There is an arguement about cases of a genetic history between many Jews but not all by any means. Anyone who accepts the yoke of Heaven: Torah, is a Jew. Picture it as a Nation with a common culture, common faith and now a homeland. If a Negro from Khartoum, an Arab from Dubai or Joe Smith from Ashland Kentucky decided to embrace Torah and become a Ga'ar (pronounced
g-air): convert they would be just as Jewish as any other Jew. Obviously there would be racial/genetic differences being Caucasian and Hamite.
This is one of the tragedies of Jewish history and being a subjugated people. No matter how much the Jew, according to Halacha, advocates nationalism, individual identity and keeping culture and faith alive amongst their own there has been many examples of exploitations under their rulers. In the Islamic world as "dhimmi" many Jewish families had their familes distroyed and/or vanquished by the Mohammadan conquerer. Many examples being the massacres of all males over the age of 13 and the children and women sold into slavery, herems and what not with obvious intentions of forced conversions and bastard mongrel Children, often raised Jewish by the mothers...
This happened time and again, rapes during the crusades, pogroms and inquisitions etc. which has, in many cases, molested the argument of a DNA link... Now there are a few families that can trace their lines back to antiquity; two being in Israel and one in London England.
I will not keep you.. just my two cents...