[Firestone]

Het "onderzoek" van Koestler (die overigens geen historicus was) over de Khazaren was alles behalve wetenschappelijk.

Wikipedia (met bronnen) is een goed vertrekpunt voor een serene analyse van dat Khazaren-verhaal.

Twee citaten (bronnen in het Wikipedia-artikel):

This theory… is supported by no evidence whatsoever. It has long since been abandoned by all serious scholars in the field, including those in Arab countries, where the Khazar theory is little used except in occasional political polemics.

Bernard Lewis

Recent DNA studies on the Y-Chromosome of Ashkenazi Jews showed they had an "extremely close affinity [with] non-Jewish Middle Eastern populations", indicating "a common Middle Eastern origin", as does the mitochondrial DNA (mtDNA) of at least 40% of the current Ashkenazi population. So although Khazars might have been absorbed into the Jewish population it is unlikely that they formed a large percentage of the ancestors of modern Ashkenazim.

Een gedetailleerde en recente bron: Are Russian Jews Descended from the Khazars?

De weinig verrassende conclusie:

East European Jewish ancestry originates substantially from ancient Judea, and the same is true of most other modern Jewish populations (with the exception of groups like Libyan Jews and Ethiopian Jews). But, it is rational to conclude that some Jews also have some Khazar ancestors.