From: lamoran@gpu.utcs.utoronto.ca (L.A. Moran)
Subject: EVOLUTION IS A FACT
Organization: UTCS Public Access
Date: Sat, 23 Jan 1993 22:22:02 GMT


                    EVOLUTION AS A FACT AND A THEORY
                     version 2.1 (January 22, 1993)

When non-biologists talk about biological 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 the observed changes... how 
did evolution occur? Biologists consider the existence of biological evolution
to be a FACT. It can be demonstrated today and the historical evidence for 
it's occurrence in the past is overwhelming. However, biologists readily admit
that they are less certain of the exact MECHANISM of evolution; 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 is not an idea
that originated with Gould as the following quotations indicate;

     "Let me try to make crystal clear what is established beyond 
      reasonable doubt, and what needs further study, about evolution.
      Evolution as a process that has always gone on in the history of
      the earth can be doubted only by those who are ignorant of the 
      evidence or are resistant to evidence, owing to emotional blocks
      or to plain bigotry. By contrast, the mechanisms that bring 
      evolution about certainly need study and clarification. There are
      no alterantives to evolution as history that can withstand critical
      examination. Yet we are constantly learning new and important facts
      about evolutionary mechanisms."

      Theodosius Dobzhansky "Nothing in Biology Makes Sense Except in the
      Light of Evolution", American Biology Teacher vol.35 (March 1973)
      reprinted in EVOLUTION VERSUS CREATIONISM, J. Peter Zetterberg ed.,
      ORYX Press, Phoenix AZ 1983

                -----------------------------------------------

     "It is time for students of the evolutionary process, especially 
      those who have been misquoted and used by the creationists, to 
      state clearly that evolution is a FACT, not theory, and that what
      is at issue within bology are questions of details of the process
      and the relative importance of different mechanisms of evolution.
      It is a FACT that the earth with liquid water, is more than 3.6
      billion years old. It is a FACT that cellular life has been around 
      for at least half of that period and that organized multicellular
      life is at least 800 million years old. It is a FACT that major 
      life forms now on earth were not at all represented in the past. 
      There were no birds or mammals 250 million years ago. It is a FACT
      that major life forms of the past are no longer living. There used
      to be dinosaurs and Pithecanthropus, and there are none now. It is
      a FACT that all living forms come from previous living forms. 
      Therefore, all present forms of life arose from ancestral forms that
      were different. Birds arose from nonbirds and humans from nonhumans.
      No person who pretends to any understanding of the natural world
      can deny these facts any more than she or he can deny that the 
      earth is round, rotates on its axis, and revolves around the sun.
           The controversies about evolution lie in the realm of the
      relative importance of various forces in molding evolution."

      R. C. Lewontin "Evolution/Creation Debate: A Time for Truth"
      Bioscience 31, 559 (1981) reprinted in EVOLUTION VERSUS CREATIONISM
      op cit.

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 evolution 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 anti-evolutionists have come to realize 
that there is a difference between the two concepts. That is why we see some 
leading anti-evolutionists admitting to the fact of "microevolution" - they 
know that evolution can be demonstrated. These readers will not be convinced
of the "facthood" of (macro)evolution by any logical argument and it is a 
waste of time to make the attempt. The best that we can hope for is that they
understand the argument that they oppose. Even this simple hope is rarely
fulfilled.

There are some readers who are not anti-evolutionist 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".

In other cases the available evidence is less strong. For example, the 
relationships of some of the major phyla are still being worked out. Also,
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 yet appropriate to call this a "fact" since there
are reasonable alternatives.

Finally, there is an epistemological argument against evolution as fact.
Some readers of these newsgroups point out that nothing in science can
ever be "proven" and this includes evolution. According to this argument,
the probability that evolution is the correct explanation of life as we
know it may approach 99.9999...9% but it will never be 100%. Thus evolution
cannot be a fact. This kind of argument might be appropriate in a philosophy
class (it is essentially correct) but it won't do in the real world. A "fact",
as Stephen J. Gould pointed out (see above), means something that is so highly
probable that it would be silly not to accept it. This point has also been
made by others who contest the nit-picking epistemologists.

     "The honest scientist, like the philosopher, will tell you that
      nothing whatever can be or has been proved with fully 100%
      certainty, not even that you or I exist, nor anyone except himself,
      since he might be dreaming the whole thing. Thus there is no sharp 
      line between speculation, hypothesis, theory, principle, and fact,
      but only a difference along a sliding scale, in the degree of
      probability of the idea. When we say a thing is a fact, then, we
      only mean that its probability is an extremely high one: so high
      that we are not bothered by doubt about it and are ready to act 
      accordingly. Now in this use of the term fact, the only proper one,
      evolution is a fact. For the evidence in favor of it is as voluminous,
      diverse, and convincing as in the case of any other well established
      fact of science concerning the existence of things that cannot be
      directly seen, such as atoms, neutrons, or solar gravitation ....
          So enormous, ramifying, and consistant has the evidence for
      evolution become that if anyone could now disprove it, I should
      have my conception of the orderliness of the universe so shaken 
      as to lead me to doubt even my own existence. If you like, then,
      I will grant you that in an absolute sense evolution is not a fact,
      or rather, that it is no more a fact than that you are hearing or
      reading these words."
       
      H. J. Muller, "One Hundred Years Without Darwin Are Enough"
      School Science and Mathematics 59, 304-305. (1959) reprinted
      in EVOLUTION VERSUS CREATIONISM op cit.

In any meaningful sense evolution is a fact but there are various theories
concerning the mechanism of evolution.


Laurence A. Moran (Larry)
Newsgroups: talk.origins