The Origin of Species · Chapter
Sexual Selection explained
Darwin introduces the concept of sexual selection as a distinct form of natural selection that arises from competition among individuals of one sex (usually males) for mates.
What happens
Darwin introduces the concept of sexual selection as a distinct form of natural selection that arises from competition among individuals of one sex (usually males) for mates. He contrasts it with natural selection by noting that the outcome is not death but differential reproductive success. Darwin describes various examples of male combat and female choice across the animal kingdom, including alligators, salmon, stag-beetles, and birds, and argues that many secondary sexual characteristics—such as weapons, ornaments, and song—have evolved through this process. He also acknowledges that not all sexual differences can be attributed to sexual selection, citing the example of the tuft of hair on the wild turkey-cock.
Themes in this chapter
Natural Selection and the Struggle for Existence
Darwin distinguishes sexual selection from natural selection, emphasizing that the former involves a struggle for mates rather than for survival.
Variation and Inheritance
The chapter discusses how variations in weapons, ornaments, and behaviors are inherited, often sex-limited, and can be shaped by selection.
Characters to notice
- Charles Darwin
Author and primary voice; introduces and explains the theory of sexual selection.
- Pierre Huber
Referenced indirectly through the mention of M. Fabre, but Huber is not directly named in this excerpt.
- W. Herbert
Not directly mentioned in this excerpt; no character check-in applicable.
Key passages
“Sexual selection depends, not on a struggle for existence in relation to other organic beings or to external conditions, but on a struggle between the individuals of one sex, generally the males, for the possession of the other sex.”
Sexual selection is not about survival against predators or environment, but about competition among males to mate with females.
Darwin clarifies the unique domain of sexual selection.
“The result is not death to the unsuccessful competitor, but few or no offspring.”
Losing males do not necessarily die, but they leave fewer or no descendants.
Key distinction from natural selection.
“Among birds, the contest is often of a more peaceful character. ... successive males display with the most elaborate care, and show off in the best manner, their gorgeous plumage; they likewise perform strange antics before the females, which, standing by as spectators, at last choose the most attractive partner.”
In many bird species, males compete not by fighting but by displaying their plumage and performing courtship rituals, and females select the most appealing male.
Darwin describes female choice as a mechanism of sexual selection.