Compared with other mammals in the Animal Kingdom, the human sense of smell seems to be much maligned. But is this reputation unfounded?
New research suggests that our olfactory receptors may be as powerful as those of dogs and rodents, putting a question mark over nearly 150 years of scientific understandings.
John McGann, of Rutgers University in New Jersey, has spent the last 14 years studying the olfactory system and has recently concluded that the human sense of smell might not be as underpowered as we initially thought.
Although often undervalued when compared to our other senses, certain smells can greatly affect our moods or provoke memories while losing our sense of smell can be an early sign of an oncoming illness.
Despite this, the human sense of smell has always suffered from a poor reputation and McGann points the finger of blame at a 19th Century brain surgeon name Paul Broca for propagating this school of thought.
Broca concluded that unlike other mammals such as dogs and rats, the size of the human olfactory bulb is smaller in relative terms to the rest of our brain volume and therefore our sense of smell must be inferior. Broca then determined that the compromise of this smaller olfactory bulb was an expansion of our frontal lobes and higher reasoning centres.
In comparing the olfactory bulb and brain sizes of humans and mice McGann found that in absolute terms the human bulb is larger than many mammals, who all carry a similar number of olfactory neurons that enable smells to be identified.
“For so long people failed to stop and question this claim, even people who study the sense of smell for a living,” he said. “The fact is the sense of smell is just as good in humans as in other mammals, like rodents and dogs.”
“We’d have two odours that mice couldn’t tell apart, expecting humans wouldn’t be able to, and they’d be like ‘that’s one and that’s two’,” he said. “It was amazing how good the human olfactory system was.”
However, there are some scientists, like Alexandra Horowitz from Barnard College, who believe there is still a wide disparity between our sense of smell and our canine friends:
“That there are olfactory specialists, such as perfumers or animal trackers indicates that with attention, we can get much better,” she added. “But not dog-level.”