Teeth can reveal evidence of stressful lives and the menopause, study shows
Tell-tale signs of stressful life events could be found in our teeth, say researchers who have found birth, menopause and even imprisonment appear to leave their mark in tissue that is laid down throughout life.
The phenomenon is similar to the way the thickness of annual tree rings can tell us about the climate and environment in which the tree grew. In teeth, changes to the way the tissue interacts with light offer the clues.
“We didn’t know that a portion of our organism served as such faithful biological archive for the entirety of life,” said Paola Cerrito, co-author of the research from New York University.
Researchers behind the study say they believe the discovery could help shed light on a longstanding conundrum. Humans are unusual as they are one of only a few mammal species that live for many years after they stop being fertile. This trait that has led to a number of theories including the “grandmother hypothesis”, the idea that post-menopausal women survive to help their children to grow up and reproduce.
The researchers say that in order to test the theory they needed a way to look at possible evolutionary links between birth patterns and menopause, and changes in the way children are reared. The new study, they say, may do just that.
The team are now looking at the teeth of primates and human relatives such as Neanderthals to see if they show the same tell-tale clues.
However, Cerrito said the findings could also be useful in other fields. “The methods we developed can be used by archaeologists of the ancient world to piece together a more complete understanding of the lives of past civilisations 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,” she said.
Writing in the journal Scientific Reports, Cerrito and colleagues report how they analysed 47 teeth from 15 modern, deceased individuals, looking
’These methods can be used by archaeologists of the ancient world’
Paola Cerrito Co-author of the research
at a number of teeth for nine of them.
It has long been known that tooth enamel forms layers over time, but this process stops once the teeth have finished forming. As a result, Cerrito and colleagues looked at a different tissue, cementum, that grows throughout an individual’s life. This tissue covers and protects the tooth’s root, and helps connect teeth to the jaw.
Looking at the teeth using polarised light microscopy, they found the interaction of the cementum with light was not the same throughout the tissue.
Taking into account the age of the individual at death and the thickness of the cementum, the team found that these distinct changes seemed to line up with the timing of known events in the life of the individual in question, including giving birth and menopause.
“Sadly, in a number of individuals that had been imprisoned prior to death, we found evidence of that event,” said Cerrito.
The approach, at present, does have a number of limitations, including that the type of change in the cementum is the same for different life events, while even within the same individual, different teeth offer slightly different timings.