Kissing may have been deadly thousands of years ago, Scandinavian bodies reveal
As the ancient people of modern day Scandinavia fought through the Stone Ages to survive and provide for their families, they were also battling an invisible killer.
Around 6,000 years ago, the people of Sweden and Norway became less nomadic and set down roots in agricultural communities, kicking off the Neolithic period.
With this newfound stability, they suddenly faced the challenge of increasing population density and interacting with livestock — and the bacterial infections that come with both.
In a new study, published March 7 in the journal Scientific Reports, researchers analyzed the teeth of 38 Stone Age remains for the lingering DNA of deadly infections.
Teeth tell the story
Teeth, often the most well preserved part of human remains, give a unique look at the life of the person before their death, researchers said.
They collected samples of teeth from 38 bodies discovered at 11 archaeological sites across Norway and Sweden, representing many different cultures at the time, according to the study.
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Some samples, from southern Norway, were about 9,500 years old, the researchers said in a news release, while others from Sweden were closer to 4,500 years old.
Some were from hunter-gatherer communities, others farmers, and all of the teeth were “shotgun-sequenced” for DNA, the researchers said.
The researchers were on the hunt for microbial DNA, the pieces left behind after a bacteria lives in a body.
Deadly bacteria discovered
Not all bacteria is bad. In fact, you can thank bacteria for healthy digestion and for keeping the environment inside your digestive tract in shape.
Other bacteria can be deadly, and that’s exactly what the researchers found.
The researchers found five different species of pathogenic bacteria, or bacteria that would have caused a disease, ones that are potentially life-threatening.
First, the DNA of Y. pestis, the bacteria that causes the plague, was discovered in the teeth of an adult female from southern Sweden. Based on previous research, it’s the oldest case of the plague found in remains to date, the researchers said.
They also found another related species, Y. enterocolitica, which causes a “potentially lethal” infection with symptoms like diarrhea and fever, according to the study.
“The bacterium is typically spread from contaminated water and food, but there are also signs of some transmission between humans as well as (from animals to humans),” the study said.
While the plague may not be a modern problem, food poisoning is, and the researchers found DNA belonging to S. enterica, or salmonella.
“In modern populations, S. enterica is typically transmitted to humans through ingestion of contaminated meat, eggs, or milk, though (animal) transmission is also possible,” the researchers said. “Interestingly, these two individuals were recovered from the same grave and this finding could thus imply the cause of death.”
The researchers then found C. botulinum, which causes botulism and is found in decaying flesh, and C. tetani, a related bacteria that can also cause a lethal infection.
But two other infections stood out the most — meningitis and gonorrhea.
A cultural change
N. meningitidis, which causes meningitis, is passed through saliva, researchers said.
That means that while it can spread from a cough or sneeze, close proximity is necessary for the disease to spread from person to person, commonly from kissing.
That’s also the case of N. gonorrhoeae, the bacteria that causes gonorrhea, a sexually transmitted disease.
Helena Malmström, a study author and researcher at Uppsala University in Sweden, says the presence of these bacteria show the cultural change that occurred when people became less nomadic and started living in larger communities at the end of the Stone Age, according to the release.
The researchers said the shift from hunter-gatherer to farmer can be seen in the bacteria. As they moved into communities, they saw more infections from food and water, from interactions with livestock and interactions with each other.
All of these infections are relatively easy to treat with modern medicine, the researchers said, but at the time, they were likely fatal.
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