Ancient teeth trace the history of epidemics
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- Published: Monday, 17 August 2020 09:53
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Paleogenomics, which studies DNA in remnants of ancient teeth, has been looking at how humanity’s first encounter with disease is thousands of years older than originally thought. The growing evidence suggests that the first epidemics forced change onto societies. “In the case of covid-19 we see similar processes, but we are watching it unfold in real time,” said Anne Stone, professor in the School of Human Evolution and Social Change at Arizona State University.
The earliest written records of tiny infectious organisms overhauling human societies stretch back as far as the Plague of Justinian in A.D. 541, which may have killed up to 50 million people, or even the earlier Antonine Plague in A.D. 165, which left 5 million dead.
Paleogenomics has amounted to a revolution in understanding disease history, says Maria Spyrou, a microbiologist at the Max Planck Institute in Germany. “This is one of the things that we can now start saying,” said Spyrou, adding that where historical records are lacking, DNA evidence offers the possibility of filling in gaps, sometimes in surprising ways.
“One of them is plague,” Spyrou said. “Until 2015, we thought that plague was maybe a 3,000-year-old disease.” Scientists and archaeologists now believe, however, that the plague bacteria, which caused the Black Death in Europe, infected humans roughly 5,000 years ago in the Stone Age. The bacteria, after it had entered the bloodstream and likely killed the host, circulated into the pulp chamber of teeth, which kept its DNA insulated from millennia of environmental wear and tear. In the past decade, scientists have been able to extract and analyze that DNA.
“It (the Black Death) was probably was the first pandemic,” said Simon Rasmussen, a genomicist at the university and lead researcher on the plague study. In the Stone Age, also called the Neolithic period, humans made unprecedented moves to gather in large settlements with up to 10,000 people in close quarters with animals and virtually no sanitation. “It’s the textbook place of where you could have a new pathogen,” he said.
Paleogenomics has also allowed archaeologists to fill in one of the biggest silences in the archaeological record: disease. Pathogens rarely leave traces on bones, and populations without writing could die out without any readable record of the cause. With the ability to read traces of DNA preserved in teeth, historians are learning about the organisms inside ancient humans.
Kristian Kristiansen, a University of Copenhagen archaeologist and a co-author of the plague study, believes his group’s research illuminates the causes of a Stone Age demographic transformation, called the Neolithic decline, which archaeologists have long studied. Settlements at the time were disappearing faster than they were appearing, and within a few hundred years, most of the population had been replaced by migrants from the Eurasian Steppe. Researchers had only ever hypothesized that disease may have played a role in crippling the native population before it was overtaken, but now they have evidence, Kristiansen says.
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