Evolutionary Theories and Thinkers

Theory / Thinker

Creationism

  • Main Idea: Life was created by a divine being and does not change.

  • Key Points:

    • Species are fixed.

    • Based on religious belief.

  • Weakness / Limitation:

    • Could not explain fossils, extinctions, or new species.

Aristotle – Scala Naturae

  • Main Idea: Life forms arranged in a hierarchy from simple to complex.

  • Key Points:

    • “Great Chain of Being”.

    • Species are fixed.

  • Weakness / Limitation:

    • No idea of evolution or change over time.

Lamarckism (J.-B. Lamarck)

  • Main Idea: Organisms change by using or not using traits; changes are inherited.

  • Key Points:

    • “Use and disuse”.

    • “Inheritance of acquired traits”.

  • Weakness / Limitation:

    • No evidence for inheritance of acquired traits.

Catastrophism (G. Cuvier)

  • Main Idea: Earth’s changes due to sudden disasters.

  • Key Points:

    • Explains fossil layers and extinctions.

  • Weakness / Limitation:

    • Doesn’t explain gradual change or how new species form.

Uniformitarianism (Hutton & Lyell)

  • Main Idea: Earth changes slowly and continuously (e.g., erosion).

  • Key Points:

    • Earth is very old.

    • Processes today happened in the past.

  • Weakness / Limitation:

    • Doesn’t explain biological change directly, but influenced Darwin’s thinking.

Natural Theology (W. Paley)

  • Main Idea: Complexity of life proves existence of a designer.

  • Key Points:

    • “Watchmaker” analogy.

    • Life shows purpose and design.

  • Weakness / Limitation:

    • Doesn’t explain how species change or why some go extinct.

Erasmus Darwin / Transmutation

  • Main Idea: Species can gradually change over time.

  • Key Points:

    • Early idea of evolution.

    • Life shared common ancestry.

  • Weakness / Limitation:

    • No mechanism for how evolution happens.

Georges-Louis Leclerc, Comte de Buffon

  • Main Idea: Species can change over time and have common ancestors.

  • Key Points:

    • Earth is older than previously thought.

    • Species adapt to their environments.

  • Weakness / Limitation:

    • Did not provide a mechanism for evolution.

Key Figures in Darwin’s Life

  • Robert FitzRoy: Captain of the HMS Beagle.

    • Role: Provided Darwin the opportunity to travel the world and make observations that led to his theory of evolution.

  • Alfred Russel Wallace: Independently conceived the theory of evolution by natural selection.

    • Role: His paper, jointly published with Darwin, prompted Darwin to publish On the Origin of Species.

  • Charles Lyell: Geologist who advocated for uniformitarianism.

    • Role: His ideas about gradual geological change influenced Darwin’s thinking about biological change over long periods.