pz

And there's the rub...the current neo-Darwinian model, the one used by population biologists, is incomplete and inadequate. It's not wrong, it just doesn't appropriately describe a wide set of phenomena, for which we need new syntheses. The division doesn't exist in the eyes of many scientists because the conceptual tools aren't in their hands to work with it -- which doesn't mean the division is not real.Would you really argue that the difference between chemistry and biology is simply artifactual? You carry reductionism too far. I think there are novel phenomena that emerge at higher levels, that cannot be predicted or analyzed with the toolset of the lower level.

Macroevolution has its own unique principles, which do not violate but must be an extension of the rules of microevolution. Similarly for biology from chemistry, and chemistry from physics, and physics from mathematics. Your argument would be the same as sweeping away all the sciences and just calling them all math.
I don't think so. The death of an organism has different implications and different effects on evolution than cellular necrosis or apoptosis, and usually has different causes. We don't call that distinction an empty artifact, I hope.

pz

About faust's counterarguments:

I don't like them much at all. I think it is an absolutely horrible mistake to accept at the outset the definitions of micro and macro evolution offered by malachi256. Those are simply bad definitions. The only reason to accept them is that they are so awful, that they destroy his argument -- but then that reduces the whole debate to a rhetorical game, rather than discussing the substance of the biology.

Rufus has just listed definitions that are much, much better. If one wants to argue over those, then one is getting into the real definitions used by biologists, rather than that weird pair of useless rationalizations held only by malachi256.

Faust does make the good point farther on that since time isn't a factor in the Bizarro World definition of macroevolution, the whole creationist argument of insufficient time is meaningless. However, we could punch holes all day in that sloppy mess of contradictions -- one more doesn't matter if one "accepts" them in the preliminaries of the debate.

I'm not sure why anyone would waste time with the pedagogical excuses malachi256 offered. They aren't practical. The whole bioinformatics detour is a red herring -- it contributes nothing to the question at hand. And why in the heck would one start digging into genetic simulation programs? What's the relevance?

I really feel that the whole shebang is disintegrating into incoherence, largely due to the focus on a poor question and the acceptance of useless, nonstandard definitions. This is not a debate that will produce useful ideas, not at this rate, at least.

Doubting Didymus

I knew that this was going to happen, as soon as I read malachis proposed definitions.

I emplore the participants of the debate to stop using the words 'macroevolution' and 'microevolution' to describe the things you're talking about. The meanings of those words are already far too confused and nebulous even in the field of biology, and using them to describe things that really have nothing to do with any definition I know of is going to do nothing to remedy the situation. You're arguing unproductively. A win on either side is going to be meaningless. Think what such a win will be, translated into simple english:

"I [won/lost]! The distinction between macro and micro evolution (here defined in a way that has never been used by any biologist in the field and will never be used again by anyone bar we two debate participants) [is/is not] scientifically useful."

What would that mean, using either alternative? Sod all.

I have a serious request, though it may be inappropriate to enstate it halfway through: Ignore the macro / micro words and focus on what you two are actually debating about, which isn't macroevolution at all, but is this: "is it scientifically reasonable to divide evolution into two categories: evolution that produces small morphological changes in populations and evolution that produces large morphological changes." Thats what you're really arguing about, not macroevolution vs microevolution, and it is a very good idea to make that as clear as possible, as there IS a worthwhile and interesting debate to have over macro and microevolution as they are defined by evolutionary biologists, and the debate you're having isn't it.

RufusAtticus

During my writtens last week I wrote about how developmental biologists think that neo-Darwinism is incomplete; although, I didn't find a reference to exactly how it was incomplete. I'm interesting in hearing from you about this incompleteness.

Okay. What principles are unique to the divergence between species that are not found in the divergence within a species?

Well, the death of an organism is the result of the cumulations of cellular deaths. Similarily the death of a species is the result the cummulation of the death o its members. Parralleling the common statement that macroevolution is lots of microevolution, why can't extinction be explained by lots of death?

Doubting Didymus

If I want to explain why an organism died, I don't say "Well, that'll be the cumulative effect of cell deaths, that will". Technically, I suppose it's true, but to actually explain the death I need to examine the things that actually killed the organism. Similarly, there are factors that cause the extinction of a species that surely can't be explained just by saying that lots of the individuals in that species died.

