A team of researchers has found the genetic material of hepatitis B virus (HBV) in European skeletons from the Stone Age and the medieval period, The New York Times reports.

Publishing their findings in the journal eLife, researchers screened for pathogens among samples taken from the teeth of 53 excavated skeletons dating from Neolithic and medieval sites in Germany. The individuals whose remains were found lived from about 5000 BC to 1200 AD.

The investigators recovered the full hep B genomes from three samples, two of which were from about 7,000 and 5,000 years ago—the oldest HBV genomes recovered to date—and the other from the medieval period.

Compared with modern strains of the virus, the hep B strains found in the two Stone Age samples were relatively similar to each other. These samples were also similar to HBV that is found in chimpanzees and gorillas in the present day. The virus found in the medieval sample was more similar to modern human strains of hep B. Previously discovered virus samples from 16thcentury mummies were also similar to modern human strains.

It appears that the strain of the virus seen in the Stone Age samples may have gone extinct.

Together, these findings suggest that hep B has remained relatively stable over the past 500 years and that over the previous millennia, the virus may have crossed over from primates to human multiple times.

To read a press release about the study, click here.

To read the study abstract, click here.

To read the New York Times article, click here.