You have no doubt seen the "Darwin Fish" and recognized it as a fun parody of the ubiquitous "Christian Fish." The second proclaims, "I believe in Christ and his gospel." Does this imply that the former means, "I believe in Darwin and his Origin of Species?"

As a former professor of zoology and high school teacher of biology, I certainly use evolution as an explanation for the origin of life on earth and the development of humankind. I don't believe it, but I use it. Do these two clauses seem to be in conflict with each other? In the world of science, they aren't.

It is a simple truth that science, when employed beyond its surface features, does not produce believers of its practitioners. Do scientists really believe in atoms? Do they believe that the California fault system is a function of plate tectonics? Stated as plainly and simply as is possible, the answer is, "NO!"

Take the case of the atom. In the fifth century BCE, the Greek philosopher Democritus stated, on the basis of logic, that he believed that all matter could be subdivided into smaller and smaller parts until it reached some final indivisible part; this part he termed the atom. Democritus indeed had a philosophically based belief in atoms. Later, others started to demonstrate through measurements in chemical reactions some real physical substantiation for the existence of such structures. More and more information began accumulating, allowing science to explain one important part of the universe, the chemical behavior of matter.

Scientists' explanation of accruing physical evidence has developed into what is known as the Theory of Atomic Structure. The theory is not a belief system, it is a tool. Its component propositions are not taken on faith, like religious tenets. Atomic theory is more analogous to a hammer than a religion. That is, atomic theory is a tool that is employed to do a task, such as explain how chemicals interact with each other. In my teaching lifetime, I have had to relearn the answer to "what is an atom like?" several times. As more evidence is gained, the conception of atomic structure improves and major changes are made to the theory. So it is with all scientific theories.

Idea One: Scientific theories are tools, not belief systems. It is incorrect (and misleading to others less well informed) to state something like "I believe in the Theory of Evolution."

Idea Two: Science progresses by tossing out or modifying the old. One must be prepared to accept new tools (theories) the moment new evidence overwhelms the old.

Parts of the Theory of Evolution Through Natural Selection consist of broad statements that are so clearly documented in evidence that there is no disagreement within the scientific community as to their validity. More than 99% of all biologists agree with this portion of the theory, leading us to call these "scientific facts."

There is no doubt that evolution occurs. The theoretical construct of how is currently ascribed to natural selection. There have been other theories to explain evolution. For example, in the 19th century Lamarck proposed evolution through use and disuse of organs called the Theory of Acquired Characteristics. At the moment there are no strong theories competing with natural selection, although there are alternate, competing versions of natural selection-for example, punctuated evolution versus steady stream evolution. (There is a political movement to foster a competing "theory of scientific creationism," but this is a religious conception masquerading as science.) Therefore it is a verity that biologists of all sorts all over the world use the Theory of Evolution Through Natural Selection as a tool to explain the inter-relationships of life on Earth.

Idea Three: Evolution, or change of life through time, is a scientific fact.

Idea Four: The predominant theory of how evolution works is the Theory of Natural Selection.

Idea Five: The current Theory of Evolution through Natural Selection is a tool that will be discarded the moment science comes up with a better theory.

Back to that Darwin Fish on our cars. It is (or should be) a nifty symbol that there are people who prefer scientific explanations to religious ones. It may open up social opportunities to enlighten others on how scientific explanations differ from those that must be taken on faith.

--Paul Geisert