Dr.GH

There is ample recognition of mass extinctions that are related to events unrelated to selection. There are no means that I can think of for a meteor strike every 100 million years or so to become an effective selector.

The rapid species radiation following these mass extinctions suggests to me that "punk ek" is more a emperical generalization than a well developed theory. If there is a stable enviornment, there will be stable species, in disrupted environments there will be new species. The adaptive range of a species is finite, because the genetic variation within what we call a species is finite. Taking reproductive success as the criteria of "species" tells us that, as infinite adaptation can not occurr without the accumulation of infinite genetic variation, species radiation will be more common in diverse environments. Genetic Drift is not particularly selection driven, so vast environments can yield non-selection driven speciation. Founder effects magnify drift, and can be nonselection driven (eg bird songs as reproductive cues).

This makes the notions of micro- and macroevolution hard to elliminate, even as just shorthand for how high up the phylogenetic tree you are making an argument (the most common use I read in biology).

The problem in the creato war is that creatos distort what these terms mean, arguing that there is a fundament kind of "microevolution" that is differnt from "macroevolution." But, they also claim that there was a global flood 4K years ago, and that the universe is 6K years old. They believe in talking animals, talking bushes, talking clouds and alot of other really stupid things.

Lobstrosity

Right, it seems to me that the creationist's key problem in this regard is making the claim that macroevolution is synonymous with "up-hill" change and "information increase," which as we all know is expressly forbidden by every branch of science known to man (for the sarcastically impaired, this is sarcasm). Microevolution, on the other hand, is merely the selective loss of information due to fall-related deterioration and is thus fine. Obviously these two ad hoc assertions are completely erroneous and only serve to put us on the defensive with regards to the terms macro- and micro-evolution when there are legitimate distinctions that can be made and where there is valuable insight to be gained.

Dr.GH

It would be interesting to learn just which peabrain came up with this false dichotomy.

notMichaelJackson

Why did they set a one day time limit between responses? This certainly wouldn't be enough time for most to arrange a response to a serious debate, and the debators seem to be having trouble with it.

pz

There are a number of reasons why the current theory of evolution should be regarded as incomplete. The central one is that while "nothing in biology makes sense except in the light of evolution", some important disciplines within biology, development and physiology, have only been weakly integrated into the theory.

Raff (1996) in his book The Shape of Life gives some of the historical reasons for the divorce of evolution and development. One is that embryologists were badly burned in the late 19th century by Haeckel, who led them along the long and unproductive detour of the false biogenetic "law". That was a negative reaction; there was also a positive stimulus, the incentive of Roux's new Entwicklungsmechanik, a model of experimental study of development that focused exclusively on immediate and proximate causes and effects. Embryology had a Golden Age of experimentation that discouraged any speculation about ultimate causes that just happened to coincide with the time that the Neo-Darwinian Synthesis was being formulated. Another unfortunate instance of focusing at cross-purposes was that the Neo-Darwinian Synthesis was fueled by the incorporation of genetics into evolutionary biology...and at the time, developmental biologists had only the vaguest ideas about how the phenomena they were studying were connected to the genome. It was going to be another 50 years before developmental biology fully embraced genetics.

The evolutionary biologists dismissed the embryologists as irrelevant to the field; furthermore, one of the rare embryologists who tried to address evolutionary concerns, Richard Goldschmidt, was derided as little more than a crackpot. It's an attitude that persists today. Of course, the problem is mutual: Raff mentions how often he sees talks in developmental genetics that end with a single slide to discuss evolutionary implications, which usually consist of nothing but a sequence comparison between a couple of species. Evolution is richer than that, just as development is much more complex and sophisticated than the irrelevant pigeonhole into which it is squeezed.

In her book, Developmental Plasticity and Evolution, West-Eberhard (2003) titles her first chapter "Gaps and Inconsistencies in Modern Evolutionary Thought". It summarizes the case she makes in the rest of her 700 page book in 20 pages; I'll summarize her summary here, and do it even less justice.

She lists 6 general problems in evolutionary biology that could be corrected with a better assimilation of modern developmental biology.

