Boredom and recombination1
jrg13 at PSU.EDU
Tue Feb 5 23:15:24 CST 2002
At 10:33 AM 2/5/02 +0100, you wrote:
>Your response reached me off-list - if you did not intend it that way you
>may repost it with this reply.
Thanks, my comments are inserted into the next email. JOhn
>At 09:52 AM 2/4/02 -0500, you wrote:
>>I know some people on the list are not so bored with Croizat so perhaps
>>Hovenkamp's warning is no more necessary than it would be for Darwin,
>>Mayr, Gould, Van Steenis etc.
>>I appreciate Hovenkamp's concern over hybridization, but I was not
>>restricting my remarks about character recombination to hybridization and
>>I did not view reticulate evolution as synonymous with hybridization.
>>Croizat used the term character combination to refer to a process of
>>reticulate evolution - I did not say that Croizat used the latter term.
>The subject came up in a context where I understood "reticulation" to
>refer to hybridization and introgression - only after I closed and went
>home I realized that this might not really be your understanding.
>Nevertheless - your correction actually reinforces my point: from reading
>your original post, people might get the impression that Croizat was
>saying something interesting about the role of hybridization. He was not.
>The "reticulate evolution" you talk about seems to me to be much better
>described by Croizat's "character recombination": it refers to the
>observed patterns, not to the inferred processes ("evolution"). I was
>taught as a student to make a distinction between reticulate patterns and
>reticulate evolution - I still think it is a useful distinction.
>>>p. 520: "(...) hybridization took place here and there during spells of
>>>mobilism followed in immobilism (C.means during subsequent spells of
>>>immobilism, note PH) by re-combination of characters of permanent nature,
>>>whatever the technical process in detail."
>>>To me, it is clear that hybridization and character recombination are to
>>>Croizat two completely different processes, which need not coincide in time.
>>It seems to me by the p. 250 quote that hybridization may represent one
>>of the 'technical processes in detail', but on the other hand a full
>>analysis of the subject may show Hovenkamp to be correct.
>Don't wait up for me trying to prove myself correct by a full analysis of
>Croizat's writings ;-).
>>>This is of course rather surprising, as hybridization offers such a good
>>>expanation of observed character recombination. Yet Croizat seems not to
>>>have thought of that. But then, what he called character recombination is
>>>not what we casually call character recombination.
>>The Royal "We" aside, I think Croizat was focused on a broader process of
>>character recombination than just the individual process of hybridization
>>in the technical sense of different lineages coming together. However in
>>Croizat's concept of a differentiated ancestor there is the likelihood of
>>partially differentiated entities interacting genetically. Heads has
>>referred to this as ancestral hybrid swarms.
>I suppose "differentiated ancestor" is a typo for "undifferentiated ancestor"?
>For the rest of this statement, it seems to me rather unspectacular to
>allow for the fact that ancestors may consist of a number of somewhat
>differentiated but not fully isolated populations. But the connection of
>this to a better understanding of Croizat's concept of character
>recombination eludes me.
>>>His concept of character recombination refers to parallel evolution of
>>>similar combinations of character states.
>>Perhaps, but this was not my impression. Perhaps a subject for future study.
>>>be added: "in evolution old characters are being combined and recombined
>>>without cease rather than new characters constantly called into being" (p.
>>It was not my impression that new characters were excluded. However, the
>>importance of recombination in differentiation was certainly emphasized.
>>So while the evolution of the feather may involve the recombination of
>>five 'fish' scales, it does not necessarily mean that every aspect of the
>>feather morphology was already present (preformed) in the fish scale.
>Impressions may vary, even after reading the same text. Much of postmodern
>philosophy comes down to that point, I believe. But somehow the problem
>seems greater for texts by Croizat than by most other authors in the last
>2 centuries (restricting myself to authors on scientific subjects).
>>>Thus, it is not necessary to invoke hybridization or reticulation -
>>>it was enough to recognize that "form making" could simply flip any number
>>>of switches at any time.
>>I don't know about 'any number'
>My impression was that Croizat did not restrict character recombination to
>any specified number of characters.
>>>I will not go into John Grehans first statement - that "traditional
>>>evolutionary models" have neglected reticulate evolution. It just shows
>>>that he's not a botanist.
>>It seemed to me that they have in the sense of Croizat's character
>>agree that reticulate evolution through hybridization is not neglected.
>>However, with respect to Hovenkamp's point I was making a statement about
>>general evolutonary models. It is probably that there are individual
>>models that do correspond with Croizat's concept.
>In which case I do not understand your remark at all...
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