You smell better than your dog. Not a high bar, perhaps, if your dog like mine considers rolling on dead birds the pinnacle of existence. But on the other side of the sniff, your nose ‒despite the bloodhound’s well-deserved reputation for olfactory legerdemain ‒ might be equally talented.
            Consider an experiment I wish I’d thought of. Berkeley researchers dipped twine in chocolate and laid it in patterns across a grassy field, then asked student volunteers to follow the trail on all fours, using only their noses. They wore blindfolds, earmuffs, knee pads and thick gloves to make sure no other senses could chime in.
            Sniffing like bloodhounds, two-thirds of thirty-two subjects were able to follow the chocolate scent to the end of the trail within three attempts. All volunteers zigzagged along the trail in the same way that tracking dogs follow a scent.
            The researchers then trained four of these volunteers to see if they could improve. All were able to double their speed along the track within just a few days and deviated much less from the scent trail than on their first attempts.
            “Our sense of smell is less keen partly because we put less demand on it,” said Jess Porter, lead author of the study. “But if people practice sniffing smells, they can get really good at it.”
            In fact, we’re already really good at it ‒ we just think we’re not. We all pay attention to our senses, of course. We admire a musician’s trained ear, or a birder’s, and envy friends with eagle eyes who see things as clearly at twenty feet as we do at ten. (For actual eagles, that would be twenty and four.) We marvel at the blind learning Braille, their fingertips telling them things ours don’t, or gourmands distinguishing subtleties in food and drink that escape the rest of us.
            But smell gets no respect. Think about it: you have the innate ability to detect someone barbecuing half a mile away, a tiny gas leak, an approaching storm. And smelling those things ‒food, danger, weather ‒ has been important to us for a long time, so it makes sense we’d be experts. We’ve been smelling the world since well before we had words to describe its pleasures and perils.
            This includes the ultimate danger. Years ago, a woman killed herself in a parking lot near my home. I’d seen the car Tuesday in a far corner of the lot and assumed it was abandoned. My golden retriever showed some interest, tiptoeing around, but he picked up his tennis ball when I called and galloped back for another throw. Friday after dinner I walked out again, dog spinning and barking, and threw a ball as far as I could into the twilight. He streaked after it, and my eyes, following, focused on the car. There were three people standing around it, arms folded as if the evening had turned cold. They were facing different directions, and they looked lost. Walking closer, I noticed flies bumping the car windows and an unmistakable smell, one that farmers know but not most suburbanites. Gas companies add this odor to warn of leaks, knowing it touches our oldest selves and we’ll rise from our beds without knowing why, bodies for once speaking directly to the world.
            At the other end of existence, smell is the only fully developed sense we have in the womb, and it remains primary until around age ten, bypassing the filters and waystations our brain uses to let our other senses make sense. “One of the things that makes smell distinctive,” explains one researcher, “is that olfactory information is not rooted through this ‘switchboard’ structure called the thalamus on the way to other ‘thinking’ brain regions.” Instead, it goes straight from the olfactory bulb to our limbic system, which includes regions tied to emotion and memory. A current theory proposes that odors stimulate the brain to make new neurons in those areas, so it isn’t surprising that a diminished sense of smell has been linked to schizophrenia, depression, and Alzheimer’s.
            That express lane to you-beneath explains why memories so often seem to come from nowhere. A whiff of a former flame’s perfume, your grandfather’s tobacco or that mimeograph from middle school can transport you instantly, like Proust’s madeleine, across all the miles and years.
            We all have those moments. I stepped out one morning in eastern Virginia, bright and dry, fifty heading for seventy, and got a lungful of Scotland. It was unsummoned, probably some plant blooming nearby, and instead of standing with my keys in the carport, I was on a street in Edinburgh ten years earlier, cold stones and water nearby. It lasted just a few seconds but was more real than whatever I was thinking about a minute earlier, or anything I did the rest of the day.
            Why then is smell the poor cousin of the senses? Half of all people aged sixteen to thirty say they’d give up their ability to smell before their phone or laptop. But we can do some amazing things with those noses. You know your friends and relatives by smell, embodied (literally) in sweat. Married couples can pick out each other’s scents blindfolded, and even if you’ve been apart more than two years, you can still recognize your brother’s or sister’s unique odor print, the signature mixture of chemicals floating off their bodies. And your body, too: Adults in a 1989 study were able to identify their own t-shirts out of 100 identical shirts worn by others.
            It even works with strangers. One study found that people with similar body odors are more likely to hit it off, and in a blind test even a third stranger could identify which two scents were “click friends,” clicking on first sight.
            But how do we smell them? Not your sister, father, or lover, not your baby’s fragrant head, but complete strangers? We can smell someone’s cologne in the elevator, or that body spray that clears out the subway car, but body scents are subtler and most of us don’t hug strangers, for perfectly good reasons, much less plunge our faces into random armpits. We do touch strangers, though, or get close enough to smell them, whether we realize it or not. Even in so-called low-touch cultures such as Japan and Korea, for instance, deep bows and cheek kisses bring faces inches apart. And when you shake a stranger’s hand ‒ a new team member at work, say ‒ it’s likely that soon afterward you’ll sniff your fingers.
            No way, you might say. That’s nuts. And you would share that certainty with the subjects of an experiment conducted by Idan Frumin, whose team secretly videotaped people after a handshake with someone they’d just met. A few seconds later,

            the subjects would inevitably sniff their own hands to gain some odorous information
            about the new person. “When we showed them the videos,” Frumin says, “many of the
            subjects were completely shocked and disbelieving. Some thought we had doctored the
            videos.”

