Teeth track diet, lifespan, professor says

Future archaeologists probably will scratch their heads at modern teeth.

They might discover some coated in gold or inlaid with gems and stones. Remnants of other societies will include teeth that are blackened or filed into sharp fangs.

Teeth — a humble and

faithful fixture of archaeology — tell us a lot more than cultural aesthetic. They track the evolution of fundamental human traits: our diverse diets, long childhoods and expanding lifespans, Ohio State University anthropologist Debbie Guatelli-Steinberg details in her book, “What Teeth Reveal About Human Evolution.”

“Teeth preserve a record of their own,” she said. “It’s almost like a fossil already, but in your mouth.”

Because teeth have an enamel shell and are more heavily mineralized than other parts of the skeleton, they are especially resistant to destruction and decomposition by bacteria. Enamel also preserves precious information about its owner, ready for scientists to mine.

“There are a lot of clues in teeth,” Guatelli-Steinberg said.

Her book, published this past fall, stitches together decades of anthropological research on human and primate teeth. Brian Foster, an assistant professor of biosciences in OSU’s College of Dentistry, said the big picture painted by fossil tooth records is relevant for modern dentistry studies, including his own.

“Our bodies, tissues, organs and teeth are the result of millions of years of pressure to become the modern human,” Foster said. “Our teeth are still not necessarily well-matched for the present.”

Today’s diets of soft, processed and sugary foods are nothing like the huntergatherer regimen that humans ate for 99 percent of our evolutionary history, GuatelliSteinberg noted.

Researchers have used tooth enamel’s ability to absorb certain elements of our diet to map how the human diet has diversified over time.

For example, carnivorous diets are marked by a certain ratio of barium to calcium in enamel. Particular carbon types preserved in tooth fossils indicate the ingestion of different types of plants.

“You are what you eat,” said Guatelli-Steinberg.

And being able to eat a variety of food types is highly advantageous for a species, she said.

“That could have contributed to human’s evolutionary success,” she said. “When you’re more of a generalist, you have a better chance of surviving. Super-specialized animals have higher rates of extinction.”

Tooth fossil records also document how industrialization and culture have affected our bodies. The rise of agriculture, manufactured food and sugar has introduced humans to dental decay and gum disease, both of which are now common.

“Today cavities are rampant, but there are just a handful of fossils with cavities,” Guatelli-Steinberg explained. “And when we have access to dentists and orthodontists the teeth straighten out.”

Foster said that as a researcher, he was drawn to understanding the evolutionary history that preceded the modern dental problems he studies.

“When you’re a clinician you think about treating the person in front of you,” he said. “But when you’re reading about the evolutionary history of teeth, you think why? Why are our teeth not prepared for this?”

Also built into tooth structure are microscopic layers that — much like tree rings — record information about a human’s age and growth period. Using those markers, researchers can show that our ancestors matured more quickly.

Today, adult teeth don’t appear until the age of 6. But permanent molars emerged in 3 - and 4-year-old early hominids, Guatelli-Steinberg said. That’s an indication of a much shorter childhood with less time for observing and learning from caregivers.

“Your puppy is not a puppy for long — its teeth grow fast, too,” she said.

Researchers continue to study how species are related to one another by comparing the bumps and grooves of tooth fossils.

For example, scientists based their idea that Native American ancestors must have traveled from Asia to the continent across the Bering Strait because of a shared shovel-shaped incisor. Advances in DNA technology later confirmed that thesis.

In her research, GuatelliSteinberg is collaborating on a project to use Homo naledi teeth to better understand the most recently discovered early human, which made headlines in 2015.

Unlike other artifacts that fade in and out of cultural relevance or crumble under the weight of time, she said, teeth will remain integral data for archaeologists.

“Before people used DNA to understand modern human relationships, they used teeth,” Guatelli-Steinberg said. “Sometimes it’s really your only source of information. It’s an exciting window to the past.” This list is compiled from voluntary submissions by parents to hospitals. Bridgette/ boy, Jan. 17 Briana/ girl, Jan. 16 Jan. 17 Jan. 17 girl, Jan. 17

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