It is not by chance that dogs are widely trained to perform many specific tasks in different work environments.  Police dogs are an excellent example of how these animals' capacities can be beneficial for human societies.  The smell is the sharpest sense of a dog. For a long time, this extraordinary feature has been recognized through dogs' work in many police operations like in rescues, explosive artifacts detections, and toxic substances apprehension in airports. 

As a result of the evolutive process of Natural Selection, the number of olfactory receptors of a dog is much more superior to his human owner. A significant parcel of their brains is dedicated to this job to equip them with specific mechanisms to survive among other species. Moreover, his receptors work better. His sense of smell is more advanced and efficient in discriminate many things simultaneously, as the distinction of a diversity of people in the same room, including the smell of the ones that have been there before.

As a carnivorous species, dogs prodigious sniffing always evolved as a matter of survival and guidance in life. The dogs' prey drive instinct is strong evidence of how natural selection plays a role in calibrating these animals' olfactory sensibility favoring their physical conditions to grant them better chances to succeed. Therefore, their ancestors improved this sense to find food and other performances like sniffing an available mate and get healthy offsprings. Along the evolutive process, the dogs' brain structure has been improving, equipping them with millions of sensory receptors that work as powerful scanners capable of register every little information of a vast exterior world through the action of a tiny snout.  

Dogs are also territorial species whose ancestors lived in packs; The wild creatures of the past depended on their smell to remain in groups, recognize potential rivals members of other packs, and avoid predators. To preserve their domains, dogs became more perceptive to many smell variations like other dogs' urine. Through the smell of urine, dogs communicate many characteristics and demarcate their spaces. These reminiscent characteristics prevail in the behavior of the dogs that we know nowadays. They still strongly rely on their smell to interpret the known and unknown of any environment.

Compared to humans, the difference in the brain's dog anatomy is connected to the abilities that he intuitively performs in his daily activities.  Dog's sense of smell proves how species evolved over time, changing and acquiring more possibilities to ensure its preservation by adopting features tailored to their needs.