Bronze Age migrants who travelled west from the Eurasian steppe 5,000 years ago didn’t only bring their Indo-European languages but also a penchant for kissing and the strain of herpes that infects billions of people worldwide, research suggests.
For the first time, a team of scientists, led by the University of Cambridge, has sequenced ancient genomes of the HSV-1 virus that causes lip sores and infects about 3.7 million people today. Previously the oldest sample tested dated from as recently as 1925, in a New Yorker.
The team hunted down herpes in the remains of four individuals who lived over a thousand-year period and extracted viral DNA from the roots of their teeth. Herpes often flares up with mouth infections and at least two of the people had gum disease and a third smoked tobacco.
The oldest sample came from an adult male from the Russian Urals, dating from the late Iron Age about 1,500 years ago. Two more samples were from Cambridge: one from a female buried in a 6th-7th-century Anglo-Saxon cemetery; the other from man who died in the late 14th century and was buried in the grounds of the city’s charitable hospital.
The final sample came from a young man excavated in Holland — a devoted clay pipe smoker who was probably killed in a French attack on his village by the banks of the Rhine in 1672. In combination with modern samples, the historic samples enabled the researchers to draw inferences about the progress of the virus much further back, in prehistory.
“By comparing ancient DNA with herpes samples from the 20th century, we were able to analyse the differences and estimate a mutation rate, and consequently a timeline for virus evolution,” said Dr Meriam Guellil, joint lead author, from Tartu University’s Institute of Genomics.
Her co-author Dr Christiana Scheib, Research Fellow at Cambridge’s St. John’s College, added: “Every primate species has a form of herpes, so we assume it has been with us since our own species left Africa. However, something happened around five thousand years ago that allowed one strain of herpes to overtake all others, possibly an increase in transmissions, which could have been linked to kissing.”
In their paper, in Science Advances, the authors suggest that this “something” could by the expansion of people from the Pontic-Caspian steppe north of the Black Sea. These people, known as the Yamnaya, were pastoralists and skilled horsemen who left a profound genetic, linguistic and cultural legacy across Europe and parts of Asia. The extent to which they were genocidal invaders or passed on their legacy through more positive exchange remains disputed.
The researchers wrote: “Research has shown that there were migration(s) from the Eastern European steppe region into the rest of Europe and likely an increase in population density during the Bronze Age.
“something happened around five thousand years ago that allowed one strain of herpes to overtake all others”Dr Christiana Scheib
“The primary mode of HSV-1 transmission is vertical, from parent to child; however, the addition of lateral transmission as population density increased during the Bronze Age, potentially linked to the introduction of new cultural practices such as the advent of sexual-romantic kissing, may have contributed to a shift in the dominant lineages, which have continued to circulate to this day.”
They point out that the earliest known record of kissing is in Bronze Age stories from South Asia where Yamnaya descendants had also settled. They suggest that the custom — far from universal in human cultures — may have travelled westward with the migrations into Europe from Eurasia.
About two-thirds of the global population under the age of 50 now carry HSV-1, according to the World Health Organisation. For most, the occasional resulting lip sores are merely uncomfortable, but in combination with other ailments or complications the virus can be fatal. In 2018, two women died of HSV-1 infection in the UK following Caesarean births.
The team would like to trace the disease even deeper through time, to investigate its infection of early hominins. “Neanderthal herpes is my next mountain to climb,” said Scheib.