Sense of Smell: Human Vs. Dog

Did you know that dogs have nearly 44 times more scent cells than humans? 

Humans have five to six million odor-detecting cells as compared to dogs that have 220 million cells. The reason for this difference? Humans have evolved to rely less on our sense of smell whereas most animals have retained this sense. 

Another fun fact about canines and smell : Dogs can distinguish non-identical twins but not identical twins based on odors.