No, I’m not being insulting. I smell, too. So does everyone else.
Unfortunately (or perhaps fortunately) human noses are not particularly sensitive, and so we only notice one another’s smells under certain circumstances, which we are all familiar with and I am therefore spared from having to enumerate.
But to those of the more advanced olfactory persuasion—yeah, I’m looking at you, Rover—not only do we smell, we each have a very particular smell: an odourprint, if you will, that distinguishes us from the crowd just like our fingerprints do.
There are a lot of researchers sniffing around the topic of odourprints right now, as Ivan Amato points out in a lengthy article in the October 12 issue of Chemical and Engineering News.
Down at Florida International University, for instance Kenneth G. Furton is trying to establish a scientific basis for dogs’ well-known ability to tell one person from another by smell.
For more than 2,000 years, this ability has been used in fighting crime. There’s an account from the reign of King Pyrrhus (300-272 B.C.) of two soldiers confessing to the murder of a slave after the slave’s dog later flew at them in a snarling rage.
Today, in Europe in particular but also in North America, law enforcement officials sometimes create a “scent lineup,” putting a swab containing a criminal’s scent from a crime scene in with a series of decoy scents, then watching to see if a dog previously presented with a pad swiped on a suspect pays the crime-scene sample special attention.
Not surprisingly, courts are reluctant to take the dog’s word…or snuffle…for it, and so are seeking scientific validation of this ability.
In one study, funded by the Netherlands’ National Police Agency, Furton swabbed the hands of 60 different people with specially cleaned pads, placed the pads inside glass vials, and then collected and analyzed the volatile compounds they emitted.
In all, 63 compounds were identified, “a mix of acids, alcohols, aldehydes, hydrocarbons, esters, ketones, and nitrogenous compounds,” Amato writes. And sure enough, pattern recognition could be used to identify individuals from the specific mix of those compounds.
If you could reliably identify individuals by scent using artificial sniffers, the uses would go far beyond scent lineups. For instance, you could collect odourprints from individuals in airports and train stations and match them to a database of odourprints from known or suspected terrorists. (It’s already been tried, after a fashion: the Stasi, the notorious East German secret police, used to collect odour samples from things like specially designed seat cushions, with the idea of using those odours to identify and track specific people using sniffer dogs.)
The Defense Advanced Research Projects Agency in the U.S. has already spent tens of millions of dollars on a program to create an artificial version of the canine nose with something like this in mind.
Of course, there’s an obvious challenge: our smells, or at least our obvious ones, aren’t constant. Dietary changes affect the odour of breath and urine. So can prescription drugs. And then, of course, there are shampoos, perfumes, and lotions.
Much of the work on odourprints, then, is focused on finding the chemical emissions that never change, which animals are adept at reacting to. There’s reason to believe these individual-specific odours might arise from the genes and cell-surface proteins of the immune system’s major histocompatibility complex…but after decades of searching, researchers haven’t identified them yet.
Even if we never figure out how to identify odourprints, the research along the way is paying off. The volatile chemicals given off in breath and by skin may offer new ways to diagnose diabetes, skin and lung cancer, and more. And since stress associated with lying has a physiological effect; might it be possible to literally sniff out liars in, for example, an airport security lineup?
But how do you tell if the stressed-out person is a terrorist planning to blow something up or simply one of the many white-knuckle fliers who’s always stressed before getting on an airplane?
So while there are a lot of things we might be able to do if we can identify human odourprints reliably, we’re not there yet.
When will we be? Alas, at the moment, no one nose.