This month the Department of Homeland Security announced plans to study the potential of body odor as a means of identifying criminals and figuring out when they're lying. The work will expand on basic research into the chemistry of the so-called human "odorprint," which scientists say is as distinct as DNA. At first whiff, the notion that individual B.O. is as special as a snowflake sounds like a rotten joke. But body odor has proved its value as a biometric for seven centuries, ever since man first started hunting bad guys with the original B.O. detector: the bloodhound.
While dogs certainly deserve a long scratch behind the ears for clueing us in to the odorprint, their days as our elite odor gumshoes may be numbered. (Canines are not as reliable as we once thought: Although the best can match scents with 85 percent accuracy, poorly trained or feeble-nosed dogs may do no better than chance.) Now scientists are figuring out their own, more accurate ways to scrutinize an odorprint. Research on electronic noses may also reveal secrets about how humans recognize each other by B.O. We know, for example, that mothers can pick out their babies by smell, and babies their mothers. Scientists call this the "armpit effect" and suspect that many other animals recognize kin by comparing body odors. This got me wondering: Could the techniques of modern B.O. analysis be used like DNA testing to reconstruct family relationships from drops of sweat? Could this analysis work on my own family? I asked one of the top researchers in the field of criminal odorprinting to help me find out.
Florida International University chemist Kenneth Furton studies the smells that might be of greatest use in a crime investigation. These, he says, are the ones that come from the hands. (Murderers rarely wield weapons in their underarms.) For the last five years, Furton has been cataloging the many chemicals that compose hand scent, including odoriferous acids, alcohols, aldehydes, hydrocarbons, esters, ketones, and nitrogen-containing compounds.
It's a rich brew, but hardly the rankest in the human odor-sphere. Hands don't contain apocrine glands, the funky B.O. factories that reside in the armpit and groin and broadcast sexual status updates. But they do have tons of eccrine sweat glands, used for thermoregulation, and oil-producing sebaceous glands, which generate their own odor signatures. These aromas mix with volatiles from our dead skin cells and exhaled breath before wafting in a plume of body heat.
I challenged Furton to construct my family tree based only on data from our sweaty hands. He had never attempted such an analysis before and made no claim that it would be possible. Yet he agreed to give it a shot. I dragooned my mother, father, Uncle Merritt, and identical-twin first cousins Ricky and Johnny into the experiment.
Odor collection proceeded according to protocol in a pair of secure, television-equipped locations. In Virginia, my mother, father, and I meticulously washed our hands without soap and then waved them around until dry. Next, we rubbed our hands to lather them up with sweat and then clasped them around a piece of gauze. For 10 minutes, we held our hands before us, as if in prayer, while our B.O. impregnated the cloth and we watched Rachel Maddow. I am told that during odor collection in California, my uncle and cousins took in a crappy Golden State Warriors game. Three scent samples were obtained from each person and then shipped to Furton's grad student Davia Hudson in Florida, who ran them through a gas chromatograph and mass spectrometer. (Click here for a dendrogram of the data.)
The results were intriguing, though hardly Nobel-worthy. Hudson said our odor profiles were "very similar" but that there was "low reproducibility" among the samples collected from each individual, likely due to contamination. So she discarded one outlier from each subject. Even still, one of the "good" samples collected from my mother came up 94 percent similar to one from her nephew Johnny, which didn't make much sense. The two of them were closer in scent than Johnny and his identical-twin brother Ricky. (Twins should smell alike.)
Still, to my eyes the family odor tree that emerged smelled like home. According to the data, I shared my dad's aroma, with similar ratios of citrus and tallow that surely reflected our shared heritage chomping pork-rib sandwiches. The clones, Ricky and Johnny, were quite alike but for a burnt note that lingered around Ricky, perhaps a side effect of his weakness for Caramel Frappuccinos. In general, the males had similar odor profiles, with the exception of my uncle, who seemed to come from another B.O. planet. He excreted the rudest bouquet—subtly oily, pungent, and sweet—which jibed with behavioral data from the dinner table. The only person who showed a hint of similarity with him—in one sample—was his sister, my mother, who is, after all, more like him than she'd like to admit. (Click here for a chemical breakdown.)
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