The Role of Olfaction in Dogs: Evolution, Biology, and Human-Oriented Work.

Dogs show exceptional olfactory sensitivity and are widely used in medical, rescue, military, and forensic applications, yet the determinants of individual and breed-level scent-work performance remain incompletely characterized. This review integrates evidence from the anatomy and physiology of the canine olfactory organ, neurobiological mechanisms of odor transduction and coding, and links between olfaction, memory, and emotion, alongside molecular genetics, evolution, domestication, and selective breeding. We synthesize findings indicating that complex nasal turbinates and specialized airflow patterns enhance odorant capture, while olfactory bulb circuitry and downstream connections to limbic and frontal networks support discrimination, learning, and affective modulation. Comparative and breed-focused studies suggest that skull morphology and breeding priorities can alter olfactory capacity, with shortened nasal anatomy associated with reduced functional potential in some lines. In applied contexts, detection success is strongly shaped by behavioral traits such as motivation, persistence, independence, and reward value, as well as by physical condition and environmental stressors that can impair search efficiency. Emerging literature further suggests that the gastrointestinal and upper airway microbiome, together with diet, housing, temperature, and workload, may influence sensory and cognitive readiness, although direct causal links to detection outcomes remain limited. Overall, canine olfactory performance reflects interactions among genetic-anatomical capacity, neurobehavioral factors, and environment, underscoring the value of standardized selection, training, welfare management, and future integrative research.