Hecht and Horowitz (2015) begin by tracing the evolutionary history of the domestic dog (Canis familiaris), the only domesticated species in the Canis genus. Dogs are closely related to the gray wolf (Canis lupus), with divergence estimates ranging from 50,000 years ago based on archaeology to 145,000 years ago based on mitochondrial DNA evidence.
The review highlights that domestication likely began when early humans selected docile proto-wolves who tolerated human presence. Over time, dogs were bred for functional roles such as hunting, guarding, and companionship. A parallel example comes from Dmitry Belyaev’s famous fox domestication experiment, where selective breeding for tameness transformed fox behavior and appearance within 40 generations.
In the 19th century, the rise of dog shows and breed standards shifted selection toward aesthetics. This led to an explosion of distinct breeds but also to the emergence of inherited diseases linked to exaggerated physical traits and restricted gene pools. Such conditions can cause pain or shorten lifespan, though purebred dogs have also become valuable models for naturally occurring cancers and genetic diseases shared by humans.
Overall, the study underscores the complex legacy of domestication: while selective breeding has created remarkable diversity in form and temperament, it has also contributed to significant health challenges for modern dogs.
Source: Hecht, J., & Horowitz, A. (2015). Chapter 1: Introduction to dog behavior. References: 221.
