Since it has repeatedly been claimed here by several people that there are no significant disputes about mechanism among evolutionary theorists (i.e., that all disputes are only over minor details or issues “on the periphery”), I offer here a clear example of a serious dispute regarding mechanism between evolutionary biologists.
This is a review by Jerry Coyne of an article by Davidson and Erwin. The review is published in Science, a prestigious journal.
The point here is not which side in the dispute is correct; the point is that there is a dispute, that the dispute is over mechanisms of evolution, and that it is not a dispute over a trivial “detail” question or a “peripheral” question but over a major difference regarding the causes of evolutionary change at the higher taxonomic levels.
Which is what I said an earlier discussion to Chris Falter – that such disputes exist. He seemed to contest this.
I could provide many more debates of this sort, but I don’t intend to waste my time digging them all up. (The sort of person here who will not accept this example as proof of the existence of serious disagreement over evolutionary mechanisms would not accept any other example I could dig up.)
For people who are interested in the broader questions behind this dispute, there is an informative article by Erwin:
For what it’s worth, the position advanced by Davidson and Erwin in their 2006 review (evolution of animal body plans through assembly of gene regulatory network “kernels” in a process disctinct from “microevolutionary patterns”) is identical to that which Erwin advanced with James Valentine in 2013, in which they wrote:
“One important concern has been whether the microevolutionary patterns commonly studied in modern organisms by evolutionary biologists are sufficient to understand and explain the events of the Cambrian or whether evolutionary theory needs to be expanded to include a more diverse set of macroevolutionary processes. We strongly hold to the latter position.”
Erwin D.H. & Valentine J.W., 2013, The Cambrian Explosion: The Construction of Animal Biodiversity, p. 10; my emphasis
It’s not “minor” when one evolutionary theorist suggests that different mechanisms operate at different taxonomic levels, and another denies it. For more background, see the other article I referenced.
You’re changing the goalposts. Whether or not an observation is useful and whether or not it is true are two different things. Is it true or false that evolutionary theorists sometimes have major disputes about mechanisms?
If you think it’s minor, you know less about evolutionary theory than you think you do. I suggest you sit down and read Gould’s Structure of Evolutionary Theory, or at least large chunks of it. You clearly lack a big-picture framework when you talk about evolution.
I read the article and saw no mentions of mechanisms. If you think I am wrong, then quote the paper. For example:
So what is the mechanism of “architectural alterations”? How do they differ from the standard types of mutations that are already a part of the theory? It would seem that genetic recombination is more than adequate for producing these changes. It isn’t clear at all how Davidson and Erwin are proposing anything different from standard microevolutionary events.
They’re not, in the sense that all the changes they’re talking about are ultimately caused by single-nucleotide mutations, gene duplication, etc. The difference is that Davidson and Erwin are thinking about developmental/morphological change at different hierarchical levels, and point out that only studying one level (microevolution/speciation) doesn’t necessarily tell us everything about the other levels. The mechanisms of genetic change are the same, just the effects and how they relate to morphology might be very different.
I think this is generally true, but like Coyne, I’m a bit skeptical about how this can be applied to our man-made classification system. I don’t think it’s as clear-cut as Figure 3 of Davidson and Erwin’s paper might suggest.
“In their review of the evolution of animal
body plans, Davidson and Erwin (1) proposed
that the origin of higher level clades,
such as phyla, involves mechanisms other than the normal microevolutionary processes thought to cause speciation.”
Isn’t the word “mechanisms” in the most pronounced possible place – the first sentence of the article – for you to notice it? To help you, I have employed boldface and italics.
Doesn’t the placement of that statement in the first sentence of a short review article suggest that the article will have something to do with mechanisms?
And doesn’t Coyne go on to dispute the claim about mechanisms?
Sheesh. If this is how well science researchers can understand what they read, something is very lacking in science education.