If that isn’t an odd—and potentially incendiary—query, nothing is.

Yet, in recent times it was sparked by a writer who himself was Jewish.

That was Arthur Koestler, who (famously-infamously) posited in a book called The Thirteenth Tribe that in fact many if not most modern Jews are descendants not of Middle Eastern Jews (like Jesus) but converts from the region of Turkey back in the eighth or ninth century: Khazars who changed their religious identity to avoid persecution by invading Muslims who were targeting what they actually were: Christians.

Oh, those invading Muslims; these days their incursions are quieter, such as their mass immigration to places like France and England.

But back to Koestler:

To be more specific, he proposed that particularly Ashkenazi Jews in Europe, the United States, and Israel are not descended from the ancient Israelites of the Middle East, but from a Turkic people from Central Asia who spread into Eastern and then  Western Europe.

Here’s a question: does the incredible skill Israelis have in waging war draw from a German lineage?

Koestler’s intent was humanitarian rather than political: he sought to dismantle antisemitism by undermining the idea of a Jewish “race.” 

At best, it seems, this idea is only partly valid. 

While genetic research has revealed traces of Khazar lineage through Y-chromosome and mitochondrial DNA analysis, the influence is far smaller than Koestler proposed—more likely the product of gradual admixture than mass conversion.

No need to get too scientific.

A further study from 2010 to 2013 found that Ashkenazi Jews genetically cluster most closely with Middle Eastern and other Jewish populations showed no notable links north of the Caucasus—the historical Khazar territory.

And a 2014 genome-wide analysis across Europe, the Middle East, and Khazaria showed no evidence of significant Khazar ancestry in Ashkenazim; they consistently align with Middle Eastern and European Jewish lineages. 

The major consensus is that Koestler’s thesis, fascinating thought it is, largely remains unsupported. Limited European admixture is traceable, possibly from some Eastern European origins—but not mass Khazar ancestry.

While Koestler reinvigorated interest in a medieval Jewish state to counter racism, both historical rigor and genetic science now overwhelmingly affirm that Ashkenazi Jews derive predominantly from Levantine and European roots—not the Khazars. 

But converts? Might there still be a link to converts who were European?

Yes.

There were significant conversions to Judaism in the first to third centuries A.D. throughout the Mediterranean world, including Italy, Spain, and Gaul. There were Greek, Slavic, and even many Germanic individuals—as well as some Khazars—who became Jews, especially when marrying into Jewish communities or during waves of toleration.

Are modern Jews descendants in the lineage of David?

Many yes, many no.