• The problem of unimodal adaptation. You can see this in any textbook of population genetics: the effect of selection is to impose a gradual shift in the mode of a pattern of continuous variation. Stabilizing selection chops off both tails of the distribution, directional selection works against one or the other tail, and disruptive selection favors the extremes. This is a useful, productive simplification, but it ignores too much. Organisms are capable of changing their specializations either physiologically, in the form of different behaviors, morphologies, or functional states, developmentally in the form of changing life histories, or behaviorally. Evolution is too often a "theory of adults", and rather unrealistically inflexible adults at that.
• Cohesiveness. There is a long-standing bias in the evolutionary view of development, that of development imposing constraints on the organism. We can see that in the early favor of ideas like canalization, and the later vision of the gene pool as being cohesive and coadapted, which limits the magnitude of change that can be permitted. It's a view of development as an exclusively conservative force. This is not how modern developmental biologists view the process. The emerging picture is one of flexibility, plasticity, and modularity, where development is an innovative force. Change in developmental genes isn't destructive -- one of the properties of developmental systems is that they readily accommodate novelty.
• Proximate and ultimate causation. One of the radical secrets of Darwin's success was the abstraction of the process away from a remote and unaccessible ultimate teleological cause and to a more approachable set of proximate causes. This has been a good strategy for science in general, and has long been one of the mantras of evolutionary biology. Organisms are selected in the here and now, and not for some advantage many generations down the line. Evolutionary biology seems to have a blind spot, though. The most proximate features that affect the fitness of an organism are a) behavioral, b) physiological, and c) developmental. These are the causes upon which selection can act, yet the focus in evolutionary biology has been on an abstraction at least once removed, genetics.
• Continuous vs. discrete change. This is an old problem, and one that had to be resolved in a somewhat unsatisfactory manner in order for Mendelian genetics (an inherently discrete process) to be incorporated into neo-Darwinian thought (where gradualism was all). Many traits can be dealt with effectively by quantitative genetics, and are expressed in a graded form within populations, and these are typically the subject of study by population geneticists. We often see studies of graded phenotypes where we blithely accept that these are driven by underlying sets of graded distributions of genes, such as the studies of Darwin's finches by the Grants, yet those genes are unidentified. Conversely, the characters that taxonomists use to distinguish species are usually qualitatively distinct are at least abruptly discontinuous. There is a gap in our thinking about these things, a gap that really requires developmental biology. Wouldn't it be useful to know the molecular mechanisms that regulate beak size in Darwin's finches?
• Problematic metaphors. One painful thing for developmental biologists reading the literature of evolutionary biology is the way development is often reduced to a metaphor, and usually it is a metaphor that minimizes the role of development. West-Eberhard discusses the familiar model of the "epigenetic landscape" by Waddington, which portrays development as a set of grooves worn in a flat table, with the organism as a billiard ball rolling down the deepest series. This is a model that completely obliterates the dynamism inherent in development. Even worse, because it is the current metaphor that seems to have utterly conquered the imaginations of most molecular biologists, is the notion of the "genetic program". Again, this cripples our view of development by removing the dynamic and replacing it with instructions that are fixed in the genome. This is bad developmental biology, and as we get a clearer picture of the actual contents of the genome, it is becoming obviously bad molecular biology as well.
• The genotype-phenotype problem. Listen to how evolutionary explanations are given: they are almost always expressed in the language of genes. Genes, however, are a distant secondary or tertiary cause of evolutionary solutions. Fitness is a collective product of success at different stages of development, of different physiological adaptations, and of extremely labile interactions with the environment. Additionally, a gene alone is rarely traceable as the source of an adaptive state; epigenetic interactions are paramount. We are rarely going to be able to find that a specific allele has a discrete adaptive value. It's always going to be an allele in a particular genetic background in a particular environment with a particular pattern of expression at particular stages of the life history.

One unfortunate problem with discussing these issues in venues frequented by lay people is, you guessed it, creationism. Any criticism of a theory is seized upon as evidence that the theory is wrong, rather than as a sign of a healthy, growing theory. The Neo-Darwinian Synthesis is not wrong, but neither is it dogma. It was set up roughly 70 years ago with the knowledge that was available at the time, and it is not at all surprising that the explosion of new knowledge, especially in molecular biology, genetics, and developmental biology, means that there are radically different new ideas clamoring to be accommodated in the old framework. The theory is going to change. This isn't cause for creationists to rejoice, though, because the way it is changing is to become stronger.