Science in Disguise
Medicinal clays as an example of ancient science.
Back in 2014, my third book, Eureka: Discovering Your Inner Scientist was published by Basic Books. The idea of the book is to demonstrate the universality of scientific thinking by making connections between the process of science (defined very broadly) and things that non-scientists do for fun. You can get a bit of a sense of it from this promo video I did, adapting one of the chapters:
I’m still really proud of this book as a book. It covers a wide range of topics across different sciences and moments in history, and was a ton of fun to research. The general topic is something I was and am passionate about— I firmly believe that everybody is capable of thinking like a scientist, no matter how much they protest that “My brain just doesn’t work that way.”
As a commercial product, though, it was a flop. It’s far and away the worst seller of my four published books— Breakfast with Einstein, published in late 2018, passed its four-year sales total in a matter of a few months. I have no idea why it bombed so badly— I thought it was a sure thing, and busted my ass promoting it, and it even got good reviews but… nothing. The whole thing was very demoralizing.
Thanks to that book, though, I remain fascinated by evidence of ancient science (again, the general process, not the modern collection of institutions we often refer to by the term). Last week brought in a good one, via a Substack post by Anton Howes about terra sigilata, healing clay that was marketed from antiquity up into the 1800’s. While this has since been thought to be a bit of a scam, Howes notes that more recent discoveries suggest there was something there, after all:
Just last year, teams of scientists and archaeologists published analyses of various terra sigillata at the Pharmacy Museum at the University of Basel. They discovered that some of them actually had antibacterial properties after all.
The key thing was seemingly not the clay itself, but its ritual treatment. In ancient times this involved priestesses of Artemis mixing the mud with water and leaving it, before drying it out and applying the stamp; in the fifteenth and sixteenth centuries it was similarly covered with spring water and left to stagnate, or else dug at certain times of the year, only to a shallow depth, or from particular areas close to water. Thanks to recent advances in DNA-sequencing, we now know why: the ritual treatment of the clay appears to have introduced a fungus closely related to Penicillium, called Talaromyces, which produced an antibacterial and antimalarial called bioxanthracene B. It seems our ancestors who bought and used the clay were not being taken for fools after all.
(The link in that is to a paper with a more mineralogical approach but a good description of the rituals. For the discussion of fungal components, the right link is probably this one. )
This kind of thing— ancient folk remedy turns out to actually have antibacterial effects— often gets held up as an example of the power “other ways of knowing” beyond institutional Western science, but as in most such cases, I would say that this is really science in disguise. That is, it’s not hard to see how the look-think-test-tell process I discuss in the book as the core of science comes into play here, even though there’s no possible way for the people involved to understand things the way we would today. What they were doing is something much more than just “dirt from this place has healing properties” or “this religious rite turns dirt into medicine”— it’s selecting a very specific subset of clay from a specific location and preparing it in a specific way. That’s the product of centuries of trial and error, gradually homing in on something that works as well as possible.
Of course, where they end up is a local maximum, in math-y terms, because they lacked a good underlying model of why the clay works. It does what it does about as well as it can, but can’t match the results of a more directed search to isolate particular ingredients. That limit is a big part of why it fell out of favor (plus the market was diluted by people misappropriating parts of the process), and the lack of an underlying model was a big part of why it was discounted— when chemists analyzed terra sigillata in the 1800s, they didn’t have the example of penicillin to suggest the concept of something ancillary growing in the clay having beneficial effects. A better microscopic understanding of the operation of both disease and drugs opens the conceptual space to re-evaluate the older practice, and find the science that was hiding there all along.
So, as I said, it’s a cool story, and the paper with the description of the rituals is also fun to look at (the link in the quoted passage is paywalled, but if you can’t find a way around that in 2021, I don’t know what to tell you). It takes an interesting approach to the problem of explaining these historical remedies by “working backwards” from published descriptions. And of course, it was also a fun excuse to revisit a book that I remain pleased with.
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