Hundreds of years later, teeth tell the story of people who didn't get enough sunshine

Researchers at McMaster University have found a rich new record of vitamin D deficiency, one that resides in the teeth of every person and remains viable for hundreds of years or more.

The team of anthropologists has determined that looking into the microscopic structure of teeth opens a window into the lives and challenges of people who lived hundreds of years ago, and whose only record is their skeletal remains.

Their paper, published online today in the Journal of Archaeological Science, establishes that when the body is deprived of vitamin D, permanent microscopic abnormalities form in the layers of dentin, the tooth structure under the enamel, creating an ongoing record that can later be read like the rings of a tree.

"The layers store what happens as teeth grow," says author Lori D'Ortenzio, a PhD candidate in Anthropology at McMaster.

"We all know the importance of vitamin D, but until now we did not have such a clear way of measuring exactly what happened to people, and when."

The discovery is significant, since it can yield valuable information about vitamin D deficiency - also known as rickets - which continues to be a serious public health issue, affecting some 1 billion people worldwide. Most cases of rickets are caused by a lack of sun exposure, with effects that can include pain, bone deformities and failure to achieve or maintain adequate bone levels.

"If we can properly understand past changes in deficiency levels, we can evaluate where we currently are and move forward," says author Megan Brickley, a professor of Anthropology at McMaster who holds the Canada Research Chair in the Bioarchaeology of Human Disease.

Until now, scientists trying to understand historical patterns in vitamin D deficiency have had to use bones, which are problematic sources of such information. In life, bone material is constantly being remodelled, obscuring details of prior damage. After death, bones interact with soil and break down.

Dentin is not remodelled, and dental enamel - much harder than bone - protects the dentin long after death, making teeth a rich and accurate source of archaeological information.

"They're essentially fossils in your mouth," says author Bonnie Kahlon, a Lab Co-Ordinator in McMaster's Department of Anthropology.

The researchers compared the teeth of modern-day control subjects to teeth extracted from bodies buried in rural Quebec and France in the 1700s and 1800s. Their analysis showed that one Quebec man had suffered four bouts of rickets in his 24 years of life - all before he turned 13.

Examining thin sections of the teeth under a microscope and using technology at the McMaster-based Canadian Centre for Electron Microscopy, the researchers were able to show that anomalies formed in the dentin layers during years when victims failed to get enough Vitamin D to fully mineralize the structures that form dentin and bone.

McMaster University, one of four Canadian universities listed among the Top 100 universities in the world, is renowned for its innovation in both learning and discovery. It has a student population of 30,000, and more than 170,000 alumni in 137 countries.
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Reference:

Phys.org. 2016. “Hundreds of years later, teeth tell the story of people who didn't get enough sunshine”. Phys.org. Posted: July 18, 2016. Available online: http://phys.org/news/2016-07-hundreds-years-teeth-story-people.html

First Migrants to Imperial Rome ID'd by Their Teeth

Three adult men and a young adolescent of unknown gender buried in cemeteries outside Rome were likely migrants to the city, their teeth reveal.

The four immigrants all lived during the first to third centuries A.D. They are the first individuals ever to be identified as migrants to the city during the Roman Imperial era, which began around the turn of the millennium and ended in the fourth century.

This was a time when Rome was a thriving, complex metropolis, said study researcher Kristina Killgrove, a biological anthropologist at the University of West Florida.

"Up to a million people were living there," Killgrove told Live Science. "This population ebbed and flowed. You had people who were migrating in, and you had people who were dying and [people who were] migrating out."

Hidden history

Previous researchers have estimated that 40 percent of the people who lived in Rome during this period were slaves (some born locally and some imported), and about 5 percent were voluntary migrants to the city. But there was no census in Rome and no records of the comings and goings of individuals, Killgrove said.

She searched for evidence of these early travelers in two cemeteries right outside Rome's walls — Casal Bertone to the east, and Castellaccio Europarco to the south. To uncover people's origins, Killgrove and colleague Janet Montgomery of Durham University in the United Kingdom analyzed the isotopes in their molars. They focused on the first molar, which starts forming at birth and finishes forming at age 4. The enamel of this molar holds a record of what people ate and drank in their first years. 

