History of Evolutionary Theory––#

HISTORY OF EVOLUTIONARY THEORY

  1. Introduction

    1. History helps us know where we’ve been and may keep us from repeating our mistakes
    2. It also provides a context for where we are today
    3. The history of evolutionary theory is extensive, complicated, and quite fascinating
    4. Here we will trace this history from the eighteenth century to today

  2. Pre-Darwinian history

    1. The Copernican revolution had removed earth from the center of the universe by the end of the 1600s
    2. But most Christians retained a “traditional view” of earth history until the middle of the 1700s

      1. Creation about 4000 B.C. in six literal days
      2. A world-wide flood that caused great disruption of the earth’s surface
      3. No change in species
      4. No extinction

    3. During the middle to late 1700s questions about this view became more common

      1. James Hutton, the Scottish geologist

        1. Studied geology of the British isles, particularly of Scotland
        2. Founded uniformitarianism––”No vestige of a beginning, no prospect of an end”

      2. Erasmus Darwin (grandfather of Charles Darwin)

        1. Wrote Zoonomia and other works; was a poet and freethinker
        2. Promoted view that organisms had changed over time

    4. Questions continued into the early 1800s.

      1. Geologists, many of them Christian clergy and virtually none of them “transmutationists”, began to trace out and map geologic formations
      2. They noticed that the rocks and the fossils they contained exhibited predictable order
      3. They developed the concept of the geologic column
      4. These advances in knowledge led to further speculation that

        1. The earth was very old
        2. Organisms had changed through time

      5. Influential people, books and ideas

        1. Cuvier’s work in vertebrate paleontology

          1. Multiple catastrophist
          2. Rejected notion of transmutation
          3. However, he showed that different types of vertebrates lived at different times

        2. Charles Lyell’s Principles of Geology (1830s)

          1. Data rich
          2. Attempted to establish the doctrine of uniformitarianism
          3. Also rejected transmutationist theories until later in life

        3. William Paley’s Natural Theology (1802)

          1. Watch implies watchmaker
          2. Made the “argument from design” popular

        4. Lamarck’s speculations on change

          1. Orthogenesis
          2. Inheritance of acquired characteristics

        5. Robert Chambers’ Vestiges of Creation (1844)

          1. Brilliently written but highly speculative
          2. Promoted view that organisms changed as a result of the inheritance of acquired characteristics as well as through an internal drive toward progress
          3. Had wide influence

  3. Influence of Charles Darwin (1809-1882)

    1. Voyage on the H.M.S. Beagle (1831-1836)

      1. Darwin found physical evidence for geologic change over extended periods of time. (He was influenced by Lyell’s Principles of Geology, a copy of which he had with him on the voyage)

        1. Rise of the Andes by tectonic activity
        2. Coral reef formation

      2. He also found evidence, particularly on the Galapagos Islands, suggestive that species were not fixed over time

    2. Upon his return to England he began to speculate on the possible causes of biological change

      1. He found the ideas of Erasmus Darwin, Lamarck and Chambers unacceptable, for they were backed by little or no data
      2. Upon reading the sixth edition of Thomas Malthus’ Essay on the Principle of Population in 1838, he began (about 1842) to develop a theory for a mechanism that would account for biological change--natural selection
      3. He was, however, reluctant to publish his views
      4. Moreover, he was busy working on other books on

        1. The voyage of the Beagle
        2. Coral reefs
        3. Barnacle systematics

    3. In 1857 he received a manuscript from a young British naturalist working in the Far East, Alfred Russell Wallace

    4. Like Darwin, Wallace had read Malthus
    5. Also, like Darwin, Wallace had travelled extensively
    6. Wallace’s manuscript contained a synopsis of his views on change––and they were almost exactly the same as Darwin’s!

