Sean B. Carroll is a professor of genetics at the University of Wisconsin at Madison and the author of Endless Forms Most Beautiful: The New Science of Evo-Devo (W. W. Norton), which Discover chose as one of our top science books of 2005. In this interview he talks to senior editor Josie Glausiusz about his new book, The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution (W. W. Norton, $25.95).
Why did you write The Making of the Fittest?
Because there has been a flood of wonderful and, I think, profound discoveries in just the last few years that were made by studying the DNA record of evolution. Very little of what is in the book has been shared with the reading public, and most of it is not in textbooks either, but will be.
It is not just the quantity of discoveries that merits attention, it is the quality. Changes in species traits occur through changes in DNA, but until recently, we had very few examples that pinpointed those changes responsible for adaptations. Now we have many examples, and some broader trends emerge—such as the repetition of evolution in exquisite detail, in different species, at different times, in the origin of similar traits.
Why do we need yet another book about evolution?
Evolutionary science is a rich subject that is expanding rapidly. I think the advances explained in this book actually make the process of evolution easier to understand. And, in light of the furor still raging over the teaching of evolution, the book presents a lot of new evidence about how evolution works at the most fundamental level.
Who is your target audience? Who, in your opinion, should read this book?
Anyone with an interest in natural history and the amazing diversity of life. The book looks at fish that live in subfreezing waters, ruminating monkeys, ridiculously poisonous newts, birds that see in the ultraviolet, mice that live on lava flows, cave fish, coelacanths, bush babies, humans, and some other marvels of evolution. There is plenty of new material here for teachers, students, doctors, and scientists of many stripes.
Why did you focus on DNA as a font of evidence for evolution?
To borrow from Willie Sutton, "because that's where the money is." It is the ultimate forensic record of evolution and can tell us so much about both current species and extinct ancestors. It documents the process of natural selection and the relationships throughout the tree of life. I don't think that this power is well appreciated. I also think that folks are interested in DNA. Witness the current popularity of forensics and the confidence that judges and juries are placing on DNA evidence. Same science, different questions.
Why do you think many Americans have such a poor understanding of evolution? Why is there so much opposition to a theory that is amply backed by more than 100 years of research?
That is a good question, and there are many reasons. They are all cultural and not scientific for, as you say, the science has been accepted for more than 100 years and only grows stronger. In the next-to-last chapter in the book, I try to explain both why and how evolution is opposed, first by drawing on examples where solid science was opposed by other groups (DNA as the basis of heredity in the USSR and vaccination by chiropractors). The motivation and tactics of evolution denial are similar to these other situations, which also appear astounding in light of the evidence.
You have strong words for the intelligent design folks, for example, describing one claim by their advocate Michael Behe (that an intelligent designer "made the first cell, already containing all of the irreducibly complex biochemical systems") as "utter nonsense." Do you regard the ID movement as a threat to science? If so, why?
I thought I was being kind. Intelligent design is a creation myth, not science. Do not take my word for it; read the opinion issued in the 2005 Kitzmiller et al. vs. Dover School Board case, which held that "intelligent design is not science and 'cannot uncouple itself from its creationist, and thus religious, antecedents.' " The idea of complex biochemical systems lying dormant until their utilization in later species is absolutely inconsistent with and impossible in light of what we know about genetics and mutation.
ID is a threat to scientific literacy. It is an attempt to wrap a religious idea in the skin of scientific credibility. Many public officials and the media have not done well in piercing this skin. But the courts have now spoken. Given that it has been deemed the progeny of creation science and its teaching is unconstitutional in the public schools, I think the skin is peeling.
Would you publicly debate an intelligent design advocate?
No. And I don't think astronomers should debate astrologers nor surgeons debate faith healers. The ID proponents have succeeded in gaining enormous attention for a notion that the scientific community and the courts have found lacking any scientific substance. ID is an outgrowth of a desire to undermine evolutionary science, which is perceived to be a threat to their religious worldview.
What has been overlooked in the whole furor is that many denominations fully support the science and teaching of evolution. They have reconciled their faith and theology with modern science. That is a far more interesting area of discourse than the tired, empty arguments of evolution denial.
In the introduction to your book, you describe "the bloodless fish of Bouvet Island," icefish so well adapted to the cold oxygen-rich waters of the South Atlantic that they have lost the power to make hemoglobin. You also predict that if climate change warms the water, the icefish will most likely go extinct. Can we prevent this catastrophe?
The icefish vividly illustrates how the fittest is a conditional and precarious condition. Many organisms are adapted to fairly narrow habitats and conditions and do not do well when those conditions are perturbed or they are removed, especially over a short time span, geologically speaking. However, I have only provided an explanation of why species are at risk. The prevention of extinctions is a global issue that seems to be confounded by the familiar forces of doubt and self-interest.
How does your own work increase our understanding of evolution?
My laboratory has focused on the evolution of animal form. Our most significant discoveries have revealed the importance of regulatory DNA in the evolution of complexity and diversity.
What's your next project?
One of the most rewarding aspects of writing for a general audience has been the response of the biology teaching community. I think there is an urgent need to get new, illuminating material into the hands of teachers and their students. I am working on some new paths to do that.