Medieval and contemporary Ashkenazi Jews are genetically virtually identical, and that’s surprising
Unique DNA analysis contributes to an archaeological revolution
Unique genetic research shows that the Ashkenazi Jewish community has been a virtually closed group since the 14th century. The international and interdisciplinary Genetic Legacies project examined DNA from the teeth of dozens of medieval and contemporary members of the community from the German city of Erfurt. The conclusion: in the past six hundred years there have been hardly any changes in the gene pool.
Genetic Legacies, a project that involved the collaboration of Professor of Ancient History Leonard Rutgers, debunks an earlier hypothesis which suggests that Ashkenazi Jews from medieval Europe were descendants of the Khazars from Central Asia. It shows that this important cultural-religious group within Judaism descended from Jewish communities from the Mediterranean region, possibly southern Italy.
Moreover, the 33 medieval Ashkenazi Jews whose DNA was examined appear to be so closely related to the current community that they may be counted among their direct ancestors. A third of the population was found to be the descendants of a single ancestral mother.
A different view on Jewish history
Because the DNA of the Ashkenazi Jewish community of Medieval Erfurt turned out to be very homogenous and matches that of their present-day descendants, the replacement being no higher than 2 to 4 percent, researchers conclude that within the community, endogamy was the rule and that few people in medieval Europe converted to Judaism.
Building on earlier work, researchers calculated that the European Ashkenazi Jewish community must have been small for much of the medieval period. The project presents calculations that suggest they consisted of no more than one or two thousand individuals.
The results of this study shed new light on Jewish history as a whole. The research indicated that the societal integration of the medieval Ashkenazi Jews was very different from what we see at an earlier point in time. During the time of the Roman Empire, Jewish diaspora communities could already be found all over Europe, yet Jews were integrated into Roman society in ways that were different from the ways Jewish communities were marginalised later.
Population genetic research at Utrecht University
Genetic Legacies is led by Professors Leonard Rutgers and David Reich (Harvard Medical School). It is a collaboration of archaeologists, archaeological services, anthropologists, geneticists, computer scientists, historians, heritage specialists, ethicists, and heritage communities from all over the world.
It aims to shed a whole new light on the roots of European identity by looking at the dynamics of the migration of diasporic minorities in Europe through the prism of archaeo-genetics.
On 30 November, the first publication of Genetic Legacies, ‘Genome-wide data from medieval German Jews show that the Ashkenazi founder event pre-dated the 14th century’, appeared in open access in the scientific journal Cell.
Medically relevant information
The analysis also revealed that the Ashkenazi Jewish community faced a so-called bottle neck early in its history. Bottlenecks occur when events such as war, disease, or persecution cause a reduction in the size of the population. When this happens, such populations experience a reduction in their genetic diversity.
The examination of the bottle neck provided medically relevant information. Sixteen pathogenic variants were identified that, when present in both parents, lead to recessive diseases. These diseases still play a devastating role within the Ashkenazi Jewish community today, especially in children and women (BRCA 1).