Stratigraphic Paleontology was the major use of fossils by the mid-19th century as the effort was made to correlate strata across Europe and to other continents. Studies of changes over time remained firmly in the framework of descriptive biostratigraphy without any widely accepted causal model. It was into this framework that the idea of evolution via natural selection was proposed by Darwin and Wallace. The impact of this idea is hard to overstate because it fundamentally changed the way species, taxonomy, the fossil record and the history of life would be viewed and interpreted.

As you read through these readings, there are four main themes to consider:

1. What was the pre-Darwinian view of the history of life and the turnover of species through time?
2. How did the proposed mechanism of natural selection work? How did it change our view of the history of life?
3. What was the immediate impact on paleontology? What kind of ideas and interpretations were possible?
4. What were the ideas of Neo-Lamarkism and Orthogenesis (the two leading models in the theoretical reaction against natural selection in the late 19th century)? How did paleontologists contribute to this reaction?

Harris sect. 22-23

Section 22 deals largely with Darwin and some of the immediate reactions to his ideas. Section 23 looks at the impact on paleontology and theory development through the “Modern Synthesis” that integrated natural selection, ecology, genetics, and paleontology around 1940.  Be sure to read these before tackling the readings.

Rudwick (1976) ch. 5, p. 218-260 

This is the final chapter from Rudwick’s book that looks at the impact of Darwin’s work. It includes some good information on the pre-Darwinian framework (sections I-IV) using the work of Henrich-Georg Bronn (introduced in section I) published just two years before “The Origin of Species” appeared. The following sections (sections V-IX) on Darwin and his impact include a discussion of the influence of Lyell, the initial problems his theory faced, how it rejuvenated paleontology, and the challenges that arose in the later 19th century. You can skip sections X and XII – they are reflections over the historical sweep of paleontology described in the entire book. Some notes on this selection:

The chapter just before this one includes some information on Richard Owen and his concept of “archetypes” that might be useful. An “archetype” was an common structural plan identified for each class of vertebrates. These werenot envisioned as “common ancesors”. Rather Owen presented them as more-or-less Platonic, idealized plans that were in the Creator’s mind which knew all the modifications to come – resulting in the directed development along Divinely ordained pathways. As you might expect, this concept did not fare very well over time.

Bronn and Owen are good representatives of some of the pre-Darwin ideas as paleontologists tried to grapple with the fossil record.  The opening sections are useful because they present how naturalists viewed the fossil record and the issues it raised – while you don’t need to follow all the details, the main point is the basic conceptual framework in the absence of a causal theory (sections II-IV). Note the similarities to Lyell some 25 years earlier.

Darwin’s idea had a long period of development. One of the main issues was how to reconcile his evolutionary ideas with geology and the fossil record (section V), with Lyell as one of his primary influences.

Sections VI and VII address some of the immediate reactions to natural selection, with Owen and Lyell being featured in Section VII.  The impact of evolution on paleontology as an explanatory model is made clear in section VIII notice how it led to rethinking of the relationships between species. Some of the problems that developed in the later part of the 19th century are discussed in Section IX – leading into the following reading.

Bowler (2003) p. 234-250 

Bowler has written widely on the history of evolutionary ideas – this chapter presents theory developments in the 1875-1925 time frame. We will consider p. 234-250 that describe the age of the earth controversy (topic of a future class) and some of the later 19th century rivals to natural selection – in particular Neo-Lamarkism and Orthogenesis which were favorites of paleontologists. (Feel free to read the remainder of the chapter on the Tree of Life approach, Neo-Darwinism, Mendalism and the rise of genetics if you wish.) The section on Neo-Lamarakism is a bit detailed, but the point is not all the variants on the idea (meaning don’t try to pin down all the allusions and subtle shifts of thought). Rather, ask yourself why was it attractive? Why did paleontologists seize on it and Orthogenesis as alternatives to natural selection?

To dos

• Pre-Darwinian framework (use Bronn’s work)
  • What was known about the turnover of species through time?
  • List the main features of Bronn’s synthesis (they are in there!).
  • Does the difference between phenomenological “laws” versus causal explanations make sense? (I find it analogous to the earlier distinction between natural history and natural philosophy.)
• Natural selection
  • Most or all of you have undoubtedly been through evolution via natural selection at some point (historical geology, paleontology, biology, etc.). If you are unsure of the mechanism, re-read section 20 of the Harris notes.
  • What was the influence of Lyell on Darwin’s thinking?
  • How did this idea change our view of species and relations between species (i.e., classification)?
• Impact
  • What was the impact on paleontology? How was the fossil record viewed differently?
  • List some of the leading “case studies” mentioned in Rudwick.
  • How did the idea of evolution and natural selection change how these were interpreted?
• Late 19th century decline of Darwinism
  • Why was the age of the earth controversy important in this context? (Note: we will look at it more closely in a few weeks.)
  • What were the main ideas of the Neo-Lamarkism and Orthogenesis theories? Why were they attractive?
  • How did paleontologists contribute to these theories?

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