From: lamoran@gpu.utcs.utoronto.ca (L.A. Moran)
Subject: Evolution is a fact.
Organization: UTCS Public Access
Date: Thu, 3 Sep 1992 13:31:49 GMT


                    EVOLUTION AS A FACT AND A THEORY

When non-biologists talk about evolution they often confuse two different
aspects of the definition. On the one hand there is the question of whether
or not modern organisms have evolved from older ancestral organisms or 
whether modern species are continuing to change over time. On the other
hand there are questions about the mechanism of change... how did evolution
occur? Biologists consider evolution to be a FACT. It can be demonstrated
today and the evidence for it's occurrence in the past is overwhelming. 
But there are several THEORIES of the MECHANISM of evolution.

Stephan J. Gould has put this as well as anyone else,

     "In the American vernacular, "theory" often means "imperfect fact"
      - part of a hierarchy of confidence running downhill from fact to
      theory to hypothesis to guess. Thus the power of the creationist 
      argument: evolution is "only" a theory and intense debate now rages 
      about many aspects of the theory. If evolution is worse than a fact,
      and scientists can't even make up their minds about the theory, then
      what confidence can we have in it? Indeed, President Reagan echoed
      this argument before an evangelical group in Dallas when he said 
      (in what I devoutly hope was campaign rhetoric): 'Well, it is a 
      theory. It is a scientific theory only, and it has in recent years
      been challenged in the world of science - that is, not believed in
      the scientific community to be as infallible as it once was.'

      Well evolution is a theory. It is also a fact. And facts and theories
      are different things, not rungs in a hierarchy of increasing certainty.
      Facts are the world's data. Theories are structures of ideas that
      explain and interpret facts. Facts don't go away when scientists
      debate rival theories to explain them. Einstein's theory of gravitation
      replaced Newton's in this century, but apples didn't suspend themselves 
      in midair, pending the outcome. And humans evolved from ape-like 
      ancestors whether they did so by Darwin's proposed mechanism or by 
      some other yet to be discovered.

      Moreover, 'fact' doesn't mean 'absolute certainty'; there ain't no
      such animal in an exciting and complex world. The final proofs of
      logic and mathematics flow deductively from stated premises and
      achieve certainty only because they are NOT about the empirical
      world. Evolutionists make no claim for perpetual truth, though
      creationists often do (and then attack us falsely for a style of
      argument that they themselves favor). In science 'fact' can only
      mean 'confirmed to such a degree that it would be perverse to
      withhold provisional consent'. I suppose that apples might start
      to rise tomorrow, but the possibility does not merit equal time in
      physics classrooms.

      Evolutionists have been very clear about this distinction of fact
      and theory from the very beginning, if only because we have always
      acknowledged how far we are from completely understanding the
      mechanisms (theory) by which evolution (fact) occurred. Darwin
      continually emphasized the difference between his two great and
      separate accomplishments: establishing the fact of evolution, and
      proposing a theory - natural selection - to explain the mechanism
      of evolution."
  
      Stephen J. Gould "Evolution as Fact and Theory"; Discover, May 1981

Gould is stating the prevailing view of the scientific community. In other 
words, the experts on evolution consider it to be a FACT. This concept is also
explained in introductory biology books that are used in colleges and
universities (and in some of the better high schools). For example, in some
of the best such textbooks we find,

     "Today, nearly all biologists acknowledge that evolution is a fact.
      The term THEORY is no longer appropriate except when referring to
      the various models that attempt to explain HOW life evolves...
      it is important to understand that the current questions about
      how life evolves in no way implies any disagreement over the fact
      of evolution."

      Neil A. Campbell, BIOLOGY 2nd ed., 1990, Benjamin/Cummings, p.434

     "Since Darwin's time, massive additional evidence has accumulated
      supporting the fact of evolution - that all living organisms present
      on earth today have arisen from earlier forms in the course of
      earth's long history. Indeed, all of modern biology is an affirmation
      of this relatedness of the many species of living things and of
      their gradual divergence from one another over the course of time.
      Since the publication of The Origin of Species, the important 
      question, scientifically speaking, about evollution has not been
      whether it has taken place. That is no longer an issue among the 
      vast majority of modern biologists. Today, the central and still
      fascinating questions for biologists concern the mechanisms by
      which evolution occurs."

      Helena Curtis and N. Sue Barnes, BIOLOGY 5th ed. 1989,
      Worth Publishers, p.972

One of the best introductory books on evolution (as opposed to introductory
biology) is that by Douglas J. Futuyma, and he makes the following comment,

     "A few words need to be said about the 'theory of evolution', which
      most people take to mean the proposition that organisms have evolved
      from common ancestors. In everyday speech, 'theory' often means a
      hypothesis or even a mere speculation. But in science, 'theory'
      means 'a statement of what are held to be the general laws, principles,
      or causes of something known or observed", as the Oxford English
      Dictionary defines it. The theory of evolution is a body of 
      interconnected statements about natural selection and the other 
      processes that are thought to cause evolution, just as the atomic
      theory of chemistry and the Newtonian theory of mechanics are bodies
      of statements that describe causes of chemical and physical phenomena.
      In constrast, the statement that organisms have descended with 
      modifications from common ancestors - the historical reality of
      evolution - is not a theory. It is a fact, as fully as the fact of
      the earth's revolution about the sun. Like the heliocentric solar
      system, evolution began as a hypothesis, and achieved "facthood" as
      the evidence in its favor became so strong that no knowledgeable
      and unbiased person could deny its reality. No biologist today
      would think of submitting a paper entitled "New evidence for 
      evolution"; it simply has not been an issue for a century."

                                  Douglas J. Futuyma, op. cit., p.15

There are readers of these newsgroups who reject evolution for religious 
reasons. In general these readers oppose both the FACT of evolution and 
THEORIES of mechanisms although some creationists have come to realize that 
there is a difference between the two concepts. That's why we see some leading
creationists admitting to the fact of "microevolution" - they know that
evolution can be demonstrated. What I find so bizarre is that there are some 
readers, who are not creationists, but still claim that evolution is "only" 
a theory which can't be proven. This group needs to distinguish between the
fact that evolution occurs and the theory of the mechanism of evolution.

We also need to distinguish between facts that are easy to demonstrate and
those that are more circumstantial. Examples of evolution that are readily
apparent include the fact that modern populations are evolving and the fact
that two closely related species share a common ancestor. The evidence that
Homo sapiens and chimpanzees share a recent common ancestor falls into this
catagory. There is so much evidence in support of this aspect of primate
evolution that it qualifies as a fact by any common definition of the word
"fact".

Other examples of evolution are less secure. For example, the relationships
between various protozoa are not understood. The statement that all organisms
have descended from a single common ancestor is strongly supported by the 
available evidence, and there is no opposing evidence. However, it is not 
appropriate to call this a "fact" since there are reasonable alternatives.

It is also important to distinguish between evolution and the origin of life.
Evolution, per se, does not cover the origin of life. Those who reject
evolution because it doesn't explain the origin are life are fighting a straw
man. 

April 5, 1992

Laurence A. Moran (Larry)
Dept. of Biochemistry               lamoran@gpu.utcs.utoronto.ca
Medical Sciences Blgd.                    (416) 978-2704
University of Toronto               FAX   (416) 978-8548
Toronto M5S 1A8, CANADA
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