I imagine, to discuss all the paper’s details. I am qualified to discuss, I think, more general issues, and that is what I am interested in.
I realize that you consider such issues “abstractions” as opposed to “nuts and bolts,” and I certainly appreciate the need for details at times. I also think that sometimes one needs to consider the forest and not the individual trees. So it looks like you and I are perhaps not interested in discussing things at the same level. Thanks for the offer, anyway -perhaps some other ISCID member will be interested in taking up the conversation from here.
However, I do believe there should be a place in the framework of ISCID’s purpose for general, non-technical consideration of the ideas brought up by Dr. Dembski in particular, and by others working on understanding complex systems. I hope this is the case, because I would like to continue to participate here, and I think I can make a positive contribution to at least some of the conversations.
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Moderator
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posted 03. April 2002 00:48
Dear Evan,
I did not receive the private email that you sent to me.
However, I certainly want to clarify because your overall contribution to our forum has been positive, and I may not have given that impression in my previous warning.
quote:
I do believe there should be a place in the framework of ISCID’s purpose for general, non-technical consideration of the ideas brought up by Dr. Dembski in particular, and by others working on understanding complex systems.
There is a nuanced distinction to be made here, and I hope that I can articulate it clearly enough. Essentially, ISCID does not want to duplicate the work of other organizations. Particularly, Brainstorms is not intended to be a place to discuss typical/general issues relating to Intelligent Design and evolution. Questions that have been hashed out time and time again are off limits here. Novel hypotheses and intuitions are welcome. I've sensed a delicate balance between the two in your[Evan] posts. Try to steer more towards the novel hypotheses and away from the stuff like age of the earth, common descent, etc. which have been prevalent in your recent posts.
If you'd like to discuss this further, please email moderator@iscid.org.
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New York Wiseguy
Member
Member # 210
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posted 03. April 2002 07:37
This topic being a carryover from "Summarizing the Issues", I would like to start with some "unfinished business" from that Topic.
To Paul Nelson:
I am appreciative of the time you took to describe your course of study at UC. Sounds like a magnificent educational experience.
'a carefully focused discussion on the theory of natural selection, or the theory of common descent, or the definition of "miracle" (in relation to intelligent causation), or how we infer the past -- but not on all of these topics at the same time'
I'm going to be interested in seeing how common descent can be discussed in total isolation from at least the two topics mentioned next in sequence.
To Mike Gene:
'Nor is it a place where we can call people like Paul Nelson or Bill Dembski to the computer in order to have them explain themselves.'
I have not expected that it was. In the case of Dr. Dembski, I had hoped that someone more familiar than I with his writings could identify for me where he spells out the manner in which he would seek to redefine science. Paul seems willing to engage, which I appreciate.
'lack of "closure"'
I have not had nearly as much experience as you in participating in this type of forum, but enough to fully comprehend and agree with your characterization as to their nature. An article could be written on possible ground rules to achieve some progress in this regard. E. g., one possible type of "closure" could be for the two parties who are in disagreement to agree mutually on a short, two-sentence statement that accurately summarizes their opposing views. I had thought that Evan and Paul stopped very short of that, and it could have been approached more closely.
To Evan:
'Ultimately, I am interested in what can be considered science.'
It continues to sound as if our interests are similar. Much of what I see on this forum seems to me to be discussion that starts out to be scientific and then quickly dissolves into philosophy.
To The Moderator:
'This is NOT an Intelligent Design or evolution forum. It is a forum for discussion about complex systems'
OK, that is something I had not really appreciated. I know the first sentence in the intro says it is about "complex systems". The name of the organization includes "Complexity, Information and Design", and I had been taking the intro wording as shorthand for all three subjects. My own personal outlook happens to be that the first two are scientific in content and the third is philosophic. It still seems to me problematical whether complex systems can be discussed at very great length without having the discussion dissolve into philosophy.
'...please make positive contributions regarding complex systems. Otherwise, simply lurk and learn.'
I do not know whether I will prove to be equipped to make what you will rate as positive contributions. I don't know whether you'd consider it positive if I were to be a whistle-blower calling attention to digressions into philosophy in what is supposed to be scientific discussion.
We'll see what happens. I might well have to retreat to lurking at a later time. But I'll give it a try.
