: Examination of familiar farm animals like cows, pigs, sheep, and horses.

The narrative is divided into chapters that act as individual case studies for different species:

: Analysis of less traditional domesticated animals, including camels, reindeer, and laboratory rats.

: Francis details how selecting for a single trait— tameness —unintentionally triggers a suite of physical changes. These include floppy ears, shorter snouts, smaller brains, and unique coat colors, a pattern seen across diverse species from dogs and cats to reindeer and camels.