Friday, March 17, 2006
Semi-Meiosis and Prescribed Evolution
John Davison requested that I post an old paper of his on the web for people who are interested. The paper is Semi-Meiosis as an Evolutionary Mechanism from the Journal of Theoretical Biology in 1984. Also, I scanned in his response to comments on his paper (unfortunately, I do not have a copy of the comments themselves).
Davison's hypothesis has been refined over the years, and it has recently emerged as the Prescribed Evolutionary Hypothesis. The idea is that ontogeny (development from an embryo to a full-grown organism) and phylogeny (the diversification of organisms through time) are similar processes. Both follow a planned set of changes, which are self-limitted. In ontogeny, development stops in the adult form. In phylogeny, progress stops when the organisms have finished diversifying. He views obligatory sexual reproduction as the halting event for phylogeny. Semi-meiosis is a form of reproduction that Davison hypothesizes was the norm before obligate sexual reproduction, which enabled major gene reorganizations without having the problems of finding a suitable mate, or diluting the effect of the change.
Anyway, this is more-or-less the quintessential non-Creationist Intelligent Design hypothesis. It has evolution proceeding, but proceeding not by random processes, but according to an orderly, more-or-less predetermined process.
Interestingly, while Davison thinks absolutely that large-scale evolution has occurred in the past, he similarly thinks that it is _not_ happening today. He gives evidence for this in his paper Is Evolution Finished? The reason for the change is that, like ontogeny, phylogeny has a final form that it attains, after which it stops developing -- it self-limits.
Anyway, as a Creationist, I disagree with several of his points, but they are all worth consideration. Kurt Wise has put forward some similar ideas, though in a much more limitted form (see pgs 7-11 of that paper). Davison does not have much tolerance for Creationists such as me, as he puts it "A past evolution is undeniable. A present evolution is undemonstrable."
Also of interest is that I think Davison has come to disagree with monophyly. He does not view man as a separate creation as Creationists do, but I think I remember him mentioning that Primates may in fact be a separate starting point of phylogeny, as well as other taxonomic groups.
Dr. Davison -- if you are reading this and I have misrepresented your ideas in any way, please correct me in the comments below.
Davison's hypothesis has been refined over the years, and it has recently emerged as the Prescribed Evolutionary Hypothesis. The idea is that ontogeny (development from an embryo to a full-grown organism) and phylogeny (the diversification of organisms through time) are similar processes. Both follow a planned set of changes, which are self-limitted. In ontogeny, development stops in the adult form. In phylogeny, progress stops when the organisms have finished diversifying. He views obligatory sexual reproduction as the halting event for phylogeny. Semi-meiosis is a form of reproduction that Davison hypothesizes was the norm before obligate sexual reproduction, which enabled major gene reorganizations without having the problems of finding a suitable mate, or diluting the effect of the change.
Anyway, this is more-or-less the quintessential non-Creationist Intelligent Design hypothesis. It has evolution proceeding, but proceeding not by random processes, but according to an orderly, more-or-less predetermined process.
Interestingly, while Davison thinks absolutely that large-scale evolution has occurred in the past, he similarly thinks that it is _not_ happening today. He gives evidence for this in his paper Is Evolution Finished? The reason for the change is that, like ontogeny, phylogeny has a final form that it attains, after which it stops developing -- it self-limits.
Anyway, as a Creationist, I disagree with several of his points, but they are all worth consideration. Kurt Wise has put forward some similar ideas, though in a much more limitted form (see pgs 7-11 of that paper). Davison does not have much tolerance for Creationists such as me, as he puts it "A past evolution is undeniable. A present evolution is undemonstrable."
Also of interest is that I think Davison has come to disagree with monophyly. He does not view man as a separate creation as Creationists do, but I think I remember him mentioning that Primates may in fact be a separate starting point of phylogeny, as well as other taxonomic groups.
Dr. Davison -- if you are reading this and I have misrepresented your ideas in any way, please correct me in the comments below.
Permanent Link posted by crevo @ 9:12 PM 
Comments:
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Crevo
Thank you very much for presenting these two papers for consideration. I agree with most of what you have said about my views.
There are just a couple of points I would like to make. I have no idea how many times life was created. It may have been once or ten thousand times. There is now convincing chromosomal evidence that all primates share a common original ancestor or ancestors. How much further this can be extended is not yet clear.
The independent evolution of sex-determining mechanisms and the separate modes of origin of the sex cells indicate separate origins but by no means prove it for the various vertebrate classes and for the amphibian orders Anura and Urodela. Similar arguments apply for the various classes of arthropods who also have non-homologous sex cells and modes of sex determination at least in some instances.
Also I have never rejected a personal God. What I have indicated is that I see no evidence for one. My God or Gods, like Einstein's, lack personality as nearly as I can determine. That does not mean I am correct. As I put it in my Manifesto:
"God works in mysterious (semi-meiotic) ways."
Since then I would replace works with worked. As you indicated, I believe creative evolution is quite finished with man the terminal mammalian product. The terminating mechanism for progressive evolution has always been the same fundamental reproductive mode which is obligatory sexual reproduction. This has been independently invented several times during evolutionary history. I do not believe this mode is capable of progressive evolution even to the extent of providing a new species in the same genus. Until that is demonstrated experimentally, I will remain of that persuasion. I also see no evidence that any contemporary life forms are capable of ever becoming anything very different from what we see right now.
My primary thrust has always been to give proper credit to my many predecessors who provided me with the necessary material to formalize the Prescribed Evolutionary Hypothesis.
"A dwarf standing on the shoulders of a giant may see farther than a giant himself."
Robert Burton
Let there be no quesion, I am happy to be that dwarf. Thank you again.
Thank you very much for presenting these two papers for consideration. I agree with most of what you have said about my views.
There are just a couple of points I would like to make. I have no idea how many times life was created. It may have been once or ten thousand times. There is now convincing chromosomal evidence that all primates share a common original ancestor or ancestors. How much further this can be extended is not yet clear.
The independent evolution of sex-determining mechanisms and the separate modes of origin of the sex cells indicate separate origins but by no means prove it for the various vertebrate classes and for the amphibian orders Anura and Urodela. Similar arguments apply for the various classes of arthropods who also have non-homologous sex cells and modes of sex determination at least in some instances.
Also I have never rejected a personal God. What I have indicated is that I see no evidence for one. My God or Gods, like Einstein's, lack personality as nearly as I can determine. That does not mean I am correct. As I put it in my Manifesto:
"God works in mysterious (semi-meiotic) ways."
Since then I would replace works with worked. As you indicated, I believe creative evolution is quite finished with man the terminal mammalian product. The terminating mechanism for progressive evolution has always been the same fundamental reproductive mode which is obligatory sexual reproduction. This has been independently invented several times during evolutionary history. I do not believe this mode is capable of progressive evolution even to the extent of providing a new species in the same genus. Until that is demonstrated experimentally, I will remain of that persuasion. I also see no evidence that any contemporary life forms are capable of ever becoming anything very different from what we see right now.
My primary thrust has always been to give proper credit to my many predecessors who provided me with the necessary material to formalize the Prescribed Evolutionary Hypothesis.
"A dwarf standing on the shoulders of a giant may see farther than a giant himself."
Robert Burton
Let there be no quesion, I am happy to be that dwarf. Thank you again.
Incidentally, you do not recognize any comment at the end of the introduction to the thread. Maybe your system does not automatically tally comments as mine does.
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