This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
*sings*
There was a young student who swallowed a shrew.
Didn't even chew, just swallowed a shrew.
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It's what scientists do.
(based on this)
This is one of those fantastic little snippets of science that leaves you in awe (if you can call it that) of the people who did the deeds. People have put their fingers directly in other people's stomachs for science (through a hole). People have masturbated for science, peed in an fMRI for science, and There are people out there, and I have now met one of them, who have sorted through fresh, and aged, human POOP for science (I shook this guy's hand before I knew that. I mean, I assume he wore gloves, but... *shudder*). This same person may, or may not, have swallowed a whole shrew. For science. I begged him to tell me who on the paper (or off the paper, perhaps they had a volunteer?) swallowed the shrew. He is astonishingly silent on the subject.
Crandall and Stahl. "Human Digestive Effects on a Micromammalian Skeleton" Journal of Archeological Science, 1995.
(This poor guy had no idea what was coming. Source)
Now you might think that someone who swallowed a shrew for science and analyzed what came out might be on something of a science lark. You know, just random "hey, who knows what happens if you eat a shrew?" Like the guy who analyzed his beard shavings in proximity to his girlfriend or the guy who shaved his stomach to measure his belly button lint.
But in fact there is a method to this scientific madness. And it's an anthropological method.
Scientists spend a lot of time trying to figure out how ancient peoples lived. Often, in the times before written records or buildings, or anything else, all we have to go on is bones. Usually human skeletons. But sometimes, there are other skeletons associated with the human skeletons we find. If the skeletons are of, say, fish, or domesticated animals, we may conclude that they were eaten by the humans (before the humans themselves became skeletons, anyway). But what if they are the bones of...mice? Or voles? Or rats?
Did ancient humans eat these small, presumably untasty specimens? Or were these just animals that wandered in and died in the same spot as the humans? It's difficult to tell. In some cases, such as the southwestern US, there are human coprolites (fossilized human poop) with small mammal bones in it. So yeah, they were definitely eating mice (or the local equivalent). But most environments do not result in fossilized poo (I don't know about you, but I'm a little relieved to know this). So in those cases, well, how do you know?
What you need is a digestive signature, what scientists call a "predatory signature". Different animals digest in slightly different ways, and the bones that come out the other end will therefore be slightly different. There are predatory signatures for hawks, owls, or lions, which allow scientists to analyze the bones for things like evidence of enzyme action, to show what animal ate it.
But what about humans? There has been a predatory signal for humans established for foods like fish (if the fish is found in a cave with a human skeleton, with no evidence its ever been underwater, you can probably conclude the fish was dinner), but not for things like small mammals. So. You need a digestive signature for a small mammal.
Guess it's time to have shrews for dinner!
The authors trapped some shrews, skinned and eviscerated one, parboiled it, broke it in quarters...and someone (we may never know WHO), gulped it down. I have been informed by first author Brian Crandall that the taste was reported as being "kind of like chicken," and that some tomato sauce was added to ease digestion (I asked whether it was ketchup, and he was vehement that it was tomato sauce). Before and after the shrew, the subject ingested "marker foods," foods that go through the digestive tract somewhat...obviously...and so will tell you when to expect the shrew. The before marker was corn, and the after was sesame seeds, both of which will turn up pretty obviously (if this comes as a surprise...take a look after the next corn on the cob).
Poop was collected for the next three days (I hope they got somebody regular), though most of it came through in the first two days. Each time, it was swirled in water until it was...fully dissolved (this probably took some time, as Crandall, who had to do the swirling, told me the specimens were "brain coral like", which I estimated to be what corresponds to a 2-3 on the Bristol Stool Scale). They then drained the specimens through 4 layers of cheesecloth to get out the other stuff (whatever that might be), and examined the results for bone remains. The bone remains were then coated in gold (precious poop indeed) for examination under a scanned electron microscope.
The results? Well, they got some of the bigger pieces of the skeleton "back", as it were, but in general, they had low bone survival, about 20% of the total skeleton. This means that there was heavy digestive damage, our systems can do a number on bones! This puts us with other "category 4" predators, like foxes and eagle owls.
(Figure 3, an electron micrograph of surviving jawbone with teeth)
Many of the surviving bones and teeth showed evidence of pitting and partial digestion, and the fact that so many bones were completely gone suggests that we might be able to break them down entirely! The results are interesting and potentially useful news for people who study human bones. If you find a shrew set in there...well a closer look could tell you whether that was part of dinner at some point.
But in the end, what we can really conclude from this study is that someone swallowed a shrew. Basically whole. For science. And someone analyzed what came out the other end. Deserving of an IgNobel, indeed!
Note: Brian Crandall, the first author on this paper, now works as a science educator with Mad Science, a group that inspires science learning with after school programs and stuff in grades K-8. It seems like a great group! And it's nice to know that his love of science has carried him so far.