Boredom and recombination

[P.Hovenkamp]

At 11:25 PM 2/5/02 -0500, John Grehan wrote:

>>'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.
>
>On this we can agree to disagree. Croizat referred to character
>recombination as a process and described it as such. Others can make their
>own choice on this.

OK - I agree I may have misread that. So we do agree (I think) that to
Croizat hybridization and "character recombination" are two completely
separate evolutionary processes.

>>I suppose "differentiated ancestor" is a typo for "undifferentiated
>>ancestor"?
>
>No - I was indeed referring to a differentiated ancestor in that the
>ancestor has already differentiated geographically before the development
>of distinct descendant lineages.

Thanks for the clarification. I find indeed that Croizat is very emphatic
about this - I wonder why? Why does it seem to be so essential for
panbiogeography to assume that ancestors (and their ancestors, "and so on
into geological time unbound") are already differentiated? It seems to be
"unpanbiogeographical" to entertain the notion that differentiation sets in
after separation. Or am I again misreading something?

>>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.
>
>No worries.
>
>>>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.
>
>Meaning?

That after finding you refer to your "impressions" twice in a single
posting,  I begin to suspect  that a whole field (panbiogeography) is based
on principles which now turn out to be no more than "impressions" gained
after reading Croizat.

>>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).
>
>For some maybe so. For others maybe not. Maybe Darwin takes the cake for
>having the greatest amount of controversy over what he did or not mean or
>did or not say - even entire books on the question.

Anyone who has ever read the Origin (and Croizat) will be able to judge for
themselves whether the comparison is appropriate.

>>>I don't know about 'any number'
>>My impression was that Croizat did not restrict character recombination to
>>any specified number of characters.
>
>But on the other hand he did not say that there was not a restriction. His

Would he have omitted it if he believed there *was* a restriction to the
number of characters that could recombine within the set of "ancestral"
characters (the "bank" of switches)? And he is unusually clear in that he
believes that the number of switches on the "bank" is constant and does not
change much over time.

Peter