Origin of Species, by Charles Darwin

Chapter I:
Variation Under Domestication

Causes of Variability — Effects of Habit and the use or disuse of Parts; Correlated Variation; Inheritance — Character of Domestic Varieties; Difficulty of distinguishing between Varieties and Species — Origin of Domestic Varieties from one or more Species — Domestic pigeons, their Differences and Origin — Principles of Selection, anciently followed, their Effects — Methodical and Unconscious Selection — Unknown Origin of our Domestic Productions — Circumstances favourable to Man's power of Selection —