[yarddog]

I had always assumed that the Palestinians were descendants of the Philistines but archaeologists say no.

It does seem they were a pretty fair opponent of the Israelite’s. Often winning against them.

[Verginius Rufus]

The Philistines first appear as Peleset among the so-called Sea Peoples attacking Egypt. They were in a small part of the Holy Land. Herodotus already in the 5th century BC refers to "Palaistine Syrie" (1.105) and to "the Syrians in the Palaistine" (2.104) but it isn't clear how large an area he meant by that--no doubt the Philistine area but maybe more. Of course the Romans later used "Palaestina" in a wider sense.

At the time of the Muslim invasion in the 7th century, the Holy Land seems to have been predominantly Christian with Jewish and Samaritan minorities (but I don't know the proportions or if there were still some pagans). In the 19th century before the Zionist movement started the country was Arab speaking and majority Muslim but with Christian and Jewish minorities. The Christians were probably descended from the inhabitants of the 7th century (maybe a bit of Crusader ancestry too). The Muