You’ve no doubt heard before that, compared to other animals like dogs, our human noses are rather paltry. But a researcher suggests that line of thinking may be wrong.
Writing in Nature Neuroscience, John McGann from Rutgers University in New Jersey challenges the belief that we have a poor sense of smell. In particular, he noted how we once thought humans could only discriminate about 10,000 odors. In fact, that number is closer to a trillion, based on a study from 2014.
“Dogs may be better than humans at discriminating the urines on a fire hydrant and humans may be better than dogs at discriminating the odors of fine wine,” he writes.
The apparent misconception that we have a poor sense of smell was based on the size of our olfactory receptors, which transmit odor information to the brain. Previous research, particularly writings from French physician Paul Broca in 1879, suggested that the smaller size of our receptors relative to our brain compared to other animals was the culprit.
Not so, says McGann. He says there is no evidence that sense of smell is directly linked to the size of the olfactory bulb, and our sense of smell is just as good as that of other animals. He says we have a similar number of neurons to other animals, playing an almost equal role in identifying scents. His conclusion is based on previous research.
"One of my favorite experiments was [...] where they had human volunteers crawling around blindfolded in a park tracking odor trails," he told IFLScience. "That experiment mostly showed that people could indeed follow a scent trail and got better with training."
It may also be that we are sensitive to different smells than other animals. But our sense of smell is equally as important, such as communication and mate choice.
"For so long people failed to stop and question this claim, even people who study the sense of smell for a living," McGann said in a statement. "The fact is the sense of smell is just as good in humans as in other mammals, like rodents and dogs."
Broca’s claim in the 19th century was actually quite bizarre, suggesting that our smaller olfactory bulb allowed us to have free will and ultimately leading to the later incorrect claim.
“He concluded that the smaller relative volume of the olfactory bulb corresponded to the instantiation of free will in the frontal lobe,” writes McGann in his paper. “Through a chain of misunderstandings and exaggerations beginning with Broca himself, this conclusion warped into the modern misapprehension that humans have a poor sense of smell.”