The sense of smell is not one of those things that sets us off from other animals. Birds do it. Fish do it. Even dinosaurs did it. Smell is what allows homing pigeons to find their way home, according to Canadian researchers. Other research indicates birds actually inherited that skill – and improved upon it – from the giant Tyrannosaurus rex.
Smell is what lets king salmon return from traveling throughout the Pacific Ocean to the stream where their lives began, where they spawn and die.
It's also what lets mosquitoes find you, even if you are half a mile away. And it's why flies find your lunch at every picnic.
There is some evidence that we owe far more to our sense of smell than just being able to tell the difference between a rose and an armpit. Smell is believed to be one reason mammals evolved larger brains, leading finally to humans, with the largest brain-to-body-mass on the planet.
Paleontologists at the Carnegie Museum of Natural History in Pittsburgh, Pa., used high-resolution scanners to study the skulls of rare 190 million-year-old mammals and found that the part of the skull that housed the olfactory system was significantly larger than in earlier animals. That led them to conclude that the first step toward the development of larger brains was an effort to improve the sense of smell.
We benefited from that, and it no doubt came in handy for our ancestors as they wandered through the jungle both as prey and predator. But in the 21st century we rely more on our vision and our hearing to guide us through life, and our sense of smell has taken a back seat.
Too bad, because smelling could save your life by warning you that the hamburger you were about to eat was rotten, or the wine you were about to consume was stale, or the person you were about to ask out was, well...
Other animals know better. Keller said he has been asked so often about dogs that he had to study them, even though "I have no idea about dogs," he said.
"What's clear is the number of sensor neurons that dogs have to perceive smells is much, much higher than in humans," he said. "In humans, it covers a tiny piece of surface on the top of the nose and in dogs it's a much bigger area. So that suggests, and I think it's certainly true, that dogs are more sensitive."
All you have to do to find that out for yourself is get down on all fours and crawl around where you can smell "that interesting odor information that a dog gets," he added.
Keller said one professor had his grad students do just that. They crawled all over the campus, following a chocolate trail. It was probably more effective than a lecture.