Chapter 1 Introduction to dog behavior

Dog evolutionary history What is a dog? The answer can come in the form of a description of the dog’s characteristic behavior, physical description, or evolutionary history. We will begin with the latter. The domestic dog, Canis familiaris, is a member of the Canidae family, genus Canis, along with such territorial social carnivores as the gray wolf (Canis lupus), the coyote (Canis latrans), and the jackal (e.g., Canis aureus and Canis mesomelas). The dog is the only domesticated species of the genus: that is to say, the only canid for whom artificial selection (selective breeding) by humans has usurped natural selection as a prime mover of the species. A debate rages about how long ago, and where, a distinct species of dog appeared, given conflicting evidence from archeological sites and genetic analyses. There is much more agreement on one point: that dogs descended from wolves. Canis lupus, the present‐day gray wolf, is the domestic dogs’ closest living ancestor, as both species are descended from some proto‐wolf some tens of thousands of years ago. Archeological evidence suggests that the divergence between wolf and dog began up to 50,000 years ago, with the advent of early human agricultural societies (Clutton‐Brock 1999). Whether the divergence was a singular, one‐ time event or whether it happened at different times and multiple locations is still in debate (e.g., Boyko et al. 2009; Larson et al. 2012; Thalmann et al. 2013). Genetic evidence, from mitochondrial DNA, suggests that wolves and dogs began diverging much earlier, even 145,000 years ago (Vilà et al. 1997). Dogs’ domestication probably began with a human interest in animals who were relatively docile, perhaps willing to approach—or at least not flee from or attack— humans. The social nature of canids contributes to their interest in others, as well as the proto‐dogs’ flexibility in seeing humans as nonthreatening. This hypothesis was famously tested by the geneticist Dmitry Belyaev by creating a kind of “domesticated” fox out of a Siberian farm‐fox population simply by selectively breeding only those who reacted without fear or aggression to human approach. Over 40 generations, he had created foxes which looked and acted in many ways like familiar domestic dogs (Belyaev 1979; Trut 1999). For millennia, dogs were bred for use for tasks (e.g. guarding and hunting) or as companions. Quite recently, in the 19th century, artificial selection began to be driven by an interest in creating pure breed lines, for show and competition in dog “fancies,” dog shows. Thus, the diverse array of breeds seen today is a result of specific breeding over the last century and a half for physical traits and temperament which suited the newly formed breed “standards” (Garber 1996). While some current dog breeds resemble ancient representations of dogs in art, no breed can be traced to those ancient dogs. As we will discuss, the diversification into breeds, some with exaggerated physical features, has led to the rise of inherited diseases which can be painful or even fatal (Asher et al. 2009). Isolated populations of purebred dogs now serve as useful models for naturally occurring cancers and diseases found in both humans and dogs (Breen & Modiano 2008).