Chapter 2. The Evidence for Evolution

  • Why is this chapter necessary?  Why was evolution a problematic idea in the 19th century?
    • Evolution is a materialistic explanation of diversity and adaptation, contradicts creation myths (remember that there are many.)
    • Large scale evolution cannot be observed directly, must be inferred.
    • Evolution contradicts "common sense".
  • 1859 marks the Darwinian revolution, but revolutionary theory had many antecedents. See Box 2.1.
  • Pre 1750 (roughly), prevailing assumptions were that
    • Humanity is at the center of creation and is its purpose
    • Species were created independently
    • Species do not change over time (they are immutable)
    • The creation event was recent (4000-10000 years ago?), and the earth is therefore young.
    • Our text calls this the "Theory" of Special Creation", but is it really a theory?
  • Contrast this with the modern view:
    • Homo sapiens is one of millions of species that have evolved
    • Species were not created independently - they are all related through descent
    • Species change over time, a little bit or a lot.
    • The world (and life) is very old: 4.5 and 3.8 billion years, respectively
  • Change through time: species are mutable
    • Direct observation
      • Development of resistance to antibiotics and antiviral drugs (HIV a spectacular example)
      • Change in complex morphological traits, e.g. soapberry bugs, Fig. 2.1
      • Development of heavy metal resistance in grasses on mine tailings.
  • Vestigial traits imply that organisms have histories:
    • Morphological examples:  wisdom teeth, vermiform appendix, eyes in sightless cave fish, erectile hairs in humans, extra digit in chickens, etc.
    • Molecular examples
      • Junk DNA
      • pseudogenes descended from functional genes through accumulation of loss-of-function mutations.  Many examples in genomes.
  • Fossil record: orderly, shows transitional forms (e.g. whales, dinosaurs to bird sequences.)  This is not what we would expect from the Flood (but why are we concerned with the Flood?)
  • Homology: See Fig. 2.11 for a classic examples involving the vertebrate limb.
    • Pre-evolutionary view (e.g. Owen): same organ in different animals/plants devoted to different functions.  Reflects plan of Designer.
    • Evolutionary view (e.g. Darwin): homology reflects descent with modification from a common ancestor.
    • Molecular homology
      • Genetic code - nearly universal, yet arbitrary.
      • Mutations shared with close relatives (CMT1A repeat, Fig. 2.16; processed pseudogenes, Fig. 2.17)
  • The world (and life) is very old
    • Geology 1790-1820 saw resolution of several controversies
    • Neptunists vs. Vulcanists
    • Hutton and Lyell showed that rocks have many origins (sedimentary, igneous, metamorphic)
    • Present day (observable) processes account for geological features (doctrine of uniformitarianism - note application to evolution)
    • This implies that the earth is very old:  "No vestige of a beginning, no prospect of an end"  (Hutton).
    • Development of techniques (relative and absolute) for dating rocks established the geologic column.
    • Sequence suggested by relative dating has been confirmed by radiometric (absolute) dating.
    • Fossil record was seen to be orderly, same sequence of forms in geologic sections throughout the world (e.g. fossil birds do not occur in rocks older than those containing the oldest fossil fish).
  • So what about those creationists?
    • Creationism spans a range of positions:
      • Young Earth Creationism (associated with Biblical literalism)
      • Old Earth Creationism
      • Intelligent Design (this is the latest scam – be warned)
    • Two forms of materialism  (= naturalism):
      • Ontological materialism: matter is all there is.
      • Methodological materialism: whether or not matter is all there is, I will assume this in doing science.
      • Freeman and Herron say that scientists must be methodological materialists, attitude toward ontological materialism is a matter of choice. Does this fix the creationism problem?