Brief thoughts on The Structure of Evolutionary Theory

I just passed the 325-page mark in Gould's The Structure of Evolutionary Theory, which puts me in the middle of chapter 4. Chapter 1 was perhaps the most difficult, the abstracts at the end of the opening section being a bit cumbersome. Once I got into chapter 2, however, the sailing was a little smoother, and by Chapter 3 Gould hits his stride. Whatever complains I might have about the style or need for editing aside, I am getting quite a lot out of this book. I'm curious to see how Gould unveils his hypothesis for hierarchical selection in the later chapters, but as far as the historical accounts that make up so much of the early chapters are concerned I feel like an intellectual weight has been lifted from my shoulders.

In many (if not most) books I've read that mention scientific figures of centuries past like Richard Owen and Georges Cuvier, what Gould called the "textbook cardboard" in Time's Arrow, Time's Cycle has been so pervasive that it's difficult to come away with an understanding of these researchers that even closely resembles reality. Indeed, Richard Owen has often been cast as Darwin's arch-nemesis, yet as I read the standard stories I knew that things weren't quite right. Gould's historical approach of considering the formalist vs. functionalist debate has helped to clear up some of my confusion.

Everybody knows that the book Natural Theology by William Paley had a profound impact on Charles Darwin, but like much of what "everybody knows," there are important details that have generally been overlooked. Paley's writing represented what Gould deems the "British-school" of adaptationism (or functionalism), the perfect meshing of organisms into their environment reflecting the attributes of God (the theological aspect of this has long been abandoned, but the basic tradition still has roots in natural theology). Beyond being well-acquainted with the work, Darwin seemed to construct his own abstract about the power of natural selection with Paley's book in mind, directly refuting some of the examples Paley tried to marshal for his own argument (i.e. the eye).

Earlier, and in France rather than England, Georges Cuvier took a sort of "grade" view to classification and created four great embranchments into which animals could be grouped. The basis for this system involved the adaptations of organisms, one aspect providing the key to the rest (i.e. if you found a sharp claw, you could infer that it belonged to a carnivore and then reasonably reconstruct what the rest of the animal might have been like by inferring a meat-eating habit). Geoffrey St. Hilaire, Cuvier's noted nemesis, stepped on Cuvier's toes by attempting to unify all the embranchments into one group via the use of an archetype. Under Geoffrey's vision, for instance, insects were organisms that were almost walking vertebrae, the body within the exoskeleton representing a vertebra with the jointed legs being homologous with vertebrate ribs! This was the formalist view,* and even though Richard Owen would be known as the "British Cuvier" he was more influenced by the ideas of Geoffrey than the anatomist he was so often compared to.

*I don't especially like the term "formalist," especially since I have to mentally emphasize the "form" part of the word so that images of tuxedos don't creep into my mind. I can't think of a better one to replace it with, though, and my own mental diversions are no reason to suggest picking something else in any case.

As with Geoffrey, vertebrae seemed to hold the key for Owen, the entire vertebrate skeleton seemingly arising from a vertebral archetype. Even though Owen's book On the Nature of Limbs (which has recently been republished) would lead the book-browser to believe that it primarily addresses the homologous and analogous features of limbs, it actually represents an attempt to reconcile the problem of illustrating how limbs were only modified parts of a vertebra.

Given this richer historical picture, Darwin and Owen were essentially playing out the much older functionalist vs. formalist debate that Cuvier and Geoffrey were more famously known for, and while evolution certainly played an important role it does not seem that Owen's opposition to Darwin emerged only from a disagreement over evolution in general. When viewed in this context, then, the question of evolution seemed to be nested within a much older debate, Darwin breaking away from the functionalist English position (while still remaining within it) by stressing the evolution of organisms by natural selection. Everyone may have their favorite heroes and villains in these scientific sagas, but what I appreciate about Gould's book is the in-depth look at shifting views (even if they were often considered polar opposites rather than parts of a whole).

Spending so much time on historical context might seem excessive or unnecessary to some readers, but I think it allows the reader to more fully understand the connections between so many researchers involved in a debate that (to perhaps to a lesser extent) is still going on today. Rather than being directly opposed as two distinct ways of understanding evolution, constraint (formalism) and adaptation (functionalism) are intertwined, each being important to the study of evolution. This general dichotomy might not cover all aspects of present study or debate, but constraints imposed by development, history, etc. are still as important to understand as what selection pressures might drive adaptation. Gould definitely has an axe to grind in this area, his history being of great importance to his book as he seems to be using it to set some historical background for his own ideas, but I do think that issues surrounding constraint vs. adaptation remain. As Razib notes (see link below), other historians might have covered the same ground as Gould has as far as what I've discussed here, but being that I had not encountered such perspectives before I found Gould's account to be very stimulating. I've still got a long way to go, but if the number of hastily scribbled notes I've affixed to the pages is any indication, Gould's massive tome has definitely provided me with ample food for thought.

[Update: Razib has a brief post citing a snippet from John and myself. I've added a new snippet of text to the original post to clarify something I felt might have been overlooked in the cutting and pasting.]

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