Tooth enamel holds a record of human health

Enamel may hold the key to tracing the health narratives of not just present-day humans but also our ancestors. This once-unimaginable possibility is now within reach, thanks to an exciting new research method that analyzes proteins preserved in human tooth enamel.

Published in the Journal of Archaeological Science, the study 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 the study’s lead author.

“These proteins are present in tooth enamel, and they are something we can use to study the biological and potentially the emotional health of past human populations,” said Buonasera.

“Analysis of immune proteins in enamel has not been done before, and this opens the door to studying disease and health in the past in a more targeted way than we can today.”

Tooth enamel health study

The innovative method was applied to tooth enamel from three groups: ancestral Ohlone people from the late 1700s and early 1800s in the San Francisco Bay Area, European settlers from the late 1800s, and modern-day military cadets.

The research team, including representatives from local Indigenous tribes, examined the immune proteins found in the enamel of these populations, comparing them against their historical contexts.

Elevated levels of immune proteins

The results revealed that the Indigenous population, exposed to high mortality rates, stress, and infectious diseases, had significantly elevated levels of the immune proteins.

Jelmer Eerkens is an anthropology professor at UC Davis and a co-author of the study.

“We see certain individuals, especially children, with very high levels of immunoglobulins, which the body uses to battle disease, and C-reactive protein, which people produce when they are under stress,” explained Eerkens.

“It’s heartbreaking to think about children who may have lost their parents and family to disease, were thrown into a new cultural environment they didn’t understand, and how it affected their well-being.”

The contrast between the Ohlone group and the European settlers or modern cadets reflected the varying health challenges faced by different populations across time.

Health records in tooth enamel

Tooth enamel forms over different stages of human development, much like tree rings, and provides a timeline of a person’s health from birth to early adulthood.

Since enamel forms during specific developmental periods – from in utero through late adolescence – researchers can pinpoint the health status during different phases of an individual’s life.

This allows scientists to piece together a unique health record that spans several years. Additionally, immune proteins within tooth enamel offer more detailed information about a person’s health than structural changes observed in bones or teeth.

Many illnesses don’t leave a visible trace on the skeleton, but the proteins embedded in enamel may record responses to illness or inflammation that would otherwise go undetected.

Furthermore, tooth enamel degrades much more slowly than other tissues, allowing scientists to investigate the health of ancient humans over thousands of years.

Implications for modern health

Beyond gaining insight into ancient populations, the new method of analysis has the potential to provide critical discoveries about how stress, disease, and lifestyle impact modern humans.

“Without trying to overstate things too much, looking at stresses and immune responses in past populations could provide points of comparison with modern lifestyles that can be especially valuable because you have that depth of time,” said Buonasera.

By comparing modern health issues with patterns observed in ancient populations, researchers could gain a better understanding of how human bodies have adapted to changing environments and stressors over millennia.

In addition to being the first to examine serum proteins trapped in enamel, the study’s precision is noteworthy.

“We see the approach Tammy and her team have taken to be relevant in many contexts, for this and other questions,” said Glendon Parker, adjunct associate professor at UC Davis and one of the study’s co-authors.

“These new tools will give us further insight into the lives of past peoples. It is an exciting time for bio-anthropology as these tools become available.”

The full study was published in the journal Journal of Archaeological Science.

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