Volume 12, Number 2

The Status of Evolution as a Scientific Theory


In the National Academy of Sciences' booklet Science and Creationism, we are told that the "theory of evolution has withstood the tests of science many, many times"; that "the debate [among scientists] centers only on the finer details of how it took place," not whether it took place; that evolution is to be classed among theories which are "supported by evidence, and which survive the rigorous testing of the scientific method," like the "germ theory of disease" and the "theory of gravity," whereas creation is to be classed among theories "that have long been invalidated by observations and experiments." (Committee on Science and Creationism, 1984, p. 6. Emphasis in original.) Similar comments occurred in the California Science Framework Draft:

Evolution is the central organizing theory of biology, and has fundamental importance in other sciences as well. It is no more controversial in scientific circles than gravity or electricity is...And, regardless of whether the changes in plants and animals are gradual or sporadic, the facts remain that plants and animals have evolved over time. There is no scientific dispute that evolution has occurred and continues to occur; this is why evolution is regarded as a scientific fact. (State of California, 1989, pp. 14-15.)

Is evolution fact and creation merely faith? Or is evolution faith and creation fact? Is one true and the other false, are both true or, for that matter, both false? This controversy--whether in the media, classroom or courtroom--has often generated more heat than light. Here we hope to shine a little light on one question relevant to the dispute: what is the epistemological status of evolution? How certain is it as a theory? In what sense can one say that evolution is a fact?

Some Definitions



The adjective scientific calls for a brief comment. Without getting into boundary disputes between the disciplines of science and history, or arguments among philosophers over various definitions of the scientific method, there appears to be one rather important ambiguity in the definition of "science" or "scientific." Sometimes science is understood to mean 1) an attempt to explain how things actually are. At other times, the term is used to mean 2) explanation without recourse to the supernatural. These definitions are only equivalent if in fact there has never been any supernatural intervention in the history of our universe. The claim that such alternative definitions are interchangeable is itself a distinct philosophical worldview--naturalism, secular humanism, or something of the sort. To switch back and forth between these definitions without comment has certainly tended to confuse the creation/evolution controversy, and seems to have been a significant factor in recent court decisions on the subject.

What is meant by the term evolution? Thomson (1982) has distinguished three meanings: 1) biological change over time; 2) descent through common ancestry; and 3) the Darwinian mechanism of mutation and natural selection. A fourth definition is also commonly used today, 4) an extension of the term beyond biology to include the origin and development of the universe, galaxy, sun and earth. Finally, the word can also be used in an everyday sense as 5) a general synonym for change or development, as in "the evolution of the computer."

We can exclude (5) from consideration, as hardly anyone but the ancient Greek philosopher Parmenides would be against evolution in this sense--certainly not creationists. At least, this is not what the present controversy is all about. We will also exclude (4) from the scope of this particular paper. Note, however, that using the label "evolution" not only for biological origins but also for cosmological origins can easily be misleading. While it gives us the feeling that a "grand unification" has been achieved, it may lead us to overlook problems in one of these theories by encouraging us to think that evidence for one is really evidence for the other.


Evolution as Biological Change

Since it is obvious that children are not identical to their parents, some biological change is as certain as the reliability of our senses. In this sense, evolution (as biological change) is a fact, at least as certain as that the earth is round. This, however--and the equally obvious fact that individuals change as they grow older--is not really the point at issue in the creation/evolution controversy, since all creationists agree that this is so. This is at most an argument from analogy, as all agree that the mechanisms of growth and aging are different from that of Darwinism. Such considerations ought not to be brought into the debate if one is concerned to clarify what is at stake rather than muddy the waters.


Creationists of the young-earth variety must deny that the geologic strata provide a sequential record of the history of life in order to avoid this conclusion. This is no doubt the reason for the popularity of flood geology in such circles. With this mechanism, young-earth creationists claim that nearly all the fossils in the geologic column were laid down at the flood and lived simultaneously on the earth up to that time. There are, however, severe scientific problems with flood geology, as old-earth creationists have regularly pointed out (e.g. Young, 1977, 1982; Wonderly, 1978, 1987).

We must admit that inferences about the past from present day observations are epistemologically of somewhat lower certainty than observations of change in oneself or ones' parents based on personal memory and photographs. Nevertheless, evolution, in sense (1), that large biological changes have taken place in geologic history, is as certain as that the earth and its geologic strata are millions to billions of years old (rather than thousands) and that the strata provide a reliable history of this time-span. Compared with other scientific theories, this would make evolution (1)--large-scale biological change--a "historical" theory like big-bang cosmology, continental drift or climatic change caused by long-term variation in the earth's orbit. This is in contrast to a "laboratory" theory like electromagnetism, the germ theory of disease, or gravity. Though we certainly don't understand everything there is to know about electromagnetism or gravity, the theories themselves refer to currently-occurring, short-term, repeatable phenomena. Such long-term actions of (say) gravity as operate in the expansion of the universe or the formation of stars are typically considered as components of particular historical theories in cosmology or astronomy, rather than under the theory of gravity per se, so long as gravity itself is not viewed as changing character with time.

Evolution as Descent Through Common Ancestry

Accepting the geologic record as a history of life on earth covering more than a billion years, it is easy to see how scientists can feel that descent with modification (evolution in sense (2)) has occurred. Yet a sequence of similar fossils is not the same thing as a genealogy, and the descent of one animal from a similar one living earlier is still an inference, particularly when the difference between the two is much greater than differences between known ancestor-descendant pairs today. It might be that the apparent successor was actually independently created instead, or that it was brought to earth by extra-terrestrials. And even within the category of descent, it might be true that a successor was created from its predecessor by a coordinated set of mutations that could only be considered designed.



