Ridley Chapter 1
History of evolutionary ideas --- Part 1, before Darwin

Evolution is a theory with a bumpy history.  That history brings with it much baggage, in the form of ideas, words, and controversies that continue to shape discussion of evolution today.  So we begin by looking at that history, not just out of respect for the workers that have gone before but because understanding that history can illuminate important current difficulties.

BRIEF OUTLINE (hyperlinks to expanded outline; use "back" button to return)

• Prelude to evolution.
  
  • Age of Discovery
    • Systematics.
    • Fossils.
    • Diversity and Biogeography.
    • "Clockwork Universe".
  • Obstacles to appreciating evolution.
    • Christian theology.
      • "Young Earth".
      • Noah's Flood.
    • Scientific theories and empirical observations.
      • Fixity of species.
      • Scala naturae.
      • Catastrophism.
      • Refutation of spontaneous generation.
      • Vitalism.
• The "new" science of geology.
  • Nicolaus Steno's laws (1669).
    • Law of Superposition.
    • Law of Original Horizontality.
    • Law of Concealed Stratification.
  • James Hutton (1795).
  • William Smith (1815).
  • Georges Cuvier (1813).
  • Charles Lyell .
• Charles Darwin.

• Continued in Chapter 1, part 2 , History of evolutionary ideas after Darwin.

• Readable references.
• Recent items of relevance to this chapter

• Prelude to evolution.
       Sometimes well-established ideas can seem self-evidently true, until we realize how strange they really are and what older concepts and intuitions once stood in the way of their acceptance.  Some old ideas may seem quaint or even silly until we remember how rational they once were when less was known.  Science really does progress.  To properly understand evolution's place in modern science, we need to consider what discoveries were needed to make such a theory necessary, and what older ideas needed to be overthrown.

       Perhaps even more importantly, many of the original problems in evolutionary biology remain unresolved, and the roots of many modern contorversies extend back many decades.

  • In the Age of Discovery, new information set the stage for Darwin.
    • Systematics.  Linneaus Systemae Naturae (1758) classified organisms into nested sets of taxa.  This was a pattern in need of explanation.
    • Fossils.  Past life was different from present life.  Extinct life could be classified into the same scheme used for extant creatures.  Here were more observations in need of explanation.
    • Diversity and Biogeography.  "Creation" was found to be different in different places.  Differences between areas are correlated with geographical isolation and, for fossils, with age.  Here are many more observations in need of explanation.
           [The biogeographical patterns that Darwin observed during the voyage of the Beagle -- including correlations between endemic island species and species on the nearest large land mass, and between extinct (fossil) species and extant species found in the same locality -- moved him toward an evolutionary perspective.]
    • "Clockwork Universe."  The whole idea of mechanistic explanation (i.e., that "natural" events have "natural" causes and can be explained by cause-and-effect relationships that do not involve supernatural powers) was probably necessary for an understanding of evolution.
           [A mechanistic worldview had been conspicuously successful in astronomy in the centuries before Darwin (Galileo died the same year that Newton was born, in 1642).  The rise of mechanistic explanation led to a proliferation of machines (e.g., clocks, pumps, windmills), eventually to steam engines and the industrial revolution.  Change in human societies became evident, and much of this change was seen as "progress".  Life also began to receive mechanistic explanation in the early 1600s, notably with William Harvey's theory that the heart works like a pump causing the circulation of blood, dramatically confirmed later that century by the microscopist Malpighi's discovery of capillaries.  Other discoveries in anatomy, physiology, and embryology followed.]

