Friday Weird Science: Stop and smell the s**t

Apr 26 2013 Published by under Friday Weird Science

These days, we've got an infinite variety of ways to tell people what we ate for breakfast. Twitter, Facebook, Blogs, phone calls, singing telegrams!

(Believe me, what we are about to discus would be about as well received)

But you know, if you want people to really UNDERSTAND your diet, your current obsession with greek yogurt or whole grains, they need to really know the ins and...outs of the process. So if you really want people to know what you ate for breakfast, you don't need a singing telegram. You need a fecal odorgram.

Moore et al. "Fecal Odorgrams: A method of partial reconstruction of ancient and modern diets" Digestive diseases and sciences, 1984.


Really, this isn't just about subjecting your poor friends to your bodily excretions (though if you did, you'd soon have very few friends). Instead, this is about coprolites.

Coprolites are, frankly, fossilized crap. And there's quite a bit of it around from humans, usually in dry, protected environments like caves. After all, a human only leaves behind one skeleton in their lifetime, you only grow one skull. But you POOP a lot more.

And this is good because analyzing some old poop can help us understand what our ancestors ate (ah, the glamorous origins of the paleo diet). Usually this is done by things like pollen analysis and the analysis of the undigested...things in the coprolite. But what if you could do it another way?

It turns out that human poo is some really durable stuff. So much so that even poop that has been dried out and stored in a cave for thousands of years can still be pretty potent! All you have to do is add back the water, and you suddenly realize that old poop has a lot of...pep to it.

And so the authors of this study wanted to see if they could use some of the delicate lingering aromas of the poop to figure out what the ancient humans were eating. They also wanted to see how specific the odors were to different diets and species.

And this means that one BRAVE SOUL, oh verily he did suffer for science. They took stool samples from a coprolite and reconstituted it in water. This was compared to samples from: a bison, a deer, a cougar, and a bear (apparently this was the easiest s**t to get from the local zoo). It was also compared to the feces from a single man who had been maintained on a different diet for 7 days, with poop collected each day.

Each of these samples was giving off odors, and these odors were collected in a syringe (full of the local air) in the "headspace" around the poop. This was then run through a high performance liquid chromatograph, which separated out all the chemicals in the sample into peaks. Usually then the sample goes to waste, but this time? Each peak came out at the other end into the nose of a dedicated sniffer, who then let the scientists know what he smelled. I can't help picturing a long series of tubes, Dr. Seuss style, with an old man sniffing carefully at one end.

What did they get? A particularly perfumed picture of poop. First off, it turns out that human poop smells worse than bear, cougar, bison, or deer.

poop odors3

Secondly, some of the components of the diet of a person could be told by the smell. If the dude ate a peanut, the sniffer smelled the peanut. Corn and bread smelled like corn and bread. Peaches smelled like peaches, etc. In fact, the most insane thing about this study was WHAT they had their test pooper EATING. Observe:

(Table 1, Moore et al, 1984)

In the free range human, you can see a lot of coffee, many donuts, some whiskey, and more donuts, leading me to hypothesize that this test pooper was either a scientist, or possibly a policeman.

But then they switch his diet up. And not like 'on this day you're eating nothing but protein and on this day you are eating carbs'. It started out that way, but quickly went off the rails. High fiber I understand, but a whole day eating nothing but PEACHES (with a small shot of tequila in there I notice, gotta get them down somehow)?! WHY?!

Some of the odors correlated. But many of them didn't. Why did the sniffer smell mint, for example? And why DIDN'T they smell they coffee?

And the animals were even weirder
(Table 2, Moore et al, 1984)

For the animal samples, some was good. Bison poop smelled like grass, because bison eat grass. Deer smelled like grass with fruits and vegetables, because that's what they ate. But the carnivores?! ALSO smelled like grass. And corn, and leaves, and mint. When they don't eat any of those things (well, I wouldn't put it past the bear, but the cougar's an obligate carnivore and would know better).

So it makes you wonder what "smells like grass" really means for a poop sample. Is it grass? Or did the pooper in question eat turkey? In the coprolites, for examples, the sniffer detecting things like licorice. What does that mean? Is it a chemical breakdown product of something else? Or were ancient humans walking around with licorice? It's definitely possible that the ancient humans ate licorice, but the sniffer smelled it in the modern human as well, who was eating no licorice.

But if you could find out exactly which smells went along with which food components, you might get a really good picture of what ancient humans ate. But me? I'll leave that to the scientists. And the next time someone is oversharing their cereal consumption on Facebook, remember, it could be worse. It could be a fecal odorgram.

Today's Friday Weird Science comes to use via Mary Roach's new book "Gulp: Adventures on the Alimentary Canal". It's a gas of a read that will have you ruminating long after you've fully digested the content. 🙂

4 responses so far

Leave a Reply