"...populations." You just stated it -- other indigenous populations could be anyone.
As Dr. Alfred Liliennthal, himself a Jew, said, almost everyone could trace their genes back to the Middle East if they trace back far enough. 10 of the tribes were lost during the Babylonian exile -- that's a very long time ago.
And as far as the "Khazars theory has been disproven," that's quite a statement with no link or reference to back it up.
Not that any of this matters, of course, because inheritance in the true Promised Land has always been by faith, never by blood.