Princeton President Defends Evolution

On December 1, 2005, Princeton University President Shirley M. Tilghman delivered the 2005 Romanes Lecture at the University of Oxford. Her lecture was entitled “Strange Bedfellows: Science, Politics and Religion”, and addressed both evolution and intelligent design. You can read the full lecture here, but I’ll also provide some excerpts.

“If cosmologists are deciphering the origins of the universe and our solar system in unprecedented ways, biologists are making enormous strides, thanks to the technology that was developed during the Human Genome Project, toward unlocking the origins of life on Earth. Yet here, too, science and politics have found themselves at loggerheads. It is impossible to ignore the increasing assertiveness of elements within American society who have challenged the validity of Darwin’s theory of natural selection and have lobbied for an alternative explanation, which they term “intelligent design,” to be taught in public schools alongside the principles of evolution. This is deeply disturbing, for the theory of natural selection is one of the two pillars, along with Mendel’s laws of inheritance, on which all of modern biology is built. It is virtually impossible to conduct biological research and not be struck by the power of Darwin’s theory of natural selection to shed light on the problem at hand. Time and again in the course of my career, I have encountered a mysterious finding that was explained by viewing it through the lens of evolutionary biology. The power of the theory of natural selection to illuminate natural phenomena, as well as its remarkable resilience to experimental challenge over almost 150 years, has led to its overwhelming acceptance by the scientific community.”

“Today, however, under the banner of “intelligent design,” Christian fundamentalists in the United States have launched a well-publicized assault on the theory of evolution, suggesting that the complexity and diversity of nature is not the product of random mutation and natural selection but rather of supernatural intent. Although exponents of intelligent design have been at pains to distance themselves from overtly religious interpretations of the universe, the intellectual roots of intelligent design can be traced to creationism, which holds that the natural world, including human beings in their present form, is the handiwork of a divine designer — namely, God. Biblical creationists contend that the world was created in accordance with the Book of Genesis — in six short days — while the followers of intelligent design eschew this literalism. They say that their goal is to detect empirically whether the “apparent design” in nature is genuine design, in other words, the product of an intelligent cause. They reject out of hand one of the central tenets of natural selection, namely, that biological change arises solely from selection upon random mutations over long periods of time. For those of you who are not conversant with the literature of intelligent design, the argument usually begins with Darwin himself, who said “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.” From there, advocates such as Michael Behe, a professor of physical chemistry at Lehigh University, declare that “natural selection can only choose among systems that are already working, so the existence in nature of irreducibly complex biological systems poses a powerful challenge to Darwinian theory. We frequently observe such systems in cell organelles, in which the removal of one element would cause the whole system to cease functioning.”

“What is wrong with this view? To begin with, it reflects a fundamental misunderstanding of how evolution works. Nature is the ultimate tinkerer, constantly co-opting one molecule or process for another purpose. This is spurred on by frequent duplications in the genome, which occur at random. Mutations can accumulate in the extra copy without disrupting the pre-existing function, and those that are beneficial have the potential to become fixed in the population. In other instances, entirely new functions evolve for existing proteins. My favorite example is lactate dehydrogenase, which functions as a metabolic enzyme in the liver and kidney in one context, and as one of the proteins that makes up the transparent lens of the eye in another. In the first cellular setting, the protein has a catalytic function; in the second, a structural one.”

“A common weapon that is used to advance the “theory” of intelligent design is to posit that evolutionary biology cannot explain everything — that there remains uncertainty in the fossil record and that there is as yet no consensus on the origin or nature of the first self-replicating organisms. This, too, reflects a basic misunderstanding about how science works, for, in fact, all scientific theories, even those that are approaching 150 years of age, are works in progress. Scientists live with uncertainty all the time and are not just reconciled to it but understand that it is an integral part of scientific progress. We know that for every question we answer, there is a new one to be posed. Indeed, the very word, “theory,” is misunderstood by many who take it to mean an “idea” that has no greater or lesser merit than any other idea. The fact that Darwin’s “ideas” on natural selection have stood the test of time through keen experimental challenge does not give his theory special status in their eyes. There are also those who exploit the fact that scientists often disagree over the interpretation of specific findings or the design of experiments to argue that nothing is settled and thus anything is possible. The fact of the matter is that fierce disagreement is the stuff of scientific inquiry, and the constant give-and-take is needed to test the mettle of our ideas and sharpen our thinking. It is not, as many would claim, prima facie evidence for deep fissures in the central tenets of natural selection.”

Now go and read the full speech.