Changing marriage systems in the Jewish communities of Israel

The rates of consanguinity among the parents of babies born in Israel during 1955‐57 were estimated by screening the maternity wards. First‐cousin marriages ranged between 1 and 2 % in Ashkenazic Jews, while the majority of the other Jewish communities exhibited far higher rates of consanguinity. There is little basis for the assumption that the incidence of cousin marriages in Jewish groups reflects the sizes of the isolates in the diaspora. The non‐randomness of such unions finds expression in the distinct preference for marriages between the children of like‐sexed sibs. Cousin marriages between persons originating from different countries testify to some amount of gene flow, which occurred in the recent past between the different groups in the diaspora. Among several ethnic groups, the marriages concluded after immigration to Israel exhibit a trend towards declining consanguinity rates. While this tendency might merely indicate the break‐up of the smaller isolates, which have hitherto existed within the communities, a process of merging between these larger units has also set in on a very large scale. Ashkenazic Jews originating from different countries intermarry at an increasing rate. At present only a minority of persons belonging to the smaller Ashkenazic groups choose partners of identical origin. Around 10 % of Ashkenazic Jews contract marriages with members of the other communities. Intercommunity marriages between the various non‐Ashkenazic congregations are also very common. A rough estimate of the genetic risk involved in consanguineous unions was obtained by comparing the mean numbers of live children after different durations of marriage in cousin families and others. In two out of five such comparisons, the cousin families exhibited a small but significant disadvantage. However, no difference in family size could be detected between mothers, who are offspring of first cousins and all other mothers in the sample. We are greatly indebted to Dr Shaul Merin, who participated in some of the field work during this survey. In the sorting and evaluation of the data we were assisted by Fredy Gruber, Sarah Rapaport, Navah Bloch and Elisheva Barak. It is a pleasure to acknowledge the courtesy and co‐operation of the medical authorities and the nursing staff of the following maternity wards: Rambam Government Hospital, Haifa; Rothschild Municipal Hospital, Haifa; Hadassah Municipal Hospital, Hakirya, Tel‐Aviv; Governmental Hospital, Tsahalon Division, Jaffa, T.A.; Beilinson Hospital, Petah‐Tiqwa; Hadassah University Hospital, Jerusalem; Bikur Holim General Hospital, Jerusalem; Shaarei Tzedek, General Hospital, Jerusalem. We are also much obliged to Prof. R. Bachi, Director of the Central Bureau of Statistics, Government of Israel, for consultations and references.