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Darwin
Origin of the Species
Why read Origin?
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Darwin’s Origin of the Species is seminal to the development of evolutionary
thought.
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Scientists generally agree that no one has influenced the modern scientific
world view more than Darwin (Moore; Locke; Mayr)
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Origin of the Species is still often referred to during the frequently
contentious debates in parts of our nation concerning the appropriate ideas
to be taught in public schools
However, surprisingly, Moore cites Korey’s research that indicates few
people have actually read the book.
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As further evidence, Moore states that “not one of the more than 500
students in [his] biology classes during the past four years has read it,” and
moreover, his polling of several scientists “suggests that no more than
approximately one in ten biologists has read the book” (107).
Edition
• We use the Oxford World Classic version of the text because it is
based on Darwin’s second edition.
• Darwin made several revisions between the first publication in 1859
and the sixth in 1872.
• The later editions thus differ considerably from the first, and the last
edition contains an additional chapter (chapter 7) dealing with
objections to the theory.
• These changes tend to obscure the original argument.
• The second edition was published just six weeks after the first
edition, limiting Darwin to only a few revisions in the content of the
original but allowing for the correction of some misprints.
Plethora of Details
• Does Origin seem to drown you in details?
• Darwin considered the book a brief treatment of the subject and
initially planned a more complete work later on.
• Even after over twenty years elapsing from the completion of his trip
to South America to collect data in 1837 and the publication of
Origins in 1859, he still was not quite ready to present his case.
• However, he felt compelled to make some of it available to the
public: “My work is nearly finished; but it will take me two or three
more years to complete it, and as my health is far from strong, I
have been urged to published this abstract” (3).
Structure of a Proposal Argument
• Begins with an introduction that describes a problem and
ends with a succinct statement of solution
• A body section providing a detailed explanation of the
solution
• A body section that summarizes and rebuts opposing
views
• A justification section, in which the writer provides the
reasons why the solution should be enacted.
• The conclusion sums up the key points but also attempts
to move the reader to accept the proposal
Are we imposing a structure of
Darwin that he didn’t intend?
• Locke asserts that "Darwin in his typical nineteenth-century
education would have been exposed to abundant examples from
classical authors employing the pattern and indeed would have had
training in the use.”
• “Darwin would have made use of such a pattern for his work, which
he himself describes as ‘one long argument’” (Locke 89).
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• This overview relies heavily on the discussions of Locke (87-89),
Bowler (114-25), and Moore, but Bowler’s schema works better to
illustrate Origin as a proposal argument than Locke’s (Locke
restricts his analysis to the classical structure, leading him to note
that chapters 10-14 are logically a digression, which “Cicero allows
but rather disapproves of”; Bowler, on the other hand, suggests
these chapters serve the necessary purpose of justifying Darwin’s
argument).
Introduction to Origins
• Darwin begins by describing the problem: although
some naturalists may have concluded previously that
“each species had not been independently created, . . .
such a conclusion, even if well founded, would be
unsatisfactory” unless a means could be found to
account for how such changes could have occurred (4).
• Then, after giving an overview of the book, he proposes
his solution that species evolve as “lineal descendants of
some other and generally extinct species” and that the
process occurs through the mechanism of natural
selection (7).
Explanation of His Solution
Chapters 1-5
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Darwin devotes the first third of his book to his detailed explanation of his solution of
the problem: species evolve through natural selection.
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In the first chapter (“Variation under Domestication”), the author discusses the
familiar success of animal and plant breeders in working with domesticated species
(he gives particular attention to the breeding of pigeons, a very popular pastime in
England at the time). His main point is that individual variation is due to artificial
selection--the breeder directly influences the reproductive process by changing
conditions.
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Then, moving to argument from analogy after establishing this commonly
acknowledged fact, in the second chapter (“Variation under Nature”), Darwin argues
individual variations also occur in the wild populations due to the “selection” of
changing natural conditions. In this chapter Darwin also takes great pains to point out
that naturalists often disagreed as to whether a particular form was a variety or a
distinct species. This confusion, Darwin says, is easily done away with if we come to
understand that varieties are merely an intermediate step in the production of new
species. The term "species" is thus an arbitrary one: a species is just a strongly
marked variety that the majority of experienced naturalists agree to call a species.