It remains true, as every paleontologist knows, that most new species, genera, and families, and nearly all categories above the level of families appear in the record suddenly and are not led up to by known, gradual, completely continuous transitional sequences. (Simpson, 1953, p. 360. Emphasis in original.)

Darwin felt the force of this argument, which was raised against evolution from the first, but he hoped that such gaps would be filled-in as the fossil record was investigated. More than a century of further research, however, has not borne him out. Nor do the gaps appear to be a fluke due to the imperfection of the fossil record:

It is a fact that discontinuities are almost always and systematically present at the origin of really high categories, and, like any other systematic feature of the record, this requires explanation. (Simpson, 1953, p. 361.)

The explanation provided in the 1930s was the neo-Darwinian modification, which put nearly all evolution in small isolated populations of plants or animals that were evolving rapidly, rather than in the slow drift of large populations. This has a certain plausibility for single mutations, which might establish themselves in a small population by statistical fluctuations (~N[-1/2]); but changes requiring several coordinated mutations need large populations to increase the chances (~N) of getting the needed additional mutations. Apart from a mechanism that predicts enormously faster transformation in smaller populations, this is purely an ad hoc proposal or even special pleading. We can paraphrase the argument that Sagan uses to dismiss UFO sightings: "there are no cases that are simultaneously very reliable" (a nice sequence of transitional fossils) "and very exotic (a transition between upper levels of the biological classification scheme). (Sagan, 1975, p. 199.)





Evolution as the Darwinian Mechanism


But evolution (3) runs into serious problems on the macroevolutionary level. Attempts to simulate the Darwinian mechanism by computer have not produced the desired result of generating new organizational structures. Instead random changes in the computer language simulating the DNA sequence have produced degradation rather than increasing order (Moorehead and Kaplan, 1967).


Comparing Evolution with other Scientific Theories




Taking evolution to mean the Darwinian mechanism of mutation and natural selection, nearly everyone agrees that this occurs on the microevolutionary level. The question is, does this mechanism give evidence that it is adequate to explain the much larger diversity that we see at the upper levels of the biological classification scheme? Currently it does not, suggesting that something rather different is at work on these levels. In this sense, it appears that evolution is a historical theory without an adequate known mechanism, more like Everett's (1953) many-worlds theory of quantum mechanics 5 or Norman's and Setterfield's (1987) theory of a changing speed of light than like continental drift or climate change due to long-term variation in the earth's orbit.

In closing, it is worth noting that proving the theory of evolution, even in most of its macroevolutionary forms, would not disprove the existence of a Creator. For the demonstration of a "naturalistic" mechanism does not, in itself, exclude a Designer who uses that mechanism as a tool to achieve certain purposes. Consequently, it is entirely possible for a scientist to investigate "how God may have done it," without compromising either his religious convictions or his scientific credibility.6


Committee on Science and Creationism, Science and Creationism: A View from the National Academy of Science (Washington, DC: National Academy Press, 1984), 6; emphasis in original.

Denton, M. Evolution: A Theory in Crisis (Bethesda, MD: Adler and Adler, 1986), 274-307.

Everett, H. "'Relative State' Formulation of Quantum Mechanics," Reviews of Modern Physics 29 (1953): 454-62;

Moorehead, P.S. & Kaplan, M.M., eds. Mathematical Challenges to the Neo-Darwinian Interpretation of Evolution (Philadelphia: Wistar Institute Press, 1967).

Norman, T. & Setterfield, B. The Atomic Constants, Light, and Time (Menlo Park, CA: Stanford Research Institute International, 1987).

Sagan, C. The Cosmic Connection (New York: Dell, 1975), 199.

Simpson, G.G. The Major Features of Evolution (New York: Columbia University Press, 1953).


Thomson, K.S. "The Meaning of Evolution," American Scientist 70 (Sept-Oct 82): 529-31.

Wonderly, D.E. God's Time Records in Ancient Sediments (Flint, MI: Crystal Press, 1978).

Wonderly, D.E. Neglect of Geologic Data: Sedimentary Strata Compared with Young-Earth Creationist Writings (Hatfield, PA: IBRI, 1987).

Young, D.A. Creation and the Flood (Grand Rapids, MI: Baker Book House, 1977).

Young, D.A. Christianity and the Age of the Earth (Grand Rapids, MI: Zondervan, 1982)


  2. John A. Bloom: BA (physics, chemistry), Grinnell College; MS (physics), PhD (biophysics), Cornell University; MA (Old Testament), MDiv, Biblical Theological Seminary; MA, PhD candidate (ancient near eastern studies), Dropsie University; instructor in physics. Ursinus College; computer consultant, Annenberg Research Center.
  4. John C. Studenroth: BS (botany), MS (botany & plant pathology), University of Maine; PhD (plant pathology), Cornell University; MA (Old Testament), MDiv, Biblical Theological Seminary; PhD candidate (ancient near eastern studies), Dropsie University; instructor in biology, Pinebrook Junior College.
  6. Our thanks to John Wiester for valuable input.

Copyright © 1995 Robert C. Newman, John A. Bloom, Perry G. Phillips, and John C. Studenroth. All rights reserved. International copyright secured.
File Date: 9.2.95