Originally posted by ForAiur
The former Khazar people are known as the Ashkenazi Jews (plural Ashkenazim) and some writers estimate that perhaps 90% to 95% of those calling themselves 'Jewish' worldwide are ancestors of the Khazars.

Advanced genetic testing, including Y-DNA and mtDNA haplotyping, of modern Jewish communities around the world, has helped to determine which of the communities are likely to descend from the Israelites and which are not, as well as to establish the degrees of separation between the groups. Important studies archived here include the University College London study of 2002, Ariella Oppenheim's study of 2001, Ariella Oppenheim's study of 2000, Michael Hammer's study of 2000, Doron Behar's study of 2008, and others.
Key findings:

The main ethnic element of Ashkenazim (German and Eastern European Jews), Sephardim (Spanish and Portuguese Jews), Mizrakhim (Middle Eastern Jews), Juhurim (Mountain Jews of the Caucasus), Italqim (Italian Jews), and most other modern Jewish populations of the world is Israelite. The Israelite haplotypes fall into Y-DNA haplogroups J and E.

While the Israelite kingdom clashed with a number of world powers over the centuries, including Egypt, Babylon, and Persia, it was the Romans who would destroy the Second Temple in 70 CE, violently sacking Jerusalem and scattering the Israelite population from their homeland. Many Jews were taken as slaves to Rome and its colonies (Konner 2003, p. 86). This watershed moment in the history of the Jewish people is often considered by many researchers to represent the true beginnings of the Jewish Diaspora.

Ironically, however, many scholars believe the Ashkenazi population probably had its earliest roots in Rome, where Jews began to establish communities as early as the second century B.C. While some of these Jews were brought to Rome as slaves, others settled there voluntarily. There were as many as 50,000 Jews in and around Rome by the first century CE, most who were “poor, Greek-speaking foreigners” scorned for their poverty and slave status (Konner 2003, p. 86). Eventually, however, many of these slaves gained their freedom, continuing to live in and around Rome.

By the first century, however, the Jewish Diaspora had already spread to a number of regions of the world, many of which may have contributed to the make-up of the early Ashkenazi Jewish community. These include the Aegean Island of Delos, Ostia (a main port of Rome), Alexandria, and other places in Macedonia and Asia Minor (Konner 2003, p. 83). Jews also began to migrate north of the Alps, probably from Italy (Ostrer 2001).

By 600 CE, Jews were present in many parts of Europe, with small settlements in Germany, France and Spain. More to the east, there were also small Jewish settlements along the Black Sea, as well as larger communities in Greece and the Balkans (Konner 2003, p. 110).

By the 12th-13th centuries CE, Jews were expelled from many countries of Western Europe, but were granted charters to settle in Poland and Lithuania (Ostrer 2001). The Ashkenazi Jewish population expanded rapidly in Eastern Europe, growing from an estimated 15,000-25,000 people in the 13th-15th centuries, to two million by 1800 and eight million in 1939 (Ostrer 2001, Behar 2004b). Thus, Jewish settlement in Eastern Europe became the dominant culture of the European Jews, and then of most Jews throughout the world.