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From there Darwin transitions to the next chapter (“3: Struggle for
Existence”), whose central concept was adapted from the "principle of
population" that Malthus applied to human society. All species tend to overreproduce. When more individuals are born than can possibly survive, they
must compete for the scarce resources necessary to keep themselves alive.
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In the fourth chapter (“Natural Selection”), Darwin describes the mechanism
of Natural Selection directly. In the struggle of individuals of a species for
limited resources, a variation that makes one better able to exist within any
changing conditions will enable that individual to survive and reproduce
while the others of the species without that variation will die out. Thus, that
individual will start a line of variant from the extinct original species, and
after thousands of years of this process, what seems to be a new species
will have emerged.
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In "Laws of Variation" (chapter 5), he insists that although we may not know
what has caused a variation, nonetheless all changes of structure result
from a specific cause.
Responding to Opposing Views
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In the middle third of the book (chapters 6-9), Darwin anticipates and
responds to the many objections that will be raised against his theory.
Here he acknowledges potential concerns about his theory, such as the
apparent lack of transitional forms between known species, an explanation
for species with peculiar habits or structures, its assumed inability to
account for the production of organs of great complexity, like the eye
(“Chapter 6: Difficulties on Theory");
its negation of Lamarck's claim that instinct is a learned habit that had been
built into the species' hereditary constitution (“Chapter 7: Instinct");
the failure of distinct species, when crossed, to produce fertile offspring
(“Chapter 8: Hybridization");
and the fossil record did not seem to support his concept that evolution
always takes place slowly and gradually (“Chapter 9: On the Imperfection of
the Geological Record").
To each of these issues, Darwin provides a detailed rebuttal (some even
characterize it as tedious), replete with numerous examples from his and
other naturalists’ observations
Justification of His Proposal
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In the last third of the book (chapters 10-13), Darwin presents the justification for his proposed
solution. He effectively argues that his theory of common descent by adaptive modification
logically accounts for a wide range of otherwise inexplicable phenomena.
Rather than disproving evolution, once we understand why the fossil record is imperfect, we
realize that the known fossils are distributed just as we would expect on the basis of a theory of
common descent (“Chapter 10: On the Geological Succession of Organic Beings");
the existence of unique groups of species can be understood in that rising and falling masses of
land created routes for the dispersal of species and subsequent barriers to migration (“Chapter 11:
Geographic Distribution”);
oceanic islands life such as the Galapagos were populated by birds, wind, and other natural
forces carrying seeds and eggs occasionally across wide stretches of ocean (“Chapter 12:
"Geographic Distribution [Continued”]);
and that phenomena which naturalists have difficulty classifying satisfactorily can be made
explicable only in terms of a theory of common descent, that the fact that the embryos of different
animals often show a much greater degree of resemblance than the adults can be explained on
the assumption that adaptive modifications are produced mostly by changes in the later stages of
growth, leaving the early pattern of development unchanged, and that the existence of
rudimentary or atrophied organs, which are of no apparent use and which often never develop
beyond a vestigial stage, can be explained adequately only in that they are relics of once useful
structures, now declining because the changing habits of the species have rendered them
superfluous (“Chapter 13: Mutual Affinities of Organic Beings; Morphology: Embryology:
Rudimentary Organs").
Origin’s Conclusion
• Darwin uses his final chapter (“14: Recapitulation and
Conclusions") to sum up his entire argument.
• In the final paragraph, he uses the metaphor of the
"tangled bank" to describe the complex interrelations of
all of life and then ends the book with his assertion of the
"grandeur of this view”: “life, . . . having been originally
breathed by the Creator into a few forms or into one; and
. . . from so simple a beginning endless forms most
beautiful and most wonderful have been, and are being,
evolved” (396).