A new study suggests our teeth reveal a lot more about us than just how often we brush.
In fact, our teeth may dutifully record any experience that's made a meaningful impact in our lives, from divorce to disease to menopause to even spending time in jail.
And yes, that includes being born.
According to the study published this month in the journal Scientific Reports, all of those events are — almost literally — etched in stone.
Or, at least the hard material known as cementum that covers the root of each tooth. While it's considered a connective tissue, helping firmly root a tooth's fibers to the jawbone, cementum is very bone-like — and hardly the material one might expect to record life's experiences.
"Our results make clear that the skeleton is not a static organ, but rather a dynamic one," study lead author Paola Cerrito of New York University's Department of Anthropology and College of Dentistry notes in a press release. "We weren't expecting these results."
Indeed, cementum is as dense and rigid as you might expect for the job it performs — keeping our teeth firmly in place. Along with enamel and dentin, it's considered a hard tissue. And yet, it also manages to be a meticulous chronicler of our lives on this planet.
That may have something to do with how, over time, cementum forms layers, much like the rings of a tree. The first such layer is formed when a tooth emerges from the gumline.
Teeth: A new way of looking at history
For the study, researchers looked at 47 sets of teeth from 16 people between the ages of 25 and 69. They also had access to each individual's known medical history and personal lifestyle data.
Those teeth, as Inverse reports, hailed from a collection of skeletons of Central African Malawians. The remains were accompanied with extensive medical records and thoroughly documented personal histories.
Once the team connected the formation of each layer or band to specific life stages, they were able to trace specific life events to tooth formation.
"I had an 'ah-ha moment' when looking at the thin sections [of the cementum] under the microscope and thinking that I could try to match what I saw with data regarding the specific life events of individuals," Cerrito tells Inverse.
In fact, the biological records were so detailed, they revealed when an individual was imprisoned or afflicted with serious illness.
'Just like tree rings'
"Just like tree rings, we can look at 'tooth rings': continuously growing layers of tissue on the dental root surface," Cerrito explains in the release. "These rings are a faithful archive of an individual's physiological experiences and stressors from pregnancies and illnesses to incarcerations and menopause that all leave a distinctive permanent mark."
It's all encoded, they say, in microstructural changes to a specific layer. But so far, researchers haven't been able to discern the specific causes of those changes. One psychological event, like going through a divorce, might look a lot like contracting a disease.
In any case, the discovery could result in a star-turn for a tissue that's long flown under the radar — as reliable yet unheralded as the building material it shares its name with.
"The discovery that intimate details of a person's life are recorded in this little-studied tissue, promises to bring cementum straight into the center of many current debates concerning the evolution of human life history," study co-author Timothy Bromage, a professor at NYU's College of Dentistry, adds.