A great deal of this move to identify a group of people as the lost tribes of Israel stems from a misunderstanding of prophesy from the OT. They use scriptures such as Isa. 45:17,
" But Israel shall be saved in the Lord with an everlasting salvation: ye shall not be ashamed nor confounded world without end." (KJV)
without understanding the definition of Israel under the new covenant of the gospel of Christ. Some analysis is required.
Under the old covenant, the Israelites were identified by their blood line to be children of Abraham, or proselytes to the faith.
Under the new covenant of the gospel of Christ, all those that are baptized into Christ, have put on Christ, and are counted for the seed of Abraham.
"And think not to say within yourselves, We have Abraham to our father: for I say unto you, that God is able of these stones to raise up children unto Abraham." (KJV)
The blood line was not important any longer, and truly was not important even under the old covenant, as anyone whose faith brought them to a knowledge of the laws of God could become a proselyte, and counted in the congregation.
It was always the faithful of God who were the true Israelites.
"Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all, 17 (As it is written, I have made thee a father of many nations,) before him whom he believed, even God, who quickeneth the dead, and calleth those things which be not as though they were. 18 Who against hope believed in hope, that he might become the father of many nations, according to that which was spoken, So shall thy seed be.” (KJV)
Today, the house of Israel which is saved with an everlasting salvation are all those of the saved under the old covenant, along with all who are in Christ under the new covenant. If we have been baptized (immersed) into Christ, then we are counted for the seed of Abraham, and we are Israel (Gal. 3:26-29).
Those who seek a DNA strand of the blood line have become confused, and are seeking after the old covenant which has passed away.
I have more material that you can use to support your arguments at my blog at ShreddingTheVeil. My posts titled God's Definitions, Part I: The House of Israel, and Part II: The House of God show how these changed under the gospel of Christ.