Human versus animal smell

There is no doubt that many animals have a sense of smell far superior
to that of humans. Most vertebrates (animals with backbones) have
many more olfactory nerve cells than humans. This probably gives them
much more sensitivity to odors. Also, the structure in the brain that processes
odors (called the olfactory bulb) takes up a much larger part of the brain in
animals than in humans. Thus, animals have a greater ability to process and
analyze different odors. This is why humans use dogs to find lost persons,
hidden drugs, and explosives—although research on “artificial noses” that
can detect scent even more reliably than dogs continues.
Still, the human nose is capable of detecting over 10,000 different
odors, even some that occur in extremely minute amounts in the air. Many
researchers are considering whether smell does not play a greater role in
human behavior and biology than has been previously thought. For instance,
research has shown that human mothers can smell the difference
between clothes worn by their baby and those worn by another baby only
days after the child’s birth.
Scientists are only beginning to understand the role that smell plays
in animal—and human—behavior. For example, animals release chemi-
cals called pheromones to communicate danger, defend themselves
against predators, mark territory, and attract mates.