And now on to this new, current topic:
I initially composed what is below before seeing Evan's response and the start of his colloquy with The Moderator. As in the case of Evan, I do not have ready access to the Gordon paper. But would we need it, or are we likely to be able to respond to quotes from it supplied by Paul? I wouldn't mind investing in a copy of it if I can be directed to a library that would supply a copy at a reasonable price. What follows is my intial reaction to the question of Nonophyly vs. Polyphyly. My initial reaction is that the paper could serve as a framework for further discussion of common descent. But I don't know if the Moderator will consider a debate on how best to make an informed judgment as to the validity common descent to be a topic of sufficient novelty for this forum.
The definition I see of "monophyletic" says "derived from a common ancestral type". Is that sufficiently precise? I'd assume, if we are talking post-Cambrian, and we are asking the question whether there is common descent for all vertebrates, would we be asking whether the newly-discovered Haikouella is likely to be the common ancestor of all vertebrates, as opposed to some vertebrates being from Haikouella and others from the earlier-known Pikaia? I believe there is concensus that Pikaia could not be a descendant of Haikouella.
Would I be correct in assuming that Monophyly would not require that there have been a single individual Haikouella to have been the common ancestor? I. e., there could be a question as to whether the invertebrate to vertebrate transition occurred by a population of previous invertebrates adapting themselves into vertebrates over many generations, as opposed to one pair only (assuming they reproduced bisexually) occurring somehow and becoming the common ancestors. If it was a population that evolved, i. e., a common "type" per the definition, does that still qualify as Monophyly?
The above questions have been aimed at making the discussion more concrete, but am I being too simplistic?
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Paul A. Nelson
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posted 03. April 2002 09:39
To Evan:
The moderator has said how he'd like you to try to frame your future contributions, and I'm going to help with that by not pressing further on the Malcolm Gordon article (given that you're not interested in discussing it in any case). But thanks for your questions and comments; I've enjoyed responding, although I think we could make more headway, much more quickly, if we were working together in a seminar room with a blackboard.
To New York Wiseguy:
I'll look for a good link (URL) or website giving clear definitions of basic systematic terms, such as "monophyly" and "polyphyly" (if anyone reading this knows of such a link or site, please provide it). The terminology of systematics is horrendous in its complexity. Briefly, however, "a monophyletic group is a group of species that includes an ancestral species and all its descendants, that is, a natural group. In other words, a monophyletic taxon is a group of species whose members are related to one another through a unique history of descent (with modification) -- a single evolutionary line" (R.C. Brusca and G.J. Brusca, Invertebrates [Sunderland, MA: Sinauer, 1990], p. 24). A polyphyletic group, by contrast, comprises species "that arose from two or more different immediate ancestors" (p. 25).
In the article cited above, Malcolm Gordon argues that terrestrial life itself -- the largest group known to biology -- and the tetrapods (a subdivision within the Phylum Chordata) are polyphyletic. Represented graphically, this would appear as multiple independent trees arising separately over time, at the point of the origin of life (for terrestrial organisms) and at the more recent point of the origin of tetrapods. To answer your particular question, if more than one chordate species gave rise to the rest of the chordates, and hence to the vertebrates, the Chordata would be polyphyletic, and cladists would therefore reject the group, insofar as their methodology is a search for strictly monophyletic groups.
Any good university science library should have the journal Biology & Philosophy. It shouldn't cost more than a dollar or so to copy the article. You may also be able to purchase the article on-line, from Kluwer Academic Publishers (which would be more convenient, albeit more expensive).
I'd encourage everyone to follow the moderator's lead, in his attempt to shape Brainstorms into a forum that does not duplicate fora elsewhere on the web (a good place for many of the questions raised here is the Intelligent Design forum at www.arn.org). Let me say that my interest in monophyly versus polyphyly connects to complex systems via probability questions, in particular, the mechanisms or processes by which biological novelty (e.g., the origin of the phyla) arises. If you do get and carefully read the Gordon article, NY Wiseguy -- a precondition for my further participation in this thread -- that is the specific direction in which I hope to take the discussion. Until then, I'll maintain radio silence.
