Emergence of Evolutionary Thought

All cultures throughout history have come to contemplate "the big picture": where we came from and where are we going. Belief systems of all types have evolved to explain the unexplainable, but one unique system has recently accumulated an unprecedented paradigm of theories that stand up to rigorous logic and experimental testing. Science will never replace other religions, but the ground it is covering is often seen as an unholy encroachment to time honored traditions.

  1. Early Beliefs, Confounding Discoveries
    1. The Great Chain of Being
      1. The Greeks began a systematics of classification that led to a formal dendrogram (dirt to angels!).
    2. Questions from Biogeography
      1. Technological developments led to further and faster travel. Naturalists observed incredible diversity of life in their travels. How could such variety, which was endemic in many areas, have spread to corners of the earth without a trace?
    3. Questions from Comparative Anatomy
      1. The variation of homologous and analogous structures puzzled anatomists. Some said they were variations from the moment of creation, but what about vestigial structures (pelvic girdle in snakes, tailbones in humans)?

    4. Questions About Fossils
      1. Studies of sedimentary beds revealed that deposits had been laid down slowly, one above the other.
        1. The layers held recognizable remains or impressions of organisms–fossils. The arrangement of the layers suggested that different organisms had lived at different times.

      2. De Buffon’s explanation: Perhaps species originated in more than one place, and perhaps species became modified over time–evolution!
  2. A Flurry of New Theories
    1. Squeezing New Evidence Into Old Beliefs
      1. Georges Cuvier believed in an original creation of all species.

        He further suggested that the abrupt changes in the fossil record in different rock strata reflected the concept of catastrophism.

        1. After each catastrophe, fewer species remained.
        2. The survivors were not new species; it was just that their ancestors’ fossils had not been found.
      2. Lamarck formulated a theory of inheritance of acquired characteristics which the idea that simple forms had changed into more complex ones by a built-in drive for perfection up the Chain of Being. For instance, a giraffe stretching its neck to reach higher branches would result in longer necks in the offspring.
    2. Voyage of the Beagle
      1. As a child (early 1800s), Darwin was curious about nature, but in college he first pursued premedicine and finally received a degree in theology
      2. Darwin, age 20, sailed around the world as the ship’s naturalist.
        1. He was reading Lyell’s Principles of Geology, which proposed a theory of uniformity–the notion of a gradual, lengthy molding of the earth’s geologic structure.
        2. Thus, the earth was not thousands, but possibly millions of years old – enough time for evolution.
  3. Darwin’s Theory Takes Form
    1. Old Bones and Armadillos
      1. In Argentina, Darwin had observed extinct glyptodonts that bore suspicious resemblance to living armadillos; Darwin wondered if the present species had evolved from the extinct one.
    2. A Key Insight–Variation in Traits
      1. Thomas Malthus had suggested that as a population outgrows its resources, its members must compete for what is available; some will not make it.
      2. Darwin felt that if some normally variant members of a population bore traits that increased their survival, then nature would select those same individuals to survive, reproduce, and possibly change future populations’ traits.
        1. On the Galapagos Islands, the dozen or so species of finches all varied from one another to some extent but resembled the mainland finches to some degree also; perhaps they had descended from common ancestors.
        2. Darwin reasoned that a population is evolving when its heritable traits are changing through successive generations.
      3. In 1858, Darwin received a paper from Alfred Wallace, who had developed the same theory of natural selection independently of Darwin. Wallace had been travelling throughout present day Indonesia.
      4. Darwin and Wallace presented a joint paper but Darwin published (alone) his ideas in book form in 1859.
      5. The book was entitled: On the Origin of Species or the Preservation of Favoured Races in the Struggle for Survival.
      6. "Origin" went through several revisions, each omitting critically shortsighted elaborations.
    3. Darwin saw evolution of one kind into another as happening gradually, in small increments, over hundreds or thousands of generations.
    4. It is crucial to note that Darwin had no knowledge of either Mendelian or molecular genetics to support or guide his theory. Some say that this is direct evidence of the weakness of evolutionary theory, but Darwinists have considered this the greatest strength.
    5. Today, we have expanded and modified the theory to include recent evidence: The Modern Synthesis.
    6. "Evolution" is now separated into two semantic divisions: microevolution (change within a species) and macroevolution (change from one species to another). This seems to have been done to divide religious opposition. Now another division "human evolution" seeks to again divide the shrinking religious opposition from what seems undeniable by even the most uniformed.
    7. The possibility of transitional forms was illustrated when, in 1861, fossil evidence of Archaeopteryx was unearthed.
      1. This animal appears to be a transitional form between reptiles and birds. Like birds, it was covered with feathers; but like reptiles, it had teeth and a long, bony tail.