New research suggests a tooth material called cementum can provide an archive of the entirety of the adult lifespan.
The materials that form teeth build in layers, like tree rings. As new layers form, evidence of a person's diet and lifestyle become trapped -- evidence that can later be analyzed by researchers.
Until now, scientists have relied on enamel and dentine to investigate how early human populations lived -- when they first started consuming dairy, for example. But enamel and dentine have their limits.
"Enamel and dentine are able to inform only about the period during which the teeth are developing, into late adolescence," lead study author Paola Cerrito, a doctoral candidate in anthropology at New York University, told UPI in an email. "I had the idea to pick cementum because of the potential for illuminating life history events throughout life from the time of a tooth's eruption till death. I basically shifted the time frame of the individual's life that we can look into."
From the time the tooth comes into the mouth, layers of cementum form. For the study, Cerrito and his colleagues analyzed the cementum layers from 50 human teeth. The teeth were sourced from a skeletal collection, complete with medical history and lifestyle data on collection donors. The analyzed teeth belonged to adults aged 25 to 69.
Scientists used advanced imaging techniques to highlight different cementum rings and link changes in microstructures and patterning of cementum fibers with various life events. Researchers were able to identify the signs of childbearing, menopause and other physiological stressors among the cementum layers.
"We didn't know that a portion of our organism served as such faithful biological archive for the entirety of life," Cerrito said.
The new research -- published Wednesday in the journal Scientific Reports -- builds on a growing appreciation for the human organism as a whole-body system, with the signatures of changes in health and biology recorded in the layers of disparate pieces of bone.
"As whole-organism biologists, we understand ever more how impossible it is to isolate a part of the system and try to understand it by looking at it by itself," Cerrito said. "If this, on the one hand, poses challenges in terms of the complexity of the research we endeavor to carry out, on the other it opens the discipline of human evolution to many fascinating discoveries."
According to Cerrito, the new cementum analysis techniques could be used investigate how human reproductive patterns have evolved. Cementum analysis could also help archaeologists gain new insights into ancient life.
"The methods we developed can be used by archeologists of the ancient world to piece together a more complete understanding of the lives of past civilizations by integrating written records of a person's social and public life to biological data regarding intimate details such as fertility, menopause, or other physiological stressors," Cerrito said.
Cerrito hopes his research will also help forensic scientists match deceased bodies with individual identities. And because the analysis techniques are applicable to other toothed animals, not just humans, Cerrito suggests the work can help conservationists better predict the effects of environmental stressors on animal populations.
"A challenge in conservation ecology is predicting a population's response to stressors. Making such predictions is incredibly hard as there is little knowledge of past on which to base them," Cerrito said. "The implementation of this method would permit the reconstruction of fertility patterns within an animal population known to have been subject, for example, to a past anthropogenic stressors."
In followup studies, researchers hope to expand their understanding of the effects of physiological stressors on cementum. So far, scientists have only studied structural changes in cementum, but researchers plan to tease out the effects of life changes on the distribution of elements such as zinc and copper in the dental layers.
"In such a way we will build an event-specific library of changes in ratios of elemental distribution, as each stressful event stressed the organism in its own way and determines an own change in mineral balance," Cerrito.