[ 03 April 2002, 09:41: Message edited by: Paul A. Nelson ]
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New York Wiseguy
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Member # 210
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posted 03. April 2002 15:39
PN: ___I'll look for a good link (URL) or website giving clear definitions of basic systematic terms, such as "monophyly" and "polyphyly"___
NYW: Not necessary. Those two words were new to me, but I get the idea. The etymology of the words is interesting, if you were not aware. Neither of those two words appear in that form in the dictionaries in my library, but "monophyletic" and "polyphyletic" do. Webster's Unabridged gives generic definitions, but in the New International (1971) there is a snapshot of an earlier meaning in a much narrower context -- relating to the embryonic development of blood cells.
I have downloaded and read the Gordon article, and thanks for the referral to Kluwer, a quite useful resource. As you said, it was more expensive that way, but worth avoiding seeking out and traveling to a library. I'm not a Starving Student.
PN: ___If you do get and carefully read the Gordon article, NY Wiseguy -- a precondition for my further participation in this thread___
NYW: Done. Don't know if "carefully" enough to meet your requirement, but I certainly get what he's driving at.
PN: ___...my interest in monophyly versus polyphyly connects to complex systems via probability questions, in particular, the mechanisms or processes by which biological novelty (e.g., the origin of the phyla) arises.___
MYW: OK, you can now get into more specifics along those lines. I will describe how I'm taking it so far. If I had to make an even-money wager whether Gordon's thesis, 100 years from now, will be looked back upon as valid or invalid, I'd bet on invalid. (I admit my qualifications to render a judgment are quite meager). But--- His line of reasoning is sufficiently plausible that I wouldn't give heavy odds for the same wager, leaving me quite willing to carry on further discussion on the assumption that he is correct. Tell me if this is a valid metaphor in your eyes: "According to Gordon, the Tree of Life does not look so much like an Oak as it does like a Mangrove." OK, let's take that as a given, and now you can explain how that relates to "the mechanisms or processes by which biological novelty (e.g., the origin of the phyla) arises". I'll be most interested to hear what you build on Gordon in that direction.
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Paul A. Nelson
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posted 04. April 2002 09:08
Hello NYWG,
Thanks for getting and reading the Gordon article (on-line availability of journal articles is a wonderful innovation, although I'll take almost much any excuse to visit a library ;-)). I'll post my first set of comments in the next couple of days. In the interim, if you'd like to pop for another article, with relevance to this topic, see
Michael Syvanen, "On the Occurrence of Horizontal Gene Transfer Among an Arbitrarily Chosen Group of 26 Genes," Journal of Molecular Evolution 54 (2002): 258-266. Here's how Syvanen concludes the article -- this is the last paragraph:
A main suggestion of this paper is that the presence of the same biochemistry in two different lineages does not mean that their last common ancestor necessarily showed this trait. In fact, considerable energy has been expended in examining the biological unities found in all life as a means of gaining insight into the last universal cellular ancestor (LUCA) [long reference list snipped] ... The implications from the present work is that many of these determinations will reveal little about early ancestors. There has been recent discussion that horizontal gene transfer is so frequent that it may never be possible to reconstruct the last common ancestor (Kandler 1994; Doolittle 1999, 2000). However, if biochemical unities could be achieved after speciation events by horizontal gene transfer, then there is no reason to even postulate that a LUCA ever existed. If horizontal gene transfer is as common as I am implying, the modern cell could have evolved in multiple parallel lineages. Earliest life could have been truly polyphyletic." (p. 265)
And that's how the article ends.
I first heard Mike Syvanen lecture in September 1988, at the inaugural Molecular Evolution workshop held at the Marine Biological Laboratory (Woods Hole, MA). He argued, using data mainly from plants (as I recall), that molecular analyses could not resolve phylogenetic questions. He put up one slide after another showing conflicting molecular phylogenies, causing the audience to grumble and shift around uncomfortably in their seats. After Syvanen left the conference, Mitchell Sogin, the workshop director, publicly condemned the talk (which I thought was a cheap shot -- he should have said something while Syvanen was still there to defend himself). Anyway, Syvanen has for years argued that horizontal or lateral gene transfer (LGT) has been a major process in life's history, and now he seems to be receiving his vindication, in terms of many other workers picking up the banner of LGT.
I have lots of questions about LGT, however, and wish ISCID could somehow lure Mike Syvanen here to join the discussion. Mike, any chance you're reading this? If so, jump in when you think the water is warm enough.
Malcolm Gordon commentary to follow shortly.
