Why Archaeologists Don’t Want You to Floss

Dirty Science by Dr Brenna Hassett

Archaeologists don’t want you to floss, (…but you probably should, anyway).

It is increasingly hard, as an archaeologist, to convince anyone you are an archaeologist. In the public imagination, there are sartorial requirements (whips, twin thigh-holstered 9mm pistols) that are simply untenable in the field, or indeed in airport security on the way to the field. Worse yet, modern archaeologists fall down on expectations extending even beyond hat choice: many of us spend our days working in perfectly nice laboratories, and almost[1] never have to escape from lava pits, crashing boulders, or high-stakes poker games in Siberia. And one of those things we do in our laboratories?

Hats are an important part of archaeology.

We judge dead people on how they brushed their teeth.

Yes, that’s correct. There is an entire science of Things Stuck In Your Teeth. It’s actually an incredibly interesting branch of dental anthropology, which is a real degree that you can have. Dental anthropology does exactly what it says on the box: it’s the study of human (and hominid, and primate…) teeth. So, what can dead people’s teeth brushing habits tell us?

For one thing, we have not always been a species of careful brushers and flossers. The invention of modern tooth hygiene goes back further than you’d think, but for the most part, humans have always eaten what they’ve eaten, and then managed to get it stuck in their teeth. It’s particularly easy to get things stuck in your teeth when you don’t clean them, because teeth get a plaque build-up over time.

Plaque, for all you good brushers out there who wouldn’t recognise it if it bit you, is the kind of pasty film that sticks to your teeth around the gum line and in the spaces between teeth. Areas of plaque are essentially little space colonies, except the colonists are yeasts, protozoa, bacteria and viruses. You feed and nurture your little gardens of Streptococcus and Actinomyces every time you eat, and the thing they like best? Sugars. The more sugars, the more they grow, and the longer they cling on, the better the chance that the chemical swamp that is your mouth will start to harden them until you have basically rock-solid bacteria graveyards stuck to your teeth. That’s biology, or, more specifically, that’s dental calculus.

Dental calculus is the mineralised build-up of plaque. Photo Credit: Camilla Speller.

It’s not pretty.

But it IS useful! Because deep within those calculus (aka tartar) deposits are little archaeological treasures just waiting to be discovered. Dental anthropologists have recovered bits of ancient food debris, snags of animal or plant material used to make twine, and even  proteins and chemical compounds left behind by different ways of cooking. It may seem like very small potatoes indeed, but finding out what our ancestors put in their mouths can actually fundamentally change our ideas of the past. Headlines were made a few years back when researchers found evidence trapped in dental calculus of Neanderthals cooking and consuming chamomile and bitter roots. Neither of those has much value as food, leading researchers to suggest that our big-browed cousins had mastered basic medicine. Others argued that there are many ways to get chamomile stuck in your teeth, and they don’t all pre-suppose the existence of Neanderthal ceramics with ‘Keep Calm and Quietly Go Extinct’ on. 

One of the most charming archaeological stories of 2019 shows exactly how dedicated study of ancient teeth can bring an entire life into vivid detail after hundreds of years. Imagine the consternation when a team from Germany’s prestigious Max Planck Institute found blue dental calculus under the microscope, in the teeth of a middle-aged woman who had been buried in a German monastic cemetery nearly a thousand years ago. A little lateral thinking and a lot of science later, and the color was revealed as lapis lazuli, a pretty but expensive stone from Afghanistan that was ground up into ink for medieval scribes to decorate manuscripts with. She had held in her teeth a history of her life as a scribe and illustrator, and a habit of sucking her brush to a point when it was dipped in exotic ink written in miniature and in ultramarine.

Lapis lazuli fragments trapped in the scribe’s calculus. Credit: C. Warinner (A); M. Tromp and A. Radini (B to I).

So, if you want future archaeologists to come and reconstruct your life, remember kids:

Don’t floss.[2]

[1] It’s the almost that gets you.

[2] You should really floss.

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Dr Brenna Hassett is an archaeologist specialising in the analysis of human remains as a researcher at University College London and a Scientific Associate at the Natural History Museum London. She has dug on sites across the globe, from Greece to Egypt to Thailand and beyond. Several of these sites but none of her boots survived the experience. She is one quarter of The Trowelblazers group and her first book, Built on Bones, was published by Bloomsbury in 2017. She is on Twitter at @brennawalks

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