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Week 2

Chapter 2: A History of Evolutionary Thought

Learning Objectives

  • Identify and describe the major developments in scientific thought that led to the discovery of evolutionary processes.

  • Explain how natural selection works and results in evolutionary change over time.

  • Explain what is meant by the "Modern Synthesis" and its impacts on evolutionary thought.

  • Discuss the teaching of human evolution in the U.S. and abroad.

The Beginnings of Evolutionary Thinking

  • Early human survival depended on understanding the physical environment:

    • Weather patterns, animal behavior, edible plants, medicinal plants, water sources, seasonal cycles.

  • Ancient cultures recorded their knowledge through:

    • Writings, hieroglyphics, and oral traditions focused on the natural environment and anatomy.

Major Historical Contributors

Aristotle (384–322 BCE)

  • Conducted systematic observations of animals and proposed biological classifications from his studies.

    • Published History of Animals detailing nearly 500 species based on:

      • Structure, physiology, reproduction, behavior.

  • Introduced the Scala Naturae (Great Chain of Being) placing humans closer to God.

Al-Jahiz (776–868 CE)

  • Wrote Kitab al-Hayawan (Book of Animals), introducing concepts of biological evolution 1,000 years before Darwin.

    • Discussed:

      • Struggle for existence, species transformation, environmental influences on species.

Ibn al-Haytham (965–1040 CE)

  • Known as the “Father of Modern Optics,” developed experimental methods in various scientific fields, influencing scientific investigation.

Western European Evolutionary Thought

  • Influenced by multiple scholarly traditions; developed more organized scientific thought during the 19th century.

Scientific Method and Taxonomy

  • Francis Bacon (1561–1626)

    • Codified the Scientific Method, emphasizing inductive reasoning based on observations.

  • John Ray (1627–1705)

    • First to publish a biological definition of species in Historia Plantarum.

  • Carl Linnaeus (1707–1778)

    • Developed binomial nomenclature and established modern taxonomy in Systema Naturae.

The Concept of Extinction

Georges Cuvier (1769–1832)

  • Proved species went extinct through fossil evidence, introducing the theory of catastrophism, contradicting existing beliefs.

James Hutton (1726–1797) and Charles Lyell (1797–1875)

  • Proposed uniformitarianism, suggesting gradual change over deep time leading to modern geology.

Jean-Baptiste Lamarck (1744–1829)

  • Introduced the Inheritance of Acquired Characteristics but was later disproven.

Darwin and Natural Selection

Key Events in Darwin's Life

  • Voyage on H.M.S. Beagle (1831-1836) led Darwin to gather data that influenced his theory of evolution.

Observations

  • Geographic and morphological variations influenced by environmental niches displayed within species like Galapagos finches, leading to Darwin's conclusions on natural selection.

Natural Selection Mechanism

  • Differential survival and reproduction driven by environmental pressures; variations leading to advantageous traits are passed down through generations.

  • Concept of evolution as descent with modification.

Major Influences on Darwin

Thomas Malthus (1766–1834)

  • Suggested that population growth could outstrip food supply, resulting in a struggle for survival—a key concept for Darwin's model of natural selection.

Modern Synthesis

  • Merged Darwinian evolution with Mendelian genetics between 1930 and 1950:

    • Defined evolution as changes in allele frequencies due to natural selection, mutation, migration, and genetic drift.

  • Promoted understanding of speciation as a result of selective forces and genetic changes over time.

Teaching Evolution in the U.S.

  • Historical resistance rooted in political and religious contexts.

  • Evolution's acceptance improved through the 21st century, with increasing incorporation into educational standards despite ongoing debates.

Misconceptions about Evolution

  • Common myths include:

    • Linear progression towards perfection; that evolution intends to create perfect organisms;

    • Misunderstanding of evolutionary fitness.

  • Modern examples of evolution in response to anthropogenic changes, like urbanization affecting species adaptation.

Review Questions

  • Describe major scientific developments leading to natural selection.

  • How does natural selection operate?

  • Importance of genetics in understanding evolution.

  • Identify current examples of evolution in various species.