Final answer:
The self-domestication theory suggests ancestral canids became domestic dogs by scavenging around human settlements, benefiting from a calm temperament and a submissive hierarchy that made them well-suited to live alongside humans, which led to their domestication through selective breeding.
Step-by-step explanation:
The self-domestication theory suggests that ancient canids became domestic dogs primarily because tamer canids benefitted from scavenging around human settlements. As canids are highly social scavengers, those with traits such as a calm temperament, smaller body size, and hierarchy that included submissive behaviors had an advantage in a human-dominated environment. Over time, humans selected for traits that would be beneficial, such as loyalty, attentiveness, and reduced aggressiveness, forming a symbiotic relationship and leading to the domestication of dogs. The various roles dogs play, such as guarding, herding, hunting, and companionship, have been culturally significant and have evolved through selective breeding.