[ 04 April 2002, 09:10: Message edited by: Paul A. Nelson ]
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New York Wiseguy
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posted 04. April 2002 11:23
Hello Paul Nelson:
I'll stick in a quick response while awaiting your further expansion from the Gordon article.
PN: ___although I'll take almost much any excuse to visit a library ;-)___
NYW: Likewise. Just a matter of expediency here, and eagerness to get on with it.
PN:___if you'd like to pop for another article__
Oh, oh, How far is this going to go? While I'm not a Starving Student, neither am I a spendthrift. As regards the Syvanen article, I believe I fully comprehend his premise, and I'm not sure I need to go through all his examples and technicalities to accept his premise as a valid departure point for further discussion. I'll add, further, that I am finding this very educational. It might well be that advocates of polyphyly such as Gordon and of the significance of horizontal gene transfer like Syvanen are gaining ground in the mainstream of evolution science. I might want to evaluate that further by searching for counterarguments from those who disgree with them (who I'm sure must be out there), but, as I've said, I'm very interested in seeing where the adoption of their ideas as starting points leads. I know that Steven J. Gould advocates the necessity of major revisions to neo-Darwinist theory. The end goal of my interest could be described as whether the work of Gordon and Syvanen leads more plausibly to a (1) a revision of neo-Darwinism or (2) support for the design inference.
PN:___the workshop director, publicly condemned the talk (which I thought was a cheap shot___
NYW: I'd agree. I have no sympathy for such close-mindedness against what might appear to be a maverick position.
PN: ___ISCID could somehow lure Mike Syvanen___
NYW: Why not contact him and extend a direct invitation?
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Alex Wild
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Member # 165
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posted 04. April 2002 20:48
Hi Paul. I have just finished reading Gordon’s paper, on your suggestion. I enjoyed his open perspective on the issue of tetrapod monophyly. However, my reading of Gordon is different than yours.
You wrote:
quote:
Represented graphically, this would appear as multiple independent trees arising separately over time, at the point of the origin of life (for terrestrial organisms) and at the more recent point of the origin of tetrapods.
Gordon did not mean multiple independent trees, but a web-like mesh of inter-relationships with possibly more than one root. Under Gordon’s scenario, the organismal trees are anything but independent. They are bound together by numerous associations and dissociations of different gene lineages. He isn’t arguing that each branch of life is separate from others, he argues that the individual gene trees that underly the broader organismal tree are so complex that the concept of the organism-level monophyly is not likely to be true. This is a gene-centered approach, in a way that I would say is Dawkins-esque.
Regarding the tetrapods, Gordon appears to be arguing about the monophyly of fossil tetrapods. In particular, he is saying that during the Devonian period when these things were alive, there may have been convergent evolution of more than one vertebrate lineage into a tetrapod form. He does not directly deal with extant tetrapods, and I suspect given the nature of his argument that he would find the extant tetrapods to be monophyletic with respect to the rest of the extant vertebrates.
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Paul A. Nelson
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posted 05. April 2002 09:10
Alex wrote:
Gordon did not mean multiple independent trees, but a web-like mesh of inter-relationships with possibly more than one root.
Think of a thick hedgerow. The branches of the individual bushes in the hedgerow have become (or grown up) so intermingled that it is nearly impossible, on a casual inspection, to separate them. This would be your "web-like mesh of inter-relationships." But if one kneels down and carefully locates the roots of the bushes, they are multiple and independent. One observes n + 1 roots (where n takes any value higher than zero).
Gordon writes, of the first origins of life:
"...this scenario [i.e., the one Gordon favors] should have resulted in many kinds of organisms having a variety of basic biochemistries and a variety of genetic compositions. The multiple kinds of proto-organisms produced in these ways presumably then reproduced, distributed themselves over the remainder of the earth's surface over varying periods of time, and evolved into the diversity of organisms that followed. Substantial amounts of horizontal transfer of genetic materials occurred by many different mechanisms, at many times and places, in many different directions, between many different groups, as did the development of various symbioses and the occurrence of widespread hybridization. Under this scenario life had multiple, polyphyletic origins, all of which have been inextricably intertwined....Life, therefore, is probably polyphyletic in origin." (pp. 336-337, emphasis added).
On Gordon's view, does the hedgerow of terrestrial life stem from a single root? No. If you look carefully at the bases of the bushes, you'll find multiple independent roots.
