Posted on 02/05/2003 7:57:25 AM PST by Stand Watch Listen
In communist East Germany, the notoriously repressive secret police known as the Stasi kept a bizarre collection of "odor fingerprints." Lifted from wrong-thinking citizens who might one day need to be tracked by dog, the bits of cloth are now in jars gathering dust in a Berlin museum.But the idea behind them has been resurrected in the U.S. war on terrorism. The Defense Department wants to know if it can identify people by body odor, this time using artificial noses instead of dogs.
Sound like a snorter? It's not. Scientists already have linked a constellation of immunity genes with unique human body odor. And with electronic noses now sensitive enough to test beer, sample perfumes and uncover pollution and disease, it may be only a matter of time before an "e-nose" will be getting a whiff of terrorists, too.
"If a dog can do it, then it ought to be possible theoretically to make a device that can do it, but the practical questions are still unclear," said Gary K. Beauchamp, director of the Monell Chemical Senses Center in Philadelphia. The non-profit research institute has done much of the groundbreaking work in the theory of immunity-related odor types.
To get from today's state of the art to a working artificial bloodhound, however, scientists must fill in some pretty big holes in both research and technology.
Medical researcher Lewis Thomas first suggested a link between immunity and body smell in the mid-1970s. If dogs really could smell the unique "odorprints" of individuals, he reasoned, then immunity genes, being the most variable among humans, were the most likely candidates for influencing those prints.
Following Lewis' thinking, researchers discovered that inbred mice, which differed only by immunity genes, used urine smells to select mating partners with immune profiles that were most different from their own.
Later experiments showed that women tend to be attracted to the smell of men whose immunity genes differ most from their own.
In one such experiment, women were asked to smell boxes that each contained a man's sweaty T-shirt. The women preferred the smell of shirts from men with immunity profiles that were most different from their own. (There was one countertrend: Women who were taking birth control pills, which simulate pregnancy, tended to prefer the shirts of men with more similar immunity profiles. Pregnant mice exhibit the same exception.)
Other studies have linked body odor with the tendency to synchronize menstrual cycles found among women who live in the same household. Still other research suggests human babies have different odorprints than their mothers, even in utero. And it has been suggested that infants can uniquely identify their mothers by smell.
While it's clear that people with differing immunity genes produce different body odors, scientists still don't know how that happens. No researcher has isolated the compounds related to immunity type from all the other things that influence body smell.
And even if researchers knew exactly which compounds to look for, artificial noses aren't yet sophisticated enough to do the job.
The majority of electronic noses are used in industrial control processes, where they are programmed to reject off-smelling batches of food or wine. E-noses also have been designed to sniff out contaminated air in the space shuttle and to detect diseases, such as pneumonia, without the need to wait for lab results.
Still, Beauchamp said, "the fact of the matter is that the nose of a dog or a person is an incredibly complex system that still can't be mimicked by an electronic nose today."
That's what Alan Gelperin is trying to do. The Monell computational neuroscientist and biologist is working toward creating a nose that "works as well as the best mammalian olfaction."
He has a ways to go.
First of all, today's smell sensors are not sensitive to a very wide variety of compounds, said Daniel D. Lee, a bioengineering scientist at the University of Pennsylvania.
"We have cameras that can see outside the spectrum of the human eye and microphones that can detect a vibration a mile away, but in terms of chemical sensing, we are far away from what biology can do," Lee said.
Second, Lee said, computers just aren't as smart or flexible as dogs or humans or other biological creatures.
"If I get a brand-new scent that I've never smelled before, I can learn what that means and recognize it the next time I encounter it," he said. "Machines aren't very good at being able to adjust to new conditions."
Lee and Gelperin are collaborating on e-nose technology that solves both problems: a sort of electronic dog that could track fugitives and sniff out land mines or biological or chemical weapons.
Gelperin said he is confident that it can be done. It will just take time. But the Pentagon's Defense Advanced Research Projects Agency, which is funding the research, has the project on a tight schedule. The agency is planning to pass out some $3.2 million this year, with the expectation that a people-sniffing electronic nose will be available in the next five to six years as specific milestones are met along the way.
If the project is successful, privacy experts warn, hold onto your socks -- because it likely won't be limited to terrorists for long.
Use of DNA profiling, which was supposed to be limited to criminals, is increasingly creeping into the general population, said Chris Hoofnagle, legislative counsel at the non-profit Electronic Privacy Information Center in Washington. In the United Kingdom, for example, anyone merely suspected of a crime can be forced to give a DNA sample, a policy that has swelled police databases with the genetic codes of millions of people.
It may not amount to the Stasi's room full of jars. But as Hoofnagle put it, "If you build a technology that needs those samples, they will be collected."
To the extent that "ethnic" differences imply a different diet, this has been done many times using dogs.
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