  • Certain prior ideas served as powerful organizing principles, but stood as obstacles to appreciating evolution.
         Science grew out of a scholarly tradition that shared a long heritage with Christian theology.  In that tradition scripture was widely accepted as authoritative on matters of objective fact.
         Even apart from religion, several biological theories and empirical observations have seemed inconsistent with Darwinian evolution.
    • "Young Earth."  The account of Earth's creation in Genesis and subsequent Biblical history suggests only a few thousand years between "creation" and present time.  In 1650, an Irish archbishop James Ussher used "cutting edge" biblical scholarship and theology to date the year of creation at 4004 B.C.  This date has become infamous as a target for ridicule, but at the time it represented a valiant effort to quantify the extent of history.
    • Noah's Flood.  The great flood recorded in the Bible (Genesis, chapters 6-9), provides a superficially satisfactory basis for explaining many dramatic features of the Earth's surface, including all sedimentary rocks as well as fossils of marine creatures high inland.  By extension, multiple (nonbiblical) catastrophes could be used to develop a more detailed geological record for times predating the arrival of man.
    • Fixity of species.  "Like reproduces like."  It is only common sense that a field sown in wheat does not produce oats, and that cats do not give birth to puppies.  This simple, everyday observation reflects a universal orderliness of nature that would begin to unravel if species could transform one into another.
    • Scala naturae.  This organizing principle held that all forms of life could be arranged into a single (unbranched) and progressive ladder of life, from primitive to complex (leading from rocks to plants and sessile animals to people and on to angels), was readily amenable to an evolutionary interpretation.  However, the linear and progressive quality of such "evolution", including ideas associated with Lamarck, created considerable interference with Darwin's ideas.
           [The confusion and conflation of Darwinism and "progress" continues to the present day, reflected in such terms as "primitive" or "lower" vs. "advanced" or "higher" forms of life.  Such terms have no place in a Darwinian view.]
    • Catastrophism.  The scientific theory that Earth has had several episodes of creation, each ending with a catastrophic destruction, was decidedly at odds with any direct, uninterrupted process of evolution (including both Lamarckianism and Darwinism).  Noah's flood was understood as the archetypal (and most recent) catastrophe, but catastrophism was solid science, not myth or theology.  Catastrophism was based on a crude but nonetheless accurate reading of fossil evidence, which truely records several catastrophes such as the great Permian and Cretaceous extinctions, which closed the Paleozoic and Mesozoic eras respectively.  These were each followed by a "new" and "advanced" biota.  Note that the evidence still stands -- these extinctions are currently understood as the result of asteroid impact or massive volcanism, which, although not extinguishing life and requiring a new creation, were indeed "catastrophes" which did significantly reset the stage for ongoing evolution.
    • Refutation of spontaneous generation.  Louis Pasteur finally laid to rest the idea of spontaneous generation in the mid 1800s, an idea which motivated some early evolutionary ideas (e.g., life is continually emerging, then progressing toward perfection, with the scala naturae resulting from the contemporary existence of many species at various stages of progress).  Thus the concepts of Omnis vivo e vivo and Omnis cellula e cellula seemed to refute evolutionary ideas.
    • Vitalism.  The idea that life involves some special essence, or "vital principle", has always seemed obvious to many observers of nature.  Vitalism renders mechanistic explanation inapplicable.
           [Vitalism has proven to be a moving target for refutation by science, and is still quite strong at the end of the 20th century.  After metabolism began to yield to chemistry (respiration and nutrition as chemical reaction), there remained the mysteries of heredity and development.  Since basic genetics has yielded to chemistry (i.e., DNA), and development is beginning to crack, there is still the mind.  Although most evolutionary biologists and neuroscientists believe that thought, memory, emotion and personality operate firmly within the domain of mechanistic explanation, that view does not prevail in the wider culture.  This may be the deepest difficulty between evolutionism and creationism, even between science and religion: the idea that evolution cannot explain, and may appear to deny, the concept of "soul" (which is often equated in popular thinking with the idea of "mind").  Even Alfred Russell Wallace was convinced that evolution could not explain the human mind, and so parted ways with Darwin and dabbled in spiritualism; see Richard Milner, "Charles Darwin and Associates,Ghostbusters", Scientific American, October 1996.]

  • [Students desiring a deeper discussion of issues related to the historical and/or current "conflicts" between evolution and religion should contact the instructor.  Extra sessions may be arranged if there is sufficient interest.  Alternatively, see Science and Religion (an essay recently published in Science) and then check out the many links available at National Center for Science Education.]