Hey Alex -- you're at UC Davis. If you ever run into Mike Syvanen, encourage him to visit Brainstorms.
Given that the rules here say that posts should be mostly original material, I'll add something about my upcoming longer comments on Gordon. Evolutionary phylogenetic reconstruction rests on what might be called a "biological singularity-seeking" methodology, where similarity above a certain threshold can be explained only by material descent (i.e., template causation, where there is a spatiotemporal relation of immediate physical action between parent object and offspring object: e.g., all the DNA strands in my body have physical ancestors in the gonads of either Gena Nelson or David Nelson, my parents). "Propinquity of descent is the only known cause of the similarity of organic beings" said Darwin in the Origin, and this principle has governed the reconstruction of the history of life ever since.
The problem is, this singularity-seeking methodology sits very uncomfortably with the research program of abiogenesis. There, the goal is to render the natural origin of life an event more likely than not to occur, given the right starting conditions. These two research programs, I suggest, are on a collision course with each other.
More later.
P.S. There is an exceedingly strange footnote on the origin of life in Gould's new book. See page 101 of The Structure of Evolutionary Theory. I've read the note about a dozen times, and I still can't quite believe it.
[ 05 April 2002, 12:12: Message edited by: Paul A. Nelson ]
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New York Wiseguy
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posted 05. April 2002 22:39
Paul:
Could you please quote that footnote from Gould? I was tempted by the book, but decided not to invest the time in reading it.
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edmund
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posted 07. April 2002 01:58
quote:
On Gordon's view, does the hedgerow of terrestrial life stem from a single root? No. If you look carefully at the bases of the bushes, you'll find multiple independent roots.
At least with respect to the tetrapods, Gordon is not-- according to my reading-- arguing that there are truly independent lineages involved. He is suggesting that multiple lineages of ancient fish, connected by common descent, converged on the terrestrial tetrapod lifestyle. All of these tetrapods shared a common ancestor; it's just that the common ancestor was a fish.
(To stretch the shrubbery metaphor: the different roots do meet, they just meet a few inches underground.)
As for the hypothesis that life came into being simultaneously at multiple points, and that these different proto-organisms merged to found the tree of life as we know it, I found his argument interesting but questionable. It seems to be founded mainly on the premise that the proto-organisms couldn't have gotten around very much. (He employs the same argument with respect to the late Devonian tetrapods.) I study a miserably sedentary insect which spends most of its life glued in place. It is a fantastically widespread invasive species. Based on this observation, my opinion is that a single type of proto-organism is quite likely to have spread over the globe during the geological time periods which presumably occurred between abiogeneses.
I think Gordon overstated the importance of polyphyly (though I applaud him for bringing it up at all). By sheer chance, I happen to know that one of the 'anomalies' he hopes to clear up by bringing polyphyly into the picture is in fact an egregious error committed in applying molecular clocks to estimate Cambrian divergence times! This made me wonder how well-founded his other arguments are.
Paul, if I understand you correctly, you feel that the search for monophyly conflicts with the attempt to account for abiogenesis because the latter wants abiogenesis happening behind every rock but the former is premised on it only happening once? I can see why there might be a conflict, but it certainly isn't inevitable. "Singularity-seeking" is the heuristic used in phylogenetic reconstruction, but phylogeneticists don't insist that reticulate evolution doesn't happen. It just muddies the water. Monophyly is definitely handy if you want to reconstruct common ancestors, but I don't think anybody claims that monophyly is the way things always happen.
--edmund
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Paul A. Nelson
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posted 07. April 2002 08:42
NYWG wrote:
Could you please quote that footnote from Gould?
In fairness to Gould, I probably shouldn't. If I were in his place, I'd want my readers to see the note in its complete context. I hesitated before adding the P.S. above, but I had just read the passage in question in Structure of Evolutionary Theory, and, in my reply to Alex, mentioning Gould's very curious note seemed apropos.
Here's the kernel of Gould's argument, anyway (which he actually made in Natural History magazine several years ago). There is something qualitatively different about the origin of life as an explanatory puzzle that places it outside not only the sphere of evolutionary biology, but perhaps even scientific explanation.
[ 07 April 2002, 08:50: Message edited by: Paul A. Nelson ]
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