      1. Organisms overproduced offspring
      2. Offspring exhibit heritable varability
      3. Some variants survive and reproduce more successfully than others

    7. Darwin was shocked.

      1. He was about to be scooped
      2. Friends arranged to have papers by both Wallace and Darwin read at the Linnaean Society meeting in 1858
      3. Darwin wrote feverishly for the next year, and his Origin of Species appeared in the autumn of 1859

        1. He described his book as “one long argument” which is what it is
        2. In it he tried to establish two points:

          1. Organisms changed over time
          2. Change occurrs by the process of natural selection

        3. Darwin’s book differed from that of his predecessors who had written on the topic of change in that Darwin backed up his views with a huge collection of facts from the natural world and from the world of domestic breeders
        4. Darwin

          1. Did not (until later) use the word “evolution” to refer to the changes he proposed
          2. Tried to avoid the notion of the progression of life from “lower to higher” forms which the term evolution implied

        5. The first edition sold out on the first day and was widely read

    8. In 1871, Darwin published The Descent of Man in which he developed his theory of sexual selection and extended the concept of evolution to humans

  4. Darwinism from 1859 to today

    1. Origin of Species immediately helped popularize the notion that organisms had changed through time
    2. Ironically, though, what Darwin considered to be his main contribution, the theory of natural selection, was broadly rejected

      1. The Victorians considered natural selection to be too revolutionary
      2. It was too materialistic and too much based on chance for people’s tastes
      3. Most people preferred to believe that progressive change was

        1. Preordained
        2. Directional
        3. Innate to all life

    3. Critics included

      1. Other “transmutationists”

        1. George Mivart

          1. Wrote On the Genesis of Species, a slam against natural selection
          2. Professed appreciation for Darwin privately, but panned his views in writing

        2. Samuel Butler

          1. A one-time friend of Darwin, became a bitter enemy
          2. Tried to resurrect Erasmus Darwin’s views

      2. Non-transmutationists

        1. Richard Owen

          1. Paleontologist and a dominant figure in British science
          2. Used his political advantage as a chief spokesman for English science to denounce Darwinism

        2. Charles Lyell

          1. Close friend of Darwin
          2. Could not buy Darwin’s theory until later in life

        3. Louis Agassiz

          1. Swiss-American zoologist/geologist at Harvard
          2. Established the notion of continental glaciation but rejected Darwinism

    4. Darwin did have influential friends who helped to promote his views, however

      1. Thomas Huxley
      2. Joseph Hooker
      3. Ernst Haeckel
      4. Asa Gray

    5. Indeed, as a result of Darwin’s book, most people, including most Christians, became convinced that

      1. The earth and life are very old
      2. Organisms change over time

    6. But by the end of the nineteenth century natural selection was far from universally accepted as the principle mechanism of change
    7. During the early 1900s, mutationalism became a major competitor for Darwinism
    8. Then from the 1920s to the 1940s, an influential group of biologists and paleontologists forged what is called the “synthetic theory of evolution”––or “neo-Darwinism”

      1. J. B. S. Haldane, Sewell Wright, Theodosius Dobzhansky, George Gaylord Simpson, Ernst Mayr
      2. United concept of natural selection with modern views of genetics
      3. Neo-Darwinism quickly became the orthodox view of evolution taught in virtually all textbooks

    9. Challenges to neo-Darwinism

      1. Saltational evolution and “hopeful monsters” (Richard Goldschmidt)
      2. Neutral theory of molecular evolution
      3. Theory of punctuated equilibrium (Eldredge and Gould)
      4. Theory of irreducable complexity

    10. Today, most people agree that natural selection plays an important role in microevolution, but there is considerable debate over the role that it plays above the population level
    11. It appears more and more likely that mechanisms other than natural selection play a bigger role in larger scale change

  5. Conclusion

    1. Thus, the history of evolutionary theory has not been as smooth as one might believe from reading a general biology text
    2. Indeed, evolutionary theory today continues to be revised, sometimes quite radically
    3. There is little doubt, however, that Darwinian natural selection will continue to play an important role in evolutionary theory, but other postulated mechanisms will take on greater and greater significance to evolutionary theorists