Passage – General Questions

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Passage Discussion

Paragraph One:

The opening paragraph introduces the passage’s two subjects, Charles Darwin and a group that refers to its view as “strict constructionist Darwinism.” The paragraph begins by presenting Darwin’s view that his theory of evolution was more than just the doctrine of natural selection, which Darwin stated was “the main but not the exclusive means of modification.” Next, the author introduces the strict constructionist Darwinists, who state that natural selection explains all biological phenomena, down to “every aspect of every species’ form and behavior.”

Paragraph Two:

Here, the author provides more background information about natural selection, explaining that natural selection results in “adaptation”, a term the author defines. The author points out that an implication of the strict constructionist view is that every attribute of every species, and that the very survival of every species, results from adaptation due to natural selection, and then the author counters that implication by indicating that nature offers “numerous examples” to the contrary.

Paragraph Three:

While conceding that natural selection does favor some random genetic mutations that improve a species’ reproductive success and disfavors other harmful attributes, the author states that “most mutations fall into neither category,” meaning that they neither improve nor worsen a species’ chance of survival. In fact, such neutral adaptations apparently account for “a large extent of the evolution of DNA.” Even though these neutral adaptations do, in fact, change the species’ attributes, the theory of natural selection does nothing to explain why they occur.

Paragraph Four:

In this final paragraph, the author presents an example from the field of paleontology that further weakens the strict constructionist view. Mass extinctions, and specifically the mass extinction of the dinosaurs 65 million years ago, do not fit the strict constructionist view that natural selection explains the success or failure of every species. The mass extinction of the dinosaurs probably resulted from the impact of an extraterrestrial body. Although it is likely the case that the extinction of the dinosaurs and the subsequent, relative success of mammals resulted from the mammals’ being better suited, biologically, to contend with the environmental conditions following the impact, the adaptations that lead to the mammals’ success and the dinosaurs’ extinction did not occur in anticipation of it or in preparation for it. In other words, the mammals’ success resulted from “dumb luck” rather than natural selection.

VIEWSTAMP Analysis

The Viewpoints presented in the passage are those of the Author, Charles Darwin, and the strict constructionist Darwinians.

The Structure of the passage is as follows:

• Paragraph 1: Introduce the views of Charles Darwin and the strict constructionist Darwinians, and state in general terms how those views conflict, while also foreshadowing the Author’s view that the theory advanced by the strict constructionists is incorrect.
  
  Paragraph 2: Provide more detail about natural selection and adaptation, generally. State an implication of the strict constructionist view, and introduce the Author’s use of evidence from nature, continued in the third and fourth paragraphs, to counter that view.
  
  Paragraph 3: Present evidence undermining the strict constructionist position, referenced in Paragraph 1, that natural selection accounts for “every aspect of every species’ form and behavior.” Specifically, the Author presents evidence that most DNA substitutions are nonadaptive.
  
  Paragraph 4: Provide additional evidence weakening the strict constructionist view. Specifically, in this paragraph the Author demonstrates that fortuitous circumstance, rather than natural selection, lead to the mass dinosaur extinction 65 million years ago and the subsequent success of mammals in the dinosaurs’ absence.

The Author’s Tone is critical, with the criticism directed toward the strict constructionists.

The Main Point of the passage is that the strict constructionist view is directly inconsistent with Darwin’s own statements regarding his doctrine of natural selection, and is incompatible both with modern research into the evolution of DNA and evidence concerning the mass extinction of the dinosaurs.