"Teeth are kind of like little time capsules in your mouth," Killgrove said.

Isotopes are versions of the same element with different numbers of neutrons in their nuclei. The researchers analyzed strontium isotopes in molars from 105 skeletons from the two cemeteries, and further analyzed oxygen and carbon isotopes in a subset of 55 of those individuals. Strontium enters food and water by the weathering of rocks and indicates the geology of an area where a person spent his or her first years. Oxygen reflects the source of a person's drinking water, including meteorological factors like humidity and rainfall. Carbon can provide information about a person's diet, particularly whether  plants rich in the isotope C4 (maize and millet, for example) or C3 (rice and wheat, among others) were eaten.

Trading places

A combination of these isotopes revealed that two adult men who were between 35 and 50 when they died, one adult man older than 50, and a teenager between the ages of 11 and 15 almost certainly came to Rome from somewhere else. A couple of the men had high levels of certain strontium isotopes, indicative of starting life in a place where the rocks are old. Much of Italy is made of young, volcanic rocks, Killgrove said. The closest old rocks are in the Alps, or on some of the islands of the Tyrrhenian Sea. The oxygen isotope analysis also hinted that these two men could have come from an Alpine climate, though it's impossible to be sure, Killgrove and Montgomery reported.

The adolescent had low strontium isotope levels, suggestive of a home environment of young limestones or basalt. High oxygen isotopes ratios pointed to a hot climate. Those clues suggest a possible North African origin for this young person.

Four other individuals (two 7- to 12-year-olds, a male between the ages of 11 and 15 and a female between the ages of 16 and 20) also had isotope signatures that suggested they may not have been native Romans, but the datawas a bit ambiguous, Killgrove said. Figuring out if people migrated to Rome is particularly difficult because people in the city ate imported food and drank water drawn from large areas through aqueducts, meaning their isotope ratios have a broader range than people living in a more self-contained city.

It's impossible to tell why the migrants found in the Roman cemeteries moved, Killgrove said. They may have been slaves, or they may have come to Rome for voluntary reasons. The burials appear to be those of lower-class people, Killgrove said, but that doesn't mean they weren't free. Notably, the immigrants' diets do seem to have changed when they moved to Rome. As children, they ate diets higher in C4 foods, probably millet, Killgrove said.

"When they came to Rome, that becomes more in line with the Roman diet, which is more wheat-based than millet-based," she said. (Killgrove has previously found class differences in the amount of millet and wheat eaten by Romans.)

Killgrove is now working at another cemetery site outside Rome and plans more isotope analysis, along with DNA studies. An understanding of migration can deepen an understanding of Rome's development, as well as Imperial Roman slavery, acculturation to Roman culture and even disease transmission.

"It all goes back to migration," Killgrove said.
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Reference:

Pappas, Stephanie. 2016. “First Migrants to Imperial Rome ID'd by Their Teeth”. Live Science. Posted: February 10, 2016. Available online: http://www.livescience.com/53674-first-migrants-to-imperial-rome.html

Mummy Teeth Tell of Ancient Egypt's Drought

The link between drought and the rise and fall of Egypt's ancient cultures, including the pyramid builders, has long fascinated scientists and historians. Now, they're looking into an unexpected source to find connections: mummy teeth.

A chemical analysis of teeth enamel from Egyptian mummies reveals the Nile Valley grew increasingly arid from 5,500 to 1,500 B.C., the period including the growth and flourishing of ancient Egyptian civilization.

"Egyptian civilization was remarkable in its long-term stability despite a strong environmental pressure — increasing aridity — that most likely put constraints on the development of resources linked to agriculture and cattle breeding," said senior study author Christophe Lecuyer, a geochemist at the University of Lyon in France.

Many studies have linked dramatic droughts to crises near the end of the Old Kingdom (the Age of the Pyramids) in the third millennium B.C. But Lecuyer and his colleagues also found a jump in aridity before the downfall of Egypt in the 6th century B.C. during the Late Period, when it was conquered by Alexander the Great.

However, the new study can't resolve the occasional drops in annual Nile River floods or short-term droughts that often caused widespread famine and upsets in Egyptian history.

