Genetic study confirms history of the Druze community

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Druze sheikh of a village in the mountains near Beit-Eddine, Lebanon. Image: Public Domain

According to a genetic study the Druze community began to form genetically in the 11th century AD, and there has since been no genetic impact of other ethnic groups.

This is the first genetic study to discover that the Druze community has genetic origins in the 11th century AD,” said Professor Atzmon of the University of Haifa’s Department of Human Biology and Department of Medicine and Genetics. This genetic finding correlates with the Druze community’s beliefs regarding their origin.

Traditionally, the Druze people believe that their community was founded in the 11th century AD as a new religious movement under the sixth caliph of the Fatimid Dynasty of Egypt. There are currently 1.5 million Druze around the world, residing mainly in Syria and Lebanon, with the remainder in Israel and Jordan. According to Druze tradition, marriages take place only within their community.

An international team of researchers was formed to carry out this current study, published in the European Journal of Human Genetics — Nature, which sought to examine whether the Druze  people of today have a similar gene pool and if so, when that gene pool began to take shape.

Family history

The study included 120 participants from forty families. Twenty families were from the village of Beit Jan located in the Upper Galilee and twenty were from Majdal Shams, in the Golan Heights. The families were selected according to the origins of their extended families (clans), based on their family names and on information that was passed down orally from generation to generation. The mother, father and son of each family were genetically tested. All the families who participated in the study were from different clans so that the sample would be representative and it excluded first- or second-degree family relationships to any other participants in the study. These characteristics all significantly increased the study’s genetic accuracy. “In this study, we incorporated data that was published on the Druze of Lebanon, the Carmel Mountain region and various other populations in order to test the genetic structure of the Druze population relative to other populations,” said Prof. Zidan, director of the oncology department at Ziv Medical Centre and Faculty of Medicine at Bar-Ilan University

The results indicated that the Druze do indeed share a high genetic similarity that significantly distinguishes them from member of other groups and communities in the Middle East. When the researchers went back in time to discover when this genetic similarity began, they reached the 11th century AD, about 22-47 generations ago (there are differences of opinion over the duration of a generation). During this period a genetic “bottleneck” was formed, i.e., the genetic origin of many descendants came to an end, the community’s population decreased and the individuals in the population became more alike genetically. According to Prof. Atzmon, their research findings limit the ancestors of the Druze community to several hundred families, who founded the community in the 11th century AD.

Marriage within clan

The researchers also found that there is no evidence of new genes entering the Druze gene pool over the last 1,000 years. In other words, no additional groups from the outside joined this community. In addition, the researchers found evidence of genetic differences between Druze populations from different regions: Lebanon, the Golan Hights, the Upper Galilee and the Carmel Mountain. This strengthens the evidence that marriages take place only within each clan.

When they went further back in time, the researchers discovered another interesting finding. It came to light that, 500 years prior to the beginning of the Druze religion, around the 6th century AD and at the time of the birth of Islam, a genetic group began to take shape that formed the basis of the Druze community’s ancestors.

According to this study, the Druze genome is largely similar to the genome of other Arab populations in the Middle East. They also found a few genetic elements in the Druze genome that originated from Europe, Central and South Asia (the Iran region) and Africa.

Our next step is to try to identify the genetic component of common diseases in this sector using the traditional family structure in a study that will allow genetic decoding of regular genetic diseases and provide data on diseases that have a genetic basis, such as cancer and diabetes. We are also planning similar studies in the future of the Muslim and Christian populations in Israel,” Prof. Friedman, of the Chaim Sheba Medical Centre, Tel Hashomer, concluded.