Book Smart

Endless Forms Most Beautiful: The New Science of Evo Devo (W.W. Norton & Co., 2005)
Sean Carroll, professor of genetics and molecular biology

For 15 years, I have had the great fortune to sit at the knee of biologist Sean Carroll and be tutored in the molecular subtleties of animal form. Within any animal, it is nature’s fine print, DNA, that determines form and function. This simple fact is known, of course, by anyone with even a passing knowledge of biology. Everything from the decoration of a fruit fly’s butt to the flukes of a blue whale can be read in long sequences of amino acids.

But how do animal forms come to be to begin with? How are genes used to paint the patterns of a butterfly’s wing or the stripes of a zebra? How does nature direct this genetic machinery? How does it change over time? And how does all of this fit into the big picture of evolution and natural selection?

Over the past decade and a half, in one high-profile paper after another, Carroll and his labmates have helped answer many of these questions and more. They have dug deep into the genomes of fruit flies, yeasts, butterflies and obscure microorganisms called choanoflagellates not only to plumb the mysteries of modern animal form, but to look back hundreds of millions of years to try to discern the advent of the genetic tool kits at work in all of us today.

Now, Carroll has taken on a task perhaps far more daunting than front-line molecular biology. In his new book, “Endless Forms Most Beautiful,” Carroll is attempting to make the intricacies — and deep beauty — of evolutionary developmental biology plain to the world. Evo devo is peeling back the mystery of how, at the deepest level, animals are made. Perhaps its most astonishing contribution to our understanding of how animals develop is that a relatively small number of genes, many of which appear to be ancient, are responsible for forging critical organs and appendages in all animals. The same gene that governs how you grow an arm is used by a bird to grow a wing and a fruit fly to grow a leg. The big differences in form between a primate’s arm and an insect’s leg boil down to how the genetic tool kit is used, according to Carroll.

As a science writer, the joy of a trip to Bock Labs to interview Carroll was underwritten not only by the knowledge that there always was a good story waiting, but that the tale was going to be told well, in artful language and richly illustrated with analogy and metaphor. In “Endless Forms Most Beautiful,” Carroll demonstrates his knack for making evo devo accessible to the rest of us. In 11 chapters, Carroll walks the reader through the basics of animal architecture and the role genes play in transforming a simple egg to a complex animal. Along the way, we learn about the genetic tool kit. In a fruit fly, there are perhaps several hundred genes (out of 13,676 in the insect’s genome) that govern the patterning and construction of the animal. Among those, there are a dozen or so well-known master genes, the genes that make eyes, limbs and hearts.

Carroll’s infectious wonder extends to the genetic underpinnings of zebras and butterflies and jaguars and pocket mice and to humans. The power of modern biology, its ability to extract the closely held secrets of nature, of how we and the other animals came to be, is revealed for all of us to understand in this readable, but hardly science-lite text.

And it’s a good thing, too. In concluding his book, Carroll notes the abysmal state of scientific understanding by Americans. In particular, he laments the fact that evolution, a central thesis of biology, is losing ground in the culture wars. Evo devo, and other biological pursuits, have given us a mountain of evidence that Darwin was right. Carroll’s “Endless Forms Most Beautiful,” which takes its name from Darwin’s most famous tract, provides us with forceful, elegant access to that evidence.

— Terry Devitt