The Origin of Species · Chapter
Doubtful Species explained
Darwin explores the challenge of distinguishing between species and varieties, arguing that the boundary is arbitrary and that varieties are incipient species.
What happens
Darwin explores the challenge of distinguishing between species and varieties, arguing that the boundary is arbitrary and that varieties are incipient species. He uses examples from botany and zoology, including the work of H.C. Watson, Wallace, and De Candolle, to show that even experienced naturalists disagree on classification, and that intermediate forms blur the lines between individual differences, varieties, subspecies, and species.
Themes in this chapter
Variation and Inheritance
Darwin emphasizes that individual differences, varieties, and species form a continuum, with variation being the raw material for natural selection.
Natural Selection and the Struggle for Existence
The passage from one stage of difference to another is attributed to the cumulative action of natural selection and use/disuse of parts.
Domestication and Artificial Selection
Analogies to pigeon and poultry fanciers are used to explain how naturalists form judgments about species boundaries.
Characters to notice
- Charles Darwin
Author and narrator; presents his view that species and varieties are arbitrarily defined and that varieties are incipient species.
- Mr. H. C. Watson
Provided Darwin with a list of 182 British plants considered varieties but ranked as species by some botanists.
- Mr. Wallace
His papers on Malayan Archipelago animals are cited to illustrate the gradation from variable forms to representative species.
- De Candolle
His memoir on oaks is discussed, showing that even the best-known species have many varieties and that specific limits are often doubtful.
- Asa Gray
Quoted commenting on De Candolle's oak memoir, noting that characters used in specific definitions often vary on the same tree.
- Mr. Wollaston
Mentioned for his work on varieties of fossil land-shells in Madeira that persisted as varieties for long periods.
Key passages
“Hence, in determining whether a form should be ranked as a species or a variety, the opinion of naturalists having sound judgment and wide experience seems the only guide to follow.”
When deciding if a form is a species or a variety, the best we can do is rely on the judgment of experienced naturalists.
Darwin acknowledges the subjective nature of classification.
“A well-marked variety may therefore be called an incipient species; but whether this belief is justifiable must be judged by the weight of the various facts and considerations to be given throughout this work.”
A distinct variety can be seen as a species in the early stages of formation, though the evidence for this will be presented later.
Key statement linking varieties to the origin of species.
“From these remarks it will be seen that I look at the term species as one arbitrarily given, for the sake of convenience, to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety.”
I consider 'species' a convenient label for similar individuals, not fundamentally different from 'variety'.
Darwin's radical redefinition of species as arbitrary categories.