What Scholars Propose
For the original population, as distinct from today's Jewish population (see above): Currently biblical scholars recognize three possible scenarios explaining Israel's rise to power in Canaan:
1. the Conquest theory: that Israelites came in from the outside and conquered the land;
2. the Peaceful Settlement theory: in which it is argued that Israelites entered gradually, settling in the sparsely populated areas of the central highlands; and
3. the Peasant Revolt or Social Revolution theory: that Canaanites rose up against their overlords. see link The Problem of Israel's Origin
http://wiki.answers.com/Q/Where_did_the_Jewish_people_originate Read more: http://wiki.answers.com/Q/Where_did_the_Jewish_people_originate#ixzz1zgCyj8xm
You are of course welcome to believer any of these theories.
However, the Bible is quite clear on what it says happened.