Enamel may hold the key to tracing the health history of not only modern humans but also our ancestors — a once unimaginable possibility that is now within reach thanks to a new research method that analyses proteins stored in human tooth enamel.
The study, published in the Journal of Archaeological Science, focuses on two immune proteins: immunoglobulin G, an infection-fighting antibody, and C-reactive protein, which signals inflammation in the body.
Tammy Buonasera is an assistant professor at the University of Alaska Fairbanks and lead author of the study.
“These proteins are present in tooth enamel and can be used to study the biological health, and possibly the emotional health, of past humans,” Buonasera said.
“Analysing immune proteins in enamel has never been done before, which opens the door to studying past disease and health in a much more targeted way than is currently possible.”
Research on Tooth Enamel Health
This innovative method was applied to tooth enamel from three groups: ancestral Ohlone people who lived in the San Francisco Bay area in the late 1700s and early 1800s, European settlers in the late 1800s, and contemporary military cadets.
The research team, which included representatives of local indigenous peoples, investigated immune proteins found in the enamel of these groups against a historical background.
Increased immune protein levels
They found that indigenous peoples exposed to high mortality, stress and infectious diseases had significantly elevated levels of immune proteins.
Jelmar Arkens is a professor of anthropology at the University of California, Davis, and a co-author of the study.
“We see certain individuals, particularly children, who have very high levels of immunoglobulins, which the body uses to fight disease, and C-reactive protein, which people produce when they’re stressed,” Arkens explained.
“It breaks my heart to think about all those children who have lost parents or family members to the disease and been thrown into a new cultural environment they don’t understand, and how that has affected their well-being.”
The contrast between the Ohloni and European settlers and modern-day cadets reflects the different health challenges that different groups have faced over time.
Tooth Enamel Health Record
Tooth enamel, like the rings on a tree, forms at different stages of human development and provides a timeline of a person’s health from birth to early adulthood.
Because enamel forms during specific developmental periods, from fetal life through late adolescence, researchers can pinpoint the health of an individual at different stages in their life.
This allows scientists to compile a unique health record spanning several years. Moreover, the immune proteins in tooth enamel provide more detailed information about a person’s health than the structural changes seen in bones and teeth.
Many diseases leave no visible traces in the skeleton, but proteins embedded in enamel may record responses to disease and inflammation that would otherwise go undetected.
What’s more, tooth enamel deteriorates much slower than other tissues, allowing scientists to study the health of ancient people over thousands of years.
Modern health impacts
As well as providing insight into ancient people, this new analytical method has the potential to yield important discoveries about how stress, disease and lifestyle affect modern humans.
“Without wanting to overstate the point, looking at stress and immune responses in people from the past could provide comparisons with modern lifestyles, which is especially valuable given the depth of time,” Buonasera said.
By comparing modern-day health problems with patterns observed in ancient people, researchers can better understand how the human body has adapted to changing environments and stressors over millennia.
This study is notable not only for being the first to examine serum proteins trapped in enamel, but also for its accuracy.
“We think the approach that Tammy and her team took is relevant to this and other questions in many contexts,” said Glendan Parker, an adjunct associate professor at the University of California, Davis, and one of the study’s co-authors.
“These new tools will give us even greater insight into how people lived in the past. It’s an exciting time for biological anthropology as these tools become available.”
The full study was published in the Journal of Archaeological Science.
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