DNA and genealogy

That there are many subtleties in the application of DNA data to genealogy can be appreciated from a simple observation. A child (except in the case of cloning eg in virgin births if possible!) generally acquires 50% of its DNA from each parent, thus in effect discarding 50% of each parent's DNA. After a few generations it becomes increasingly likely that all of a parents' DNA will have been discarded in that family line. That is, eventually, even though one knows of a direct ancestor, none of that ancestors' DNA may appear in one's own DNA!

This observation does not of course apply in the case of mitochondrial DNA which is transmitted through the female line, and Y-chromosome DNA which is transmitted through the male line.

Nevertheless this is an active field of enquiry, and interesting findings have been made. In a recent study a promising genetic signature of Sephardic Jews is examined (ref 305). An earlier result is cited - from which it emerges that the Ashkenasim, which comprise the largest Jewish population worldwide, shows a prominent founder effect with only 4 mitochondrial haplotypes comprising 40% of the modern population and with the most frequent haplotype found in 19% of individuals. Sephardim, descendents from Spanish and Portuguese Jews who were the largest Jewish population until the 18th century, instead show a large variation in maternal founders of the communities of the Ottoman Empire. This was especially apparent in their results for Turkey, with the 4 most frequent haplotypes found in only 17% of the present day descendent population and the most frequent haplotype found in not quite 6% (for Bulgaria, the numbers are 27 and 8.5%, respectively). The Ottoman Empire, including Turkey and Bulgaria, received many of the Jewish people who were exiled from Spain and Portugal in the late 15th century. The contrasting findings for the two prominent Jewish populations suggest a greater genetic diversity in mitochondrial DNA in Sephardim than in Ashkenasim. However it is noted that the seemingly higher genetic variability in the present-day Sephardic population does not preclude uncovering Sephardic signatures, the object of the study.

Our distant cousin Michael Waas has conducted a study of male-line Sephardic descent in which some of us participated (see ref 306). His collaborator Adam Brown in the online discussion group Sephardic Diaspora during 2019 referred to the Ashkenasi founder effect (see above) and the likelihood that Randy Schoenberg (and hence all of us who descend via the Barrows from Simon Michael Pressburg) does not descend from the small number of original founders of the Ashkenasi community. This discussion is ongoing - but perhaps the ancestors of Simon Michael Pressburg like Moritz Baruh came to the Austro-Hungarian Empire from Italy or elsewhere in the older Roman Empire.

John Griffiths, descendant of Joseph Barrow, has matched his and Julian Land's DNA data on GEDmatch and noted that we have a 3.4 centipoise match on our 8th chromosome which would put a common ancestor in the early 1700s. This of course matches our known common ancestors Simon Barrow 1709-1802 and Bailah Montefiore 1720-73