Biology Reference
In-Depth Information
atory, along with one or two others, found tantalizing evidence that compounds we swallow
or inhale—from fluorinated water to asthma inhalants—may play a role in our unique smell
after death. It's not much of a stretch to think that our decaying bodies might whisper more
than a hint of je ne sais quoi of chemical compounds we've steeped our bodies in during our
lifetimes.
“We take in a lot more chemicals than we should,” Arpad said. The unanswered question
is whether those translate to volatile compounds significant to the dog, even though the car-
cinogenic compound carbon tetrachloride seems to jump out when Arpad takes air measure-
ments of human decomposition.
We have a fair amount of evidence that dogs do fine at detecting remains that are hundreds
of years old—long before fluorocarbons and freons and fluorinated compounds and solvents
and poisonous cleaners and antibiotics came on the scene. In rural areas where water isn't
fluorinated, dogs can find people who have mostly drunk well water all their lives. Domestic-
ated pets ingest plenty of fluorinated city water and chemicals, and well-trained dogs don't
alert on their remains.
Arpad believes they are getting close to knowing what dogs find important and unique
about human remains. The chemical portrait gets blurrier with buried bodies, which may
be emitting different volatiles than surface ones. He thinks he knows what volatiles dogs are
alerting on in burials—perhaps as few as thirty compounds—but he's not yet tested the the-
ory. Those volatile gases have to be available at the soil surface for the dog's nose to collect.
Even bone has twelve detectable volatile compounds.
It is possible that a unique volatile compound—something that barely registers on the gas
chromatographs positioned around bodies in Arpad and his colleagues' experimental research
plots—hits the dog's nose and lights up her brain like a pinball machine. Or it could be a few
compounds, or a bunch of them in various delightful combinations. When you combine the
variety of conditions under which dogs find human remains, from freshly deceased to hun-
dreds of years old, the options become dizzying. For instance, Arpad notes, the odor profile
for a body that has all the busy microbes associated with the digestive system working over-
time is very different from the profile for scattered limbs.
While we don't know the exact compounds they are smelling, dogs find human remains.
That should count for something. Just because dogs find the dead without an utterly coherent
scientific theory as to why, and without an easy way to test it under controls, doesn't mean
it's not happening.
Cadaver dogs' ability to find human remains may be analogous to humans' ability to re-
cognize faces. Researchers don't have a clear understanding of how facial recognition works,
but people do it effortlessly, at all angles, even in bad light. Trying to break that recognition
