Stinky stuff! This fits perfectly with my biased preconceptions. So here are two examples of chemistry used to analyze things you'd normally run away from.
The oldest traces of human poop have been dug out of a cave in Spain — and it's Neandertal poop. It's about 50,000 years old, and it's been reduced to a compressed, thin smear of organic compounds, so I guess it isn't actually so stinky anymore, but there was enough of it to analyze chromatographically. In case you've wondered your whole life about what Neandertal poop would look like, here you go.
Dead for 50 millennia, and what we know about this dead person is that they took a massive dump that was full of parasites. TMI.
I thought the paper was preliminary and rather general -- they don't or can't make very specific conclusions, but then, I imagine they were excited to be the first to get any discussion of Neandertal feces into the scientific literature. We do know a couple of things: Neandertals ate both their meat and their vegetables, and they had gut bacteria with similar physiological properties to our own.
Taken together, these data suggest that the Neanderthals from El Salt consumed both meat and vegetables, in agreement with recent hypotheses based on indirect evidence. Future studies in Middle Palaeolithic sites using the faecal biomarker approach will help clarify the nature, role and proportion of the plant component in the Neanderthal diet, and allow us to assess whether our results reflect occasional consumption or can be representative of their staple diet. Also, this data represents the oldest positive identification of human faecal matter, in a molecular level, using organic geochemical methods.
Besides having corroborated our method and obtained the first evidence of an omnivorous Neanderthal diet from faeces, our results also have implications regarding digestive systems and gut microbiota evolution. Approaching the evolution of the human digestive system is difficult because there is no fossil record indicating soft tissue preservation. Our results show that Neanderthals, like anatomically modern humans, have a high rate of conversion of cholesterol to coprostanol due to the presence of bacteria capable of doing so in their guts. Further research will allow us explore this issue in the context of human evolution.
I said I had two unpleasant examples of useful chemistry, and here's the second: using the characteristic odors of different stages of decay to quantify the time of death.
An international research team used two-dimensional gas chromatography time-of-flight mass spectrometry to characterise the odours that create this smell of death: volatile organic compounds (VOCs). By measuring the VOCs released from pig carcasses the team identified a cocktail of several different families of molecules, including carboxylic acids, aromatics, sulfurs, alcohols, nitro compounds, as well as aldehydes and ketones. The combination and quantities of these VOCs change as a function of time as a cadaver goes through different stages of decomposition.
I think I'm getting a sense of the difference between chemistry and biology. I prefer the bodily fluids in my subjects to be fresh, preferably spurting; chemists seem to favor observing the degradation and volatilization of fluids from dead things. Chemists may offer their repudiations of my sentiments in the comments.