How did the Samaritans originate?
The Samaritans originated from remnants of Israel's ten tribes who returned and established worship at Samaria. They intermarried, adulterating their bloodline and worship, and set up a false temple. Because they became half-breeds, the Jews of Jesus' day hated them and avoided Samaria, though they remained more Jewish than Gentile.
Les explains that when Peter says "all the house of Israel" in Acts 2:36, he means all of Israel, not just two tribes, so the ten tribes are not lost. Parts may have disappeared, but some came back and set up worship at Samaria. These became the hated Samaritans of Jesus' day because they were half-breeds: they had intermarried, adulterated their bloodline, and adulterated their worship, setting up a false temple. Consequently, the Jews of Jesus' day would not even go through Samaria. Yet they were still more Jew than Gentile, so when Jesus talks to the woman of Samaria at the well, Les maintains He is talking to a Jewess, not a Gentile.