If "Palestinian" is taken to mean all non-Jews living in the area between the Jordan River/Dead Sea and the Mediterranean as of 1917 and their descendants (mostly Arabic-speaking but some Armenians, Circassians and perhaps others), they are probably a mix of all the populations which have lived in the area since antiquity--Canaanites, Philistines (immigrants from the Aegean?), Israelites, Greeks, Romans, Arabs, Crusaders, etc. The Christian population of Palestine in the late Roman period was probably partly descended from Jews who had converted.
Even if the Arabs imposed their language, it doesn't necessarily involve a large influx of people from Arabia--compare how the Spanish language took hold in parts of Latin America where the Spanish colonists were outnumbered by the indigenous population.
So DNA studies should show some kinship between Israeli Jews and at least some of the Palestinian Arabs.
A Jewish girl who had lived there told me as much.
She said, “It’s ridiculous, we’re all Palestinians...it’s a place.”