Tree Rings and Tooth Rings
A New York University study has opened the door to researchers interested in anthropology and epidemiology. Just like the analysis of tree rings can show the weather cycle of wet and dry spells, a tooth can contain an index to the events that human beings go through.
The research studied the part of the tooth that covers the root. This part of the tooth called cementum, helps to anchor the tooth to the surrounding bone. It holds ligamentous fibers that hold the tooth to the bone like the straps in a trampoline. This allows tiny movements of the tooth in the bone to accommodate the pressures of chewing food.
The cementum forms new layers as time passes that are like a tree ring. Events that affect the physiology of the person such as menopause, jail time, or systemic illness, leave their mark in the cementum. Those changes can be compared and measured to correlate with timing of events in a person’s life.
The study used teeth that were sourced from a collection that had historical information about the events that that individual went through. Imaging techniques revealed small alterations in the width of successive growth rings in the cementum. One sample tooth for a woman who had two children had distinct marks in the cementum which corresponded exactly to the mothers age when she gave birth.
The surprising finding was that the physiologically important events related by the relatives of the studied individuals left a discrete mark in the cementum that could be interpreted long after. The cementum preserves a unique written history of an individual’s life experiences. This can be very useful information to a scientist looking for evidence of the geographic spread of a past epidemic. It could also be useful to see whether groups of ancient people found in the same location experiences the same events on the same timeline.
“Our results make clear that the skeleton is not a static organ, but rather a dynamic one,” explains Paola Cerrito, a doctoral candidate in NYU’s Department of Anthropology and College of Dentistry and the lead author of the paper, which appears in the journal Scientific Reports.
The paper’s other authors include Shara Bailey, a professor in NYU’s Department of Anthropology, Bin Hu, an associate research scientist at NYU’s College of Dentistry, and Timothy Bromage, a professor at NYU’s College of Dentistry.
“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,” says Bromage.