But it's "JUST a THEORY"
Version 1.0
Copyright 1999 by Ken Harding
[last update August 24, 1999]


This is such a common complaint about evolution that it deserves a page of it's own.  This comment is born out of misuse of the word theory.  By uttering statements like: "But it's only a theory; it's not a scientific law," or "It's a theory, not a fact," people reveal that they don't really know the meanings of the words they are using, but instead are merely parroting the talking points of creationist propagandists.

Theory does not mean guess, or hunch, or hypothesis.  A theory does not change into a scientific law with the accumulation of new or better evidence.  A theory will always be a theory, a law will always be a law.  A theory will never become a law, and a law never was a theory.

The following definitions, based on information from the National Academy of Sciences, should help anyone understand why evolution is not "just a theory."



For example, there is the phenomenon of gravity, which you can feel. It is a fact that you can feel it, and that bodies caught in a gravitational field will fall towards the center.  Then there is the theory of gravity, which explains the phenomenon of gravity, based on observation, physical evidence and experiment. Albert Einstein's General Theory of Relativity replaced the less accurate gravity theory of Sir Isaac Newton, which was the first complete mathematical theory formulated which described a fundamental force.

There is the modern theory of evolution, neo-darwinism. It is a synthesis of many scientific fields (biology, population genetics, paleontology, embryology, geology, zoology, microbiology, botany, and more). It replaces darwinism, which replaced lamarckism, which replaced the hypotheses of Erasmus Darwin (Charles' grandfather), which expanded the ideas of Georges de Buffon, which in turn expanded upon the classification of Karl von Linne.  (see also:  Darwin's Precursors and Influences)

So there is the theory of evolution.  Then there is the FACT of evolution.  Species change-- there is variation within one kind of animal. There is a predictable range of genetic variation in a species, as well as an expected rate of random mutations. Creationists readily admit that a "kind" (an ambiguous, non-scientific term) can develop into different species (i.e. a dog "kind" can evolve into wolves, coyotes, foxes, and all types of domestic dogs) but they insist that it must stop there.  They never give any reason for this fabricated limitation-- they just deny that it can happen.  They just can't accept macroevolution, because it contradicts the "truth" of their dogma. But in reality, there is no limit to the degree that a species can change. Given enough time, a fish-like species can evolve into a amphibian-like species, an amphibian-like species can evolve into a reptilian-like species, a reptilian-like species can evolve into a mammalian-like species, and an ape-like species can evolve into the modern human species.

The process (simply stated) involves the genetic potential of many different types of individuals within a species, the birth of a great many individual organisms, and the deaths of those individuals whose characteristics are not as well suited to the total environment as other individuals of the same species. The deaths of these less well suited individuals allows for the increased reproduction of the better suited ones, which initiates a shift in the appearance and function of the species. Without limitation.  There is more genetic stuff to it than that, but that is basically how it works.

Yes, evolution is a fact, as real as gravity. The fact that all species alive today have descended from a common ancestor can be denied, but not refuted. We know it happens because we can observe it directly in short-lived species, and for longer lived species there is genetic and fossil evidence that is unambiguous. There is no other scientific explanation for the diversity of living species.  Evolution is a very well established scientific concept with a massive amount of physical evidence for support.  It is not a guess.  Evolution is the basis of modern biology, and  universities and laboratories across the world are engaged in research that explores evolution.

You don't have to 'believe' in evolution. You can trust that the thousands of scientists who study this phenomenon aren't morons, or Satanists. You can accept the general idea that life propagates with modifications, and those modifications can lead to improved survival, and that as those modifications are passed over time, many modifications can lead to a species that looks very different from its predecessor. Is that so hard to accept?

I have no faith at all in evolution. (I also have no faith in algebra, chemistry or astronomy). Evolution either stands or falls by the strength of the evidence used to substantiate it. Evolutionary biology relies on factual data, physical evidence, molecular experimentation, and it goes hand in hand with geology.

Some people can say "Well, scientists weren't there... they don't know what happened.  It's still faith."   But that is mere blind objectionism, like an ostrich hiding its head in the sand.  There are real reasons behind the science of reconstructing the past.  My favorite analogy is forensic science. A man can murder someone (with no witnesses), and scientists can reconstruct the scene with such accuracy as to pinpoint the guilty person-- with such accuracy as to cause that man to receive the death penalty.  For example, most Americans are convinced of O.J. Simpson's guilt... even though no one was there to see him do it.   The situation with evolution is much the same-- reconstructing the past through examination of the evidence.  It's true that not every theory withstands the test of time and goes on to be considered a fact by nearly all of the scientific community, but evolution is one that has.

See also:  Evolution is a Fact and a Theory

This is the statement from the National Academy of Science:

Is Evolution a fact or a theory?
The theory of evolution explains how life on earth has changed. In scientific terms, "theory" does not mean "guess" or "hunch" as it does in everyday usage. Scientific theories are explanations of natural phenomena built up logically from testable observations and hypotheses. Biological evolution is the best scientific explanation we have for the enormous range of observations about the living world.  Scientists most often use the word "fact" to describe an observation. But scientists can also use fact to mean something that has been tested or observed so many times that there is no longer a compelling reason to keep testing or looking for examples. The occurrence of evolution in this sense is a fact.  Scientists no longer question whether descent with modification occurred because the evidence supporting the idea is so strong.

Why isn't evolution called a law?
Laws are generalizations that describe phenomena, whereas theories explain phenomena. For example, the laws of thermodynamics describe what will happen under certain circumstances; thermodynamics theories explain why these events occur. Laws, like facts and theories, can change with better data. But theories do not develop into laws with the accumulation of evidence. Rather, theories are the goal of science.

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