This is what my schooling and study has taught me… to begin with, Israel was a people, the descendants of Jacob whose name was changed to Israel. The descendants of the twelve male children became the twelve tribes; Reuben, Simeon, Levi, Judah, Dan, Naphtali, Issachar, Zebulun, Gad, Asher, Joseph and Benjamin. By the time of the exodus aliens (non-native Israelites) who took on the way of life of the Israelites and took Υеhôvâh (`Ădônây) as their God were also included in the community. All through the rest of the Old Testament there are provisions for non-natives to be included, so now it becomes a matter of heart and obedience.
When the kingdom divided in 931 BC Judah and Benjamin became the southern kingdom of Judah with Jerusalem as their capital. The remaining ten tribes of Israel became the kingdom of Israel and eventually made Samaria their capital. Two hundred and nine years later this northern kingdom was taken into Assyrian captivity. What happened to them after this? Are these the Samaritans spoken of in the New Testament? I understand the southern kingdom went into Babylonian captivity and this is the point in history when they became known as men of Judah or Jews. They eventually returned to Jerusalem to rebuild their temple. I assume that these are the ancestors of those we call the people of Israel today.
But what of those other 10 tribes? And if it is a matter of blood lines is it not possible that after more than 4000 years most, if not all people on the earth today have crossed the genetic lines of Israel somewhere in their family history? Is it possible that the bloodline has defused to such a degree that it now include most or even all of humanity today?