Scientists have found that our teeth can provide a record of human life, much like the rings of a tree.
The discovery that our teeth are an "archive of life" could allow us to better understand menopause, birth patterns and child-rearing among early humans, according to a new paper by a team of researchers from New York University.
"Our results make clear that the skeleton is not a static organ, but rather a dynamic one," study lead author Paola Cerrito, a doctoral candidate in NYU's Department of Anthropology and College of Dentistry, said in a press release.
Cerrito told CNN that the team were pleasantly surprised by the implications of their research, which they had originally designed as a way of investigating the reproductive patterns of extinct human ancestors such as Homo erectus.
"We weren't expecting these results," she said.
The so-called biological archive in our teeth shows the effect of reproduction, systemic illnesses and imprisonment on our bodies, say the study's authors, who focused their research on cementum, a kind of dental tissue that covers the roots of our teeth.
From the moment a tooth emerges from the gum, cementum starts to form annual layers, similar to a tree's rings.
"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," said co-author Timothy Bromage, a professor of at NYU's College of Dentistry.
For example, the paper shows that there will be permanent changes in the microstructure of cementum in someone who has suffered systemic illness, and this can be accurately dated.
Cerrito told CNN that the method could be used in archeology, for example to piece together information on human remains from ancient civilizations, and forensic archeology, by helping investigators to find out more details about unidentified human remains, such as those found on the U.S.-Mexico border.
The team looked at almost 50 human teeth from people with known medical history and lifestyle data, using imaging techniques to reveal cementum bands.
They then linked these bands to life stages, and discovered connections between life events and tooth formation.
"Just like tree rings, we can look at 'tooth rings': continuously growing layers of tissue on the dental root surface," Cerrito said in the press 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."
The full paper appears in the journal Scientific Reports.
Next, Cerrito and the team are working on how to differentiate life events by studying changes in levels of specific minerals, such as zinc and copper.
This will provide an even more detailed picture of the life of a tooth.
The researchers are also working with high-resolution CT scans to develop a non-destructive method of studying cementum.
This would allow them to study samples from Neanderthals and other creatures that, for conservation reasons, can't be physically cut.
