Medieval Ashkenazi Jewish genomes more diverse than expected

Ancient DNA extracted from the loose teeth of 33 individuals who lived in 14th-century Erfurt, Germany has revealed Ashkenazi Jews were more genetically diverse in the Middle Ages than today.

In advance of a municipal construction project, archaeologists in 2013 partially excavated an ancient Jewish graveyard in Erfurt and uncovered 47 medieval graves. Five years later scientists began studying the remains – extracting 38 DNA samples from loose teeth. Researchers included an international team of over 30 experts who analysed the DNA and compared hundreds of thousands of genetic place markers against modern Ashkenazi genomes and published their results in Cell.

Study author Professor Shai Carmi, from the Hebrew University of Jerusalem, Israel, said that the medieval Jews studied 'were noticeably more genetically diverse than modern Ashkenazi Jews. An even closer inspection revealed that the Erfurt population was divided into two groups: one with more European ancestry compared to modern Ashkenazi Jews, and one with more Middle Eastern ancestry.'

Professor Carmi stated: 'Today, if you compare Ashkenazi Jews from the United States and Israel, they're very similar genetically, almost like the same population regardless of where they live.'

Ten samples were sent for radiocarbon dating, which indicated that these individuals lived between the years 1270 and 1400 CE. Dental isotopes indicated that some of the individuals were immigrants. Erfurt was a major Jewish community at this time, having been settled in the 11th century. There was a massacre of Jews in 1349, but many survivors resided in this area before being expelled in 1454.

Author Professor David Reich, professor of genetics at Harvard University, wrote: 'Jews in Europe were a religious minority that was socially segregated, and they experienced periodic persecution. Our work gives us direct insight into the structure of this community.'

Ancient Jewish DNA data is difficult to obtain because there are Jewish laws that ban the disturbance of deceased individuals. Researchers obtained approval from local rabbis in Germany to research using the detached teeth from the excavated remains.

Two small nuclear families were excavated in this group, which means that the research results are not fully indicative of the whole community at that time. However, the research provides a rare insight into Jewish history. In fact, it follows on from the recent discovery by researchers from University College London and the Natural History Museum that human remains found at a site in Norwich belonged to Jewish victims of a pogrom in the 12th century (see BioNews 1158).