Which traits have been selected in the development of different dog breeds?

The development of over 400 distinct dog breeds has been driven by the selective breeding of ancestral wolves for a wide variety of human-desired traits. These selections have focused on several key areas:1

• Temperament and Behavior: Early selection began with choosing wolves for companionable traits. Breeders continue to select for specific temperaments suited to the roles dogs play in human society.12
• Physical Appearance: Humans have extensively selected for specific fur colors, thicknesses, and lengths, as well as distinct body types.13
• Skeletal Structure and Gait: Many breeds were developed for specific physical tasks, resulting in unique skeletal adaptations. For example, the dachshund was bred with a long, low body for hunting in tunnels, while the greyhound was selected for speed and a flexible spine. Breeders have also selected for unique gaits, such as the German shepherd's "flying trot".4

While selective breeding has created diverse and specialized dogs, it has also led to concerns regarding genetic diversity and health. Intense selection for specific physical features—such as the compact, flat-faced appearance of French Bulldogs—can result in significant health issues, including breathing difficulties that negatively impact the animal's quality of life.1