7.1 History of Evolutionary Theory

• Charles Darwin is the father of evolutionary thought.
• Charles Darwin developed a theory to explain:

  1. The diversity of Life on Earth
  2. How all organisms are related to one another
  3. How all organisms are related to the environments they live in
• Evolutionary Theory:

  1. All life forms are similar at a cellular and molecular level
  2. Evolution is the biological history of life on Earth
  3. Evolution is the process by which organisms change (evolve) over time
• Two main ideas of the natural world:

  1. Species were fixed, did NOT change over time (immutable)
  2. Earth is less than 10, 000 years old (young) and relatively unchanging
• Most Europeans, including Aristotle, accepted the idea that all living things had been created in their present forms and were immutable (they could not change and had not changed).
• Believed all natural phenomena developed through strongly held religious beliefs.
• James Hutton lived between 1726-1797
• James Hutton was the first to challenge the belief that the earth was young
• James Hutton supported uniformitarianism. Believed the earth formed by slow moving processes like erosion and sedimentation.
• James Hutton concluded the Earth took millions of years (not thousands), to form the current landscape.
• Charles Lyell lived between 1797 and 1875.
• Charles Lyell is the Father of modern day geology.
• Charles Lyell popularized and expanded on Hutton’s idea of uniformitarianism.
• Uniformitarianism Principles:

  1. Earth has been changed by the same processes in the past that are occurring in the present.
  2. Geological change is slow and gradual.
  3. Natural laws that influence these changes are constant and eternal, and they operated in the past with the same intensity they do today.
• Lyell’s theories directly challenged the belief in a very young Earth.
• Georges Cuvier lived between 1769 and 1832.
• Cuvier was a paleontologist.
• Paleontology: The study of fossil organisms to learn about prehistoric life.
• Georges Curvier compared fossils of modern day elephants to mammoths; conclude that some organisms had become extinct over time (e.g. Mammoths, Dinosaurs).
• Cuvier's Study of Paleontology:

  • Fossils of very simple organisms are found in all depths of fossil deposits
  • Fossils of more complex organisms are found only at shallower depths , in younger rock
  • Fossils in the shallower depths are more likely to resemble living species
  • Rock layers contain fossils of many species that do not occur in layers above or below them
• Fossil observation offered strong support that life evolved from simple to complex
• Cuvier believed that species themselves did not change
• Catastrophism: Global catastrophes, such as floods, caused the widespread extinctions of species.
• Cuvier believed that these species were then replaced with another newly created set of species
• George Louis Leclerc - Comte De Buffon lived between 1707-1788.
• George Louis Leclerc applied scientific methods to the detailed study of anatomy.
• George Louis Leclerc studied animal structures, considered their functions. Was puzzled by some features that that seemed to have no purpose. (E.g. he studied pigs’ toes – they have toes that don’t reach the ground).
• Carolus Linnaeus lived between 1708-1788.
• Carolus Linnaeus was the father of taxonomy.
• Linnaeus proposed that life changed over time.
• Erasmus Darwin lived between 1731-1802.
• Erasmus Darwin suggested that life might have evolved from a single original source.
• Jean-Baptiste Lamarck lived between 1744 and 1829.
• Lamarck first to offer a mechanism for the evolution of a species.
• Lamarck explained evolution as a process of adaptation. An inherited characteristic that improves an organisms ability to survive and reproduce in an environment.
• Lamarck was the first to propose a hypothesis to explain how changes in species happen. A suggested explanation of observations, which can be tested.
• Lamarck believed that structures an individual used became larger and stronger while structures that were not used become smaller and weaker. (E.g. Ducks strain their toes to swim, and thereby develop webbed feet).
• Lamarck believed that individuals could pass down characteristics they acquired during their lives. (E.g. if an adult giraffe stretched its neck during its lifetime, then its offspring would be born with slightly longer necks).
• Lamarck believed organisms continually (willingly) change and acquire features in order to be more successful in their environments.
• Lamarck made significant contributions to our understanding of evolution:

  1. All species evolve over time
  2. A species evolve in response to its environment and becomes better adapted to that environment
  3. Changes are passed on from generation to generation