Comment on An apology to PUC by Sean Pitman.

@OTNT_Believer:

In all of these cases you refer to the DNA divergences or similarities were not used to define these taxa. In each case the biological species concept was employed.

“The biological species concept defines a species as members of populations that actually or potentially interbreed in nature, not according to similarity of appearance. Although appearance is helpful in identifying species, it does not define species.”

http://evolution.berkeley.edu/evosite/evo101/VA1BioSpeciesConcept.shtml

The problem with this “biological definition” of species is that it is based on reproductive isolation – a feature that is not universally applied. Great Danes and Chihuahuas are arguably “reproductively isolated” yet are still classified within the same species group. Also, when it comes to “cryptic species” the isolating factor may be geographic rather than genetic. Functionally and phenotypically speaking, certain cryptic species would be indistinguishable. They would also be able to mate and produce both viable and fertile offspring.

So, it is very hard to argue that cryptic species would be easily identifiable as “species” without knowledge as to their separate geographic distribution and underlying functionally-neutral genetic divergence.

I have no problem with your functional difference ideas, I just disagree on your use of such ideas. We have a well functioning definition of species used by mainstream taxonomists, and trying to replace it with another equally problematic species concept that is used by no one else but a few creationists just further marginalizes any potential for discussion with mainstream taxonomists.

I think it rather difficult to marginalize creationists or design theorists further than they’ve already been marginalized by mainstream scientists. There is a deep seated fundamental disagreement over the creative potential and limits of RM/NS. Until this basic dividing line is crossed, there will be no general agreement over differing concepts as to either the origin or basic dividing lines between different “kinds” of living things.

i think I understand the point you are trying to make with functional difference being the dividing line between “created types” and variation within a created type. This is essentially the point that [B]rand is making with his term megaevolution. So why not at least work within the framework of what other creationinists already have defined? Even Behe and Demski have defined these kinds of boundaries, basing them on irreducible comlexity arguments.

The reason I don’t like the general use of the term “macroevolution” is because it is used to include what Brand and other creationists and IDists would describe as requiring the outside input of Intelligent Design. Macroevolution is not generally qualified as to type. That is why I’m trying to get people to actually qualify what they mean, specifically, when they use the term “macroevolution”… especially in the context of a discussion over the potential and limits of evolutionary progress.

You may not like the biological species concept, but just tossing it out and substituting it with a functional difference requirement only adds a different problem, and since no one else uses this definition of species, you have no common ground for discussion. According to you reasoning Darwin’s finches are not separate species at all and in fact are conspecific with other members of the “domed-nest clade.”

They aren’t clearly part of a separate gene pool from other members of the “domed-nest clade”. In other words, I wouldn’t be at all surprised if the Darwin Finches could interbreed and produce viable and fertile offspring with other members of this clade.

So, when someone like you comes along and argues that Darwin’s Finches are so dramatically different from everything else that they are difficult to explain over the course of a few thousand years, I have to scratch my head and wonder as to the reason for such an assertion?

It seems so much more resonable to consider Darwin’s Finches as simply separate species, as recognized by all taxonomists, and as an example of macroevolution, as defined by evolutionary theory. Then, ala Brand, consider birds and reptiles as separate classes (or even part of the same monophyletic group) and as an example of megaevolution. This makes it then a lot easier for me as a creationist to say that I accept the more limited definition of macroevolution that formed the different kinds of domed-nest builders, but reject the megaevolutionary process proposed to have been the mechanism whereby birds evolved from reptilian ancestors.

It makes it even easier to explain, specifically, why one believes that there are obvious creative limitations to the RM/NS mechanism. If you can’t do this, it really makes no sense for you or me or anyone else to argue that various forms of “macroevolution” are possible, but not “megaevolution”. If you don’t know why there should be such a distinction, you really don’t have much of an argument…

Of course, for me personally, I haven’t yet figured out where the lines should be drawn between macro- and megaevolution. I certainly don’t think birds evolved from reptiles, so that is megaevolution, but what about hummingbirds vs. sunbirds?

If you haven’t figured out where the lines should be drawn, or why they should be drawn at all, upon what do you base your belief that such a line probably exists?

I think a line exists because I think I know the statistical cut-off point beyond which RM/NS becomes completely untenable this side of a practical eternity of time. Otherwise, I wouldn’t have a rational reason to propose any kind of limitation for evolutionary potential…

I think there is enough work to be done using these more compatible concepts, so can’t we just use them and quit quibbling over what a species is and leave that to taxonomists?

These “quibbles” will end up changing the basis of taxonomy if basic concepts such as “irreducible complexity” and limits to evolutionary progress based on “levels of functional complexity” are ever accepted by mainstream scientists…

These quibbles also help to clarify what one means when one uses words like “macroevolution” – a word that is often used, by mainstream scientists, to cover everything from neutral genetic differences (evolved due to geographic isolation in certain groups within the same functional gene pool) to the functional differences between reptiles and birds…

Sean Pitman
www.DetectingDesign.com

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