The evolution of an idea

• The Earth and all living things were once thought to be immutable (unchanging/divinely designed)
• Chevalier de Lamarck


  1744-1829
• Lamarck's proposed ideas


  • All species evolve over time
  • A species evolves in response to its environment and becomes better adapted
  • Changes are passed on from generation to generation
• Spontaneous generation


  The idea that living organisms arise from non-living matter
• Lamarck's theory is flawed as organisms can acquire many characteristics during life, but many features do not change in response to use
• Fossil formation


  1. Organism dies in an area that prevents decomposition, due to anaerobic conditions

  2. Buried & compressed under sediment layers

  3. Under high pressure, organic compounds are replaced by minerals (permineralized fossil)

  4. Eventually exposed by erosion or excavation
• Paleontology


  The study of prehistoric life through fossils
• Fossils were once thought to be recently living organisms
• Observations that did not explain fossils

  • Fossils were of unknown organisms, or species no longer living
  • No fossils of living species
  • Buried deep within rock formations
  • Often found in unexpected locations
• Georges Cuvier


  1769-1832
• Cuvier's observations


  • Simple organism fossils found in all depths
  • More complex fossils found at shallower depths, more likely to resemble living species
  • Rock layers contain fossils of many species that do not occur in layers above or below them
• Cuvier's observations supported the theory that life had evolved from simple to more complex forms
• Catastrophism


  Cuvier believed species did not change, but global catastrophes caused widespread extinctions
• Charles Lyell


  1797-1875
• Lyell's Principles of Geology

  • Earth has been changed by the same processes in the past & present
  • Geological change is slow & gradual rather than fast/catastrophic
  • Natural laws that influence changes, are constant & eternal, and they are operated in the past with the same intensity
• Uniformitarianism


  Lyell's theory that geological change is slow and gradual rather than fast and catastrophic