Review of The Structure of Evolutionary Theory

I threatened I would do this. But seeing Gould's book on the general science section on the shelves of Barnes & Noble decided it for me. I feel I must warn the general public: If you are not a professional biologist, you are absolutely barking mad if you are thinking about reading this book.

It's not because the book is big (so obviously so that it's impossible not to mention it), or because it's boring (it isn't). It's just because this book is not aimed general readers, not even well-informed ones. Gould doesn't define a lot of the technical terms he uses. (Know what anagenesis is? How about formalism or internalism?) He even makes the occasional comment like, "And we know how the data for that turned out." And sure, I know what he's referring to, because I'm a professional biologist with an interest in evolution -- but it's the sort of comment that seems designed to frustrate a casual reader.

I suspect many copies sold in general bookstores will be left on shelves, unread, as a subtle ad to convince friends and visitors of how smart the buyer is. (Many people explain how Stephen Hawking's A Brief History of Time spent so long on the bestseller lists this way.)

That said, because I think this book is interesting and important -- people will be discussing it for years, literally -- it's good for those of us who've read it to try to summarize and comment on it.

So here we go.

In Chapter 1, Gould has two contentions. First, there are three basic things Darwin proposed that make natural selection an important and powerful theory. Second, all three of those basic ideas have been substantially expanded by recent research. Darwin wasn't wrong about natural selection, but it is not the whole story. I'll paraphrase Darwin's idea in bold and the expansion that Gould suggests after in italics.

1. Natural selection works on individuals.

Selection occurs at many levels. In particular, punctuated equilibrium implies that selection of species occurs and is important for macroevolutionary patterns.

2. Selection for small, adaptive features in organisms is the major source of evolutionary change.

There are limits to how much organisms can change over time.

3. There was nothing special about the past. We can use what happens around us today to extrapolate what happened in distant yesterdays.

Sometimes, a really big rock falls out of the sky.

Gould spends the rest of the book's first half exploring historical ideas about evolution. Gould is clearly in his element here, and the scholarship is impressive. In fact, it comes out that Gould owned many key books. Several pictures were taken from his own collection of antique books, some of which had never been published before.

Chapter 2 discusses (or, to borrow one of Gould's stylistic tics, "presents an exegis of") Darwin's Origin of Species. Considering that Origin of Species is one of the most famous books in science, is it worth it? "Darwin said..." gets said a lot in biology. Gould's agrees that Darwin said many things, but makes it his mission to disentangle comments made in passing versus the major themes that Darwin revisited over and over.

Subsequent chapters discuss the historical counterclaims to Darwin's three major ideas. Gould is not aiming to revive these older criticisms of Darwinism, but he clearly does want to show that the expansions to evolutionary theory he's discussing have a long and serious intellectual history.

Chapter 3 discusses point 1, above (individual vs. hierarchical selection).

Chapters 4 and 5 focus on point 2 (which Gould variously typifies as "functionalism vs. formalism," or "externalism vs. internalism." He never clears up the difference between these terms, if he intends one). I found these to be quite fascinating. Gould points out that there was a long tradition of treating the evolution of species the same way as the development of individual organisms. Some workers went so far as to argue that species had predictable stages of birth, development and growth, and inevitable weakening and death.

Chapter 6 looks at geology, and how strongly the idea of uniformity of events impressed itself on Darwin (point 3 above).

Chapter 7 covers the so-called "Modern Synthesis" of the mid-20^th century. Gould emphasizes how utterly confident researchers at the time were in the all-powerfulness of natural selection, and in the completeness of natural selection as a theory.

Chapter 8 leads the second half of the book, and it's a lengthiest slice, laden with digressions. The Table of Contents entry for this chapter alone spans almost three pages! You might call this the "punctuated equilibrium" chapter: punctuated equilibrium clear has pride of place in Gould's efforts to develop a theory for species selection. Gould freely and frequently admits his bias: after all, he developed the idea of punctuated equilibrium with Niles Eldredge.

Gould spends many pages examining studies designed to provide evidence (pro or con) for punctuated equilibrium, and concludes that punctuated equilibrium occurs at relatively high frequencies. This is a major starting point from which Gould develops a hierarchical theory where natural selection can occur at any biological level, from the small to the large.

This chapter is simultaneously fascinating and frustrating, because it is so personal for Gould. Gould does not mince words in describing how biologists responded to punctuated equilibrium. He claims that some of the controversy around the idea was due to professional jealousy on the part of some colleagues. On the other hand, I could have done without the long sections where Gould examines how others have used or misused the idea of punctuated equilibrium outside biology. While it's hard to criticize digressions in such a huge volume, laden with footnotes that span multiple pages, these sections have little to do with the book's self-declared purpose.

Where are we again? Ah, Chapters 10 and 11. I group these two chapters together because they are both concerned with the ideas that there are constraints upon natural selection, and that not every biological feature is an evolutionary adaptation.

I also think of Chapter 10 and 11 and "the spandrels chapters." What's a spandrel? Biologists probably know (or know about) a paper co-written by Gould (with Richard Lewontin), partially titled "The spandrels of San Marco." For you non-biologists – or non-architects – a spandrel is a bit of architectural space. Specifically, when you put two arches next to each other, there's going to be a space between them. You can use that roughly triangular space for decoration, although the space wasn't made for decoration. Gould and Lewontin argue that many features in living organisms are spandrels: they weren't custom made for anything (just as architectural spandrels weren't made for decoration), they were just conveniently... well... there for other reasons. The idea of that biological spandrels are commonplace expands traditional Darwinism, argues Gould, because in most conventional Darwinian explanation, pretty much everything is argued to be "custom made;" that it, every feature has some sort of adaptive function.

These two chapters also has Gould discussing recent developments in genetics, which showed that regulatory genes that control some aspects of growth have stayed more or less the same in a wide variety of animals for a very, very long time. This was a startling finding, because Darwinians argued that given time, almost everything would have been fine-tuned and replaced through natural selection. This field, as Gould himself admits, is moving so fast that this chapter is probably going to be outdated before any of the others.

Almost done...

Chapter 12 is relatively short. It asks, "Doe the processes driving evolution stay the same throughout evolutionary time?" Darwin counted on that fact. Gould argues that the answer is "No," citing as his major example that we now have a prime candidate for the extinction of the dinosaurs: a meteor hit the earth and upset the applecart. A meteor strike is sufficiently unusual that it can't be counted as a routine event, but it definitely had an important impact on the face of life on this planet. Gould notes, though, that although the planet has had several mass extinctions, it doesn't seem that meteor impacts explain any extinction except the one at the end of the Cretaceous. So, while Gould applauds the fruitful science that lead to the discovery of the meteor impact, he does seem wistful that it hasn't led to a more wide-ranging theory.

The final epilog (which Gould calls, "honest to God, a true end to this interminable book") is quite affecting. Gould pays tribute to his hero, Charles Darwin, in a moving way. Gould writes that even without Darwin, biologists would have a theory of evolution – eventually. But, "we would have experienced the same biological revolution without the stunning clarity… of a complex central logic so brilliantly formulated(.) In this alternate world, we would probably be honoring a different and far less compelling founder by occasional visits to a statue in a musty pantheon, and not by constant dialogue with a man whose ideas live, breath, challenge, taunt, and inspire us every day of our lives, more than a century after his bones came to rest on a cathedral floor..."

We were pretty lucky to have Darwin, Gould says.

And we were pretty lucky to have Gould, too. While there are lots of criticisms to be launched The Structure of Evolutionary Theory (particularly that some editor should have reigned in Gould's excesses), the ideas presented within will be rich grounds for discussion for years to come.