Sunday, March 31, 2013

The smell of death

I am no chemist and I am a bit confused. A friend asked me by e-mail if I know what specifically causes the "smell of death." Since I didn't know offhand, I thought it would make an interesting blog post. My research online has ferreted out 2 scientific sources, which may or may not be at odds with one another. The BBC cites research on insects that indicates the odor of decomposition in animals (of which, of course, we are one) is a breakdown of oleic acid. But writing from the medical examiner's office specifically about human decomposition, forensic pathologist Jonathan Hayes references the breakdown of amino acids:
"In the early stages after death, cellular metabolism slows as the internal systems begin to break down. Lack of oxygen in the tissues triggers an explosive growth of bacteria, which feed on the body’s proteins, carbohydrates and fats, producing gases that cause the body to smell and to swell. In 1885, the German physician Ludwig Brieger identified two nitrogenous compounds – putrescine and cadaverine – as the chemical basis of the smell of putrefaction; there are, in fact, a host of volatile compounds involved, including substances related to butyric acid. While together these chemicals may be characteristic of putrefaction, they’re encountered in other places, giving odor variously to bodily fluids, rancid butter, bad breath and stinky cheeses."
No matter the specifics, in action and in theory organisms are instinctively wired to avoid the foul smell. The biologists testing bugs, led by David Rollo of McMaster University, researched earlier experiments:
"A search of the literature turned up a very old article by famous sociologist and ecologist E. O. Wilson. Wilson found that ants removed the dead from their nest and dumped them in a cemetery. Moreover, he identified the active signal as oleic acid. The famous story goes that Wilson found that a drop of oleic acid on a perfectly healthy ant resulted in her being carried kicking and screaming to the cemetery. Ants can't scream, but you get the picture."
Speaking of pictures, I had a hard time finding one to illustrate this post!

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