            That we think we have only minimal ability or need to smell owes quite a lot to one man: Paul Broca, a 19^th century French physician and anatomist whose name you might know from Carl Sagan’s 1979 book Broca’s Brain. Broca made some seminal contributions to brain science, but he whiffed on smell. His main mistake was assuming that in the brain game, size matters. Broca noticed that our olfactory bulbs are relatively smaller than those of some “lower” animals and that our frontal lobes (specializing in speech, cognition, and free will) are relatively larger, and decided these facts must be linked. Rising from the beasts meant putting aside smell and the baser behaviors it caters to.
            There was a Freudian aspect to this since those primitive instincts were all about food and (what else) sex. As neurobiologist John McGann notes,

            Broca thought of smell as this almost dirty, animalistic thing that compelled animals to
            have sex with each other and things like that. The idea got picked up by Sigmund Freud,
            who then thought of smell as an animalistic thing that had to be left behind as a person
            grew into a rational adult. So, you had in psychology, philosophy, and anthropology all
            these different pathways to the presumption that humans didn’t have a good sense of
            smell.

            Broca’s conclusions stank partly because it isn’t the size of the bulb, it’s the brain processing it. “A bigger animal isn’t smelling a smellier world,” says McGann, and ours is a “much more complicated and powerful brain” than that of a rat or a shark. “Astonishingly,” he adds, “Broca never actually measured the sensory abilities of the creatures he discussed,” humans included. “It’s strange because… he could smell, right?”
            He could, and we can, and much better than we know. Our eyes can distinguish several million colors, our ears perhaps half a million tones, but science used to think our odor list was capped at around ten thousand. It turns out this number was just a guess by two chemical engineers in 1927. Estimates now go as high as a trillion. At any rate the things we can smell, as Harold McGee writes in Nose Dive, are “apparently endless, or at least more than we can count.”
            “I’m not crazy,” McGann says in an Atlantic article by the improbably named Amanda Onion. “There are things that dogs can do that humans can’t. But it’s also hard to generalize because we rarely test ourselves.” Alexandra Horowitz in Inside a Dog puts it this way: “Dogs bother to sniff at all. They put their noses to things. Look what we do with smell: find the Cinnabon store at the airport.” But when we do put ourselves to the test, it can be eye-opening.
            McGann studied smell in rats and mice before turning to humans, and he was unprepared for how good we were.

            We started with an experiment that required two odors that humans can’t tell apart ‒ but
            we couldn’t find any. So, we tried odors that mice can’t tell apart, and humans were like
            “No, we’ve got this.” We can detect and discriminate an extraordinary range of odors.
           
            Return for a moment to those volunteers crawling around in the grass. The authors tested fifteen substances that day, and on five of them people outperformed dogs. This doesn’t make us world champions, it simply reflects the fact that, in the words of biologist Matthias Laska, “Odors that are not relevant for you, you are usually not good at.” The scents we beat the pooches at had fruit or flower components (we’re particularly good at bananas), which are not nearly as important to a carnivore as the carbolic acids wafting from walking meat ‒ those featured in nine of the other ten trials.
            “Species specialize in different scents that are important to their lifestyles or ecological niches,” says Laska, and this goes beyond you and Rover. Pigs can’t be beat at hunting truffles, honeybees have special sugar antennae, and sharks can smell a drop of blood in ten billion drops of water. The nostrils at the end of an African elephant’s trunk can locate a water source twelve miles away. But they’d all be terrible at detecting each other’s central scents, their mates, prey, food, and friends.
            “What’s important, I think, is that nothing needs to sense everything,” says Ed Yong, author of An Immense World. “Our senses have evolved to give us exactly the kinds of information we need.” This perceptual bubble, the “thin sliver of reality we have access to,” was given the name umwelt by a German biologist in 1909. It applies to all the beings we share the planet with: blind bats following air compression waves, ticks both blind and deaf but supremely sensitive to temperature, fish guided by electrical fields, rattlesnakes by infrared. Even we humans don’t all sense the same. Androstenone, for instance, the first mammalian pheromone ever identified, smells, depending on who’s sniffing it, like sweat, urine, sandalwood, vanilla, or nothing at all.
            “If you have three people who can’t even agree on whether something is pleasant, revolting, or simply odorless,” says Gary Beauchamp of the Monell Chemical Senses Center, “you begin to see how complicated the science of smell is.”
            Umwelt might strike you as limiting or even depressing, especially when translated as “self-centered world.” One neuroscientist describes it as “unobtainable information and unimagined possibilities.” But I look at it differently. Those big brains of ours can not only sense what’s there (or some fraction of it), they can also envision what isn’t. Unimagined possibilities, in other words, don’t have to stay that way. Ed Harris, playing the producer in The Truman Show, is asked why Jim Carrey never questions his life, which everyone else in the film views as constricted and contrived. Harris shrugs: “We accept the reality of the world with which we’re presented.”
            Like Carrey’s character, though, we don’t have to. Studying other animals’ interfaces with the world, and our own, can only engender wonder at the almost infinite variety of life and our ingenious responses to it. “It’s a wonderful way to remind ourselves,” says neuroscientist Johan Lundstrom, “that there’s so much going on all the time around us that we’re mostly not aware of. We’d be driven crazy to pay attention to all of it all the time, but it’s wonderful to be nudged out of our complacency and realize that there is something amazing going on.”
            The next time life contracts, gets too fast or narrow, and you feel drab and ungifted, try petting your dog. Hug a friend. Stop and smell the chocolate.