The Origin of Species · Chapter
Divergence of Character explained
Darwin introduces the principle of divergence of character, explaining how slight differences among varieties can be augmented into the greater differences between species.
What happens
Darwin introduces the principle of divergence of character, explaining how slight differences among varieties can be augmented into the greater differences between species. He draws analogies from artificial selection by fanciers and breeders, and argues that in nature, the more diversified the descendants of a species become, the better they can exploit diverse ecological niches, leading to increased numbers and the formation of new species.
Themes in this chapter
Variation and Inheritance
The chapter explains how small variations in domestic breeds and natural varieties accumulate through selection, leading to divergence and ultimately to species-level differences.
Adaptation and the Utilitarian Doctrine
Darwin argues that diversification of structure is advantageous because it allows organisms to exploit different resources and habitats, increasing their chances of survival and reproduction.
Characters to notice
- Milne Edwards
Darwin references Milne Edwards' work on the physiological division of labour as analogous to the advantage of diversification of structure in inhabitants of the same region.
- Mr. Waterhouse
Waterhouse is cited for his observation that Australian marsupials feebly represent carnivorous, ruminant, and rodent mammals, illustrating an early stage of diversification.
- De Candolle
Alph. de Candolle's work on naturalisation is referenced, noting that floras gain proportionally more new genera than new species through naturalisation.
- Asa Gray
Darwin cites Dr. Asa Gray's Manual of the Flora of the Northern United States to provide data on naturalised plants and their diverse genera.
Key passages
“Nevertheless according to my view, varieties are species in the process of formation, or are, as I have called them, incipient species.”
Darwin states that varieties are essentially species in the early stages of development, or 'incipient species'.
This is a core statement of Darwin's view on the continuity between variation and speciation.
“The more diversified in habits and structure the descendants of our carnivorous animals become, the more places they will be enabled to occupy.”
The greater the diversity in habits and structure among the descendants of a carnivorous animal, the more ecological niches they can fill.
This illustrates the principle of divergence through ecological opportunity.
“The advantage of diversification of structure in the inhabitants of the same region is, in fact, the same as that of the physiological division of labour in the organs of the same individual body.”
The benefit of structural diversity among organisms in a region is analogous to the division of labour among organs within a single body.
Darwin draws a parallel between ecological specialization and physiological specialization, referencing Milne Edwards.