"Our database cannot identify short-term events, only long-term trends, and there is [only] one obvious major event of increasing aridity that took place before the Late Period," Lecuyer said.

The climate data comes from the teeth of Egyptian mummies from various dynasties at the Musée des Confluences de Lyon in France. Led by graduate student Alexandra Touzeau,the researchers drilled small amounts of enamel off some of the teeth and tested it for oxygen and strontium isotopes.

The mummy's teeth record the ratio of two oxygen isotopes (oxygen atoms with different numbers of neutrons) in their diet and their drinking water, which in this case is Nile River water, Lecuyer said. Shifts in the ratio of the isotopes indicate changing precipitation patterns in the region.

The isotopes can also indicate what people were eating, and the research team plans to publish additional studies of Egyptian diets through time, Lecuyer said. "The general drying trend had no negative impact on the Egyptian civilization in terms of cereal production or population," he said. "One of the studies we plan to publish soon reveals there was no diet change over this long period of about four millennia."

The Nile Valley wasn't the only part of North Africa to experience drying after 5,500 B.C. The Sahara Desert was once covered in lakes and grasslands, but switched to a drier regime between about 7,000 to 5,000 years ago, studies have shown.

The mummy teeth findings were published June 2 in the journal Earth and Planetary Science Letters.
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References:

Oskin, Becky. 2013. “Mummy Teeth Tell of Ancient Egypt's Drought”. Live Science. Posted: July 16, 2013. Available online: http://www.livescience.com/38153-egyptian-mummy-teeth-nile-climate.html

Anthropologists Discover New Research Use for Dental Plaque: Examining Diets of Ancient Peoples

While we may brush and floss tirelessly and our dentists may regularly scrape and pick at our teeth to minimize the formation of plaque known as tartar or dental calculus, anthropologists may be rejoicing at the fact that past civilizations were not so careful with their dental hygiene.

University of Nevada, Reno researchers G. Richard Scott and Simon R. Poulson discovered that very small particles of plaque removed from the teeth of ancient populations may provide good clues about their diets. Scott is chair and associate professor of anthropology in the College of Liberal Arts. Poulson is research professor of geological sciences in the Mackay School of Earth Sciences and Engineering.

Scott obtained samples of dental calculus from 58 skeletons buried in the Cathedral of Santa Maria in northern Spain dating from the 11th to 19th centuries to conduct research on the diet of this ancient population. After his first methodology met with mixed results, he decided to send five samples of dental calculus to Poulson at the University's Stable Isotope Lab, in the off chance they might contain enough carbon and nitrogen to allow them to estimate stable isotope ratios.

"It's chemistry and is pretty complex," Scott explained. "But basically, since only protein has nitrogen, the more nitrogen that is present, the more animal products were consumed as part of the diet. Carbon provides information on the types of plants consumed."

Scott said that once at the lab, the material was crushed, and then an instrument called a mass spectrometer was used to obtain stable carbon and nitrogen isotope ratios.

"It was a long shot," he said. "No one really thought there would be enough carbon and nitrogen in these tiny, 5- to 10- milligram samples to be measurable, but Dr. Poulson's work revealed there was. The lab results yielded stable carbon and nitrogen isotope ratios very similar to studies that used bone collagen, which is the typical material used for this type of analysis."

Scott explained that the common practice of using bone to conduct such research is cumbersome and expensive, requiring several acid baths to extract the collagen for analysis. The process also destroys bone, so in many instances, it isn't permitted by museum curators.

As for using hair, muscle and nails for such research, Scott said, "They are great, when you can find them. The problem is, they just don't hold up very well. They decompose too quickly. Dental calculus, for better or for worse, stays around a very long time."

Scott said that although additional work is necessary to firmly establish this new method of using dental calculus for paleodietary research, the results of this initial study indicate it holds great potential.

"This is groundbreaking work," Scott said. "It could save a lot of time and effort, and also allow for analysis when things like hair, muscle and nails are no longer available."
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References:

2012. "Anthropologists Discover New Research Use for Dental Plaque: Examining Diets of Ancient Peoples". Science Daily. Posted: May 2, 2012. Available online: http://www.sciencedaily.com/releases/2012/05/120502184838.htm