I just finished Sean B. Carroll’s Endless Forms Most Beautiful: The New Science of Evo-Devo the other day, and I must confess: I was initially a bit disappointed. It has a few weaknesses. For one, I didn’t learn anything new from it; I had already read just about everything mentioned in the book in the original papers. It also takes a very conservative view of evolutionary theory, and doesn’t mention any of the more radical ideas that you find bubbling up on just about every page of Mary Jane West-Eberhard’s big book. One chapter, the tenth, really didn’t fit in well with the rest—the whole book is about pattern, and that chapter is suddenly talking about a few details in the evolution and development of the human brain.
So I read the whole thing with a bit of exasperation, waiting for him to get to the good stuff, and he never did. But then after thinking about it for a while, I realized what the real problem was: he didn’t write book for me, the inconsiderate bastard, he wrote it for all those people who maybe haven’t taken a single course or read any other books in the subject of developmental biology. I skimmed through it again without my prior biases, and realized that it’s actually a darned good survey of basic concepts, and that I’m going to find it very useful.
Take, for instance, chapter 5, titled, “Dark Matter of the Genome: Operating Instructions for the Toolkit”. It’s a simple overview of regulatory logic, explaining what regulatory regions are, describing the kinds of logical operators to which they correspond, and bringing in the idea of genetic switches and modules. This is difficult stuff to teach; I generally charge in with specific examples and try to draw out some general understanding by showing the details. But on reading this, I see a better way. I’m going to have to model a lecture on this chapter and ease students in with an overview of the big picture (in other words, I am so stealing Carroll’s work).
He also does an excellent job of tying together paleontology and development, explaining how the concepts of modularity and genetic switches that he’d just covered are not just useful for understanding how butterflies get spots on their wings, but also makes the transformations we observe in the fossil record more comprehensible. Why are developmental biologists suddenly getting so interested in evolutionary biology? Because for the past 100+ years, we’ve been building a conceptual toolkit for analyzing embryos, and we’ve just recently noticed that applying those tools to evolutionary questions gives us a powerful perspective.
The final chapter is simply excellent, and carries a message I try in my own clumsy way to communicate, too. It has two themes: “Evo Devo as a Cornerstone of a More Modern Synthesis”, in which he explains how developmental biology is inspiring a revolution in evolutionary thinking, and “Evo Devo and Teaching Evolution”, where he discusses how this interdisciplinary mode of thinking helps us understand biology better. He also addresses the battle with creationists, and is appropriately dismissive of their pseudoscientific claims while warning us all to wake up to their political shenanigans.
Here’s an excerpt from the section on teaching evo devo. It might irritate some of the evolutionary traditionalists, but I think he has many good points here.
The evolution of form is the main drama of life’s story, both as found in the fossil record and in the diversity of living species. So, let’s teach that story. Instead of “change in gene frequencies,” let’s try “evolution of form is change in development.” This is, of course, a throwback to the Darwin-Huxley era, when embryology played a central role in the development of all evolutionary thought. There are several advantages of an embryological approach to teaching evolution.
First, it is a small leap to go from the building of complexity in on generation from an egg to an adult, to appreciating how increments of change in the process, assimilated over greater time periods, produce increasingly diverse forms.
Second, we now have a very firm grasp of how development is controlled. We can explain how tool kit proteins shape form, that tool kit genes are shared by all animals, and that differences in form arise from changing the way they are used. The principle of descent by modification (of development) is clear.
Third, an enormous practical advantage is the visual nature of the Evo Devo perspective. The Chinese proverb I cited in chapter 4, “Hearing about something a hundred times is not as good as seeing it once,” is sound educational doctrine. We learn more by combining visuals with text. Let’s show the students embryos, Hox clusters, stripes, spots, and the glory of making animal form. The evolutionary concepts follow naturally.
A fourth benefit of this approach is that it brings genetics much closer to the powerful evidence of paleontology. Dinosaurs and trilobites are the poster children of evolution, and they inspire the vast majority of those who touch them. By placing these wonders of the ancient past in a continuum from the Cambrian to the present, life’s history is made much more tangible. It would indeed be a wonderful world if every student had guided, repeated classroom contact with some fossils.
If you’re a developmental biologist, this book may make you snooze. But if you’re anyone else, I recommend Endless Forms Most Beautiful highly—this is the primer that will bring you up to speed on the basics of evo devo in a pleasant way. It’s full of butterfly wings and zebra stripes and exotic arthropods and molecules in stripes, and along the way you learn a fair bit of developmental biology.
I’ll add that in the few years since I reviewed this book, I’ve used it as an auxiliary text in my developmental biology classes. The students have been generally positive about it, but they also haven’t found it easy going, especially the middle section which emphasizes the conceptual issues of developmental gene regulation. I’ll be using it again, though, because even though it may be hard to grasp and is surprisingly novel to students’ thinking, it’s still an essential collection of ideas that they must understand to be able to follow modern developmental biology. Don’t be dismayed if you find parts of it difficult — it means you’re thinking about new and important stuff!