Intelligent Design as an Alternative Explanation for the Existence of Biomolecular Machines

Intelligent Design as an Alternative Explanation for the Existence of Biomolecular Machines Michael J. Behe Preliminary Issues Before I explain why I disagree with the common scientific understanding of how life developed, there are several preliminary issues to address. First is the problem of equivocation. The word "evolution" can be used to stand for different, partially overlapping concepts: change over time; common descent; and Darwinian natural selection.1 Change over time (where, for example, a species existed in the past but no longer exists today) is not controversial. Common descent (that all species alive today are related by descent from a common ancestor) is more controversial but, in an important way, is intellectually trivial. Common descent is an explanation for the similarities among species. Science has shown many similarities between organisms, especially at the molecular level. Explaining similarities, however , is the easy part. One simply has to say that preexisting features remained the same. Explaining the many profound differences between organisms—and where the features came from in the first place—is the hard part. Darwin tried to explain the hard part. He proposed the theory of natural selection to account for the differences between organisms. Briefly, Darwin saw that there was variation in all species, and he reasoned that animals whose random variation gave them an edge in the struggle to survive would tend to leave more offspring than others. If the variation were inherited, then the characteristics of the species would change over time. Over great periods, perhaps great changes could occur. In other words, Darwin proposed a mechanism to drive evolutionary change. The more difficult the problem, the less likely that a proposed solution is the final answer. Although it clearly can explain relatively small changes, the sufficiency of Darwin's mechanism to account for larger, more complex changes in organisms remains in question. Mechanism, the focus of this paper, however, is the heart of Michael J. Behe is Professor of Biological Sciences at Lehigh University in Bethlehem, Pennsylvania, and a Fellow in the Discovery Institute Center for the Renewal of Science and Culture in Seattle, Washington. © Rhetoric & Public Affairs Vol. 1, No. 4,1998, pp. 565-570 ISSN 1094-8392 566 Rhetoric & Public Affairs evolution. In the absence of a known mechanism the concept of evolution can stray very far from the popular understanding of that word. The second preliminary issue concerns the level at which we must account for evolution. To explain the workings of a physical system one must understand all of the relevant parts and how they interact to give an observed effect. For example, a child's swing set can be explained in terms of the shape and hardness of nuts, bolts, metal bars, and so on. We do not have to worry about interactions of atoms in the metal components. For a system like a computer, however, we have to know much more than shape and hardness. In its critical processing components, a computer's activity depends on intricate chemical, electrical, and physical properties at the atomic level. In the detail required to explain them and their evolution, biological systems are much more like computers than swing sets. One has to understand organisms down to the molecular level to truly account for their workings. Consider that a prerequisite of Darwinian evolution is mutation. Mutations are molecular events—changes at the level of DNA. Genetic diseases such as cystic fibrosis and sickle cell anemia show us that molecular mistakes can have severe consequences for the whole organism . Clearly, then, any theory of evolution must explain not only fossils, bones, and organs, but ultimately the molecular workings of life. It is my professional judgment that Darwin's theory cannot do so. Let me explain why. The Importance of Being Gradual In the Origin of Species Darwin stated: 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.2 Darwin was emphasizing that his theory required gradualism. Complex adaptations must be built step by tiny step, he thought. The reason for his emphasis on gradualism is that random beneficial changes are rare. Therefore the appearance of...