Question

Passage A

For decades, evolutionary biologists and archaeologists have debated the precise geographic origin and timing of dog domestication. Recent genomic analyses of ancient canid remains have finally begun to clarify this evolutionary mystery, pointing toward a single origin in Eurasia where all modern dogs descended from an extinct population of Late Pleistocene grey wolves. The prevailing consensus suggests that this historic split occurred between 15,000 and 30,000 years ago, a period when global climates were in flux and human populations were primarily nomadic.

During this era, human hunter-gatherers and wild canids occupied overlapping ecological niches, frequently migrating across the same terrains in pursuit of large mammalian game. According to the active domestication hypothesis, direct human intervention was the catalyst for this transformation. Proponents of this view argue that early humans actively sought out wolf pups, adopting them into their communal groups. Within these bands, the young wolves were integrated into daily life, gradually learning to assist humans in tracking prey, retrieving game, and defending campsites from other predators.

Over subsequent generations, humans engaged in deliberate artificial selection. By actively choosing to feed and breed only the most cooperative, docile, and useful individuals, early humans systematically altered the canines' genetic trajectory. This selective breeding gradually suppressed the wolves' wild predatory instincts while enhancing traits beneficial to humans, such as vocal communication and social bonding. This intentional partnership yielded an extraordinary co-evolutionary advantage: human groups possessing these proto-canines became significantly more efficient hunters, securing a reliable protein source that helped them survive the harsh realities of the ice age. Ultimately, Passage A presents the dog as a product of human ingenuity—a wild beast systematically transformed through active husbandry and purposeful selection into a specialized companion.

Passage B

An alternative perspective on canid evolution challenges the traditional narrative that early humans deliberately engineered the transformation of wolves into dogs. Proponents of the "self-domestication" model argue that dogs did not emerge from human capture and active breeding, but rather domesticated themselves by adapting to a novel ecological niche created by human activity: garbage dumps.

As human populations began to establish semi-permanent or permanent settlements, they accumulated substantial mounds of organic waste, including animal bones and discarded food. This refuse represented a highly stable, concentrated food source for local wildlife. Wolves that possessed a slightly lower fear response—specifically, a shorter flight-initiation distance—could venture closer to these human encampments to scavenge without fleeing at the first sight of a human. Under these conditions, natural selection, rather than artificial breeding, drove the initial stages of canid divergence. The bolder, less stressed wolves had a distinct nutritional advantage over their more timid counterparts, enabling them to survive and reproduce at higher rates.

Over generations, this scavenging population became isolated from wild forest wolves. As they adapted to life near humans, they underwent a cascade of physiological changes known as "domestication syndrome," which includes reduced adrenaline levels, floppy ears, shorter snouts, and piebald coat patterns. These physical traits were not selected for by humans; they were genetic byproducts of selection for reduced fear and aggression. While humans eventually recognized the utility of these lingering carnivores for camp defense and pest control, this mutualism was an afterthought. The initial divergence of the domestic dog was an unplanned, evolutionary adaptation by wolves exploiting human-altered environments, demonstrating that domestication can occur without conscious human intent.

Which of the following claims about domestic dogs is supported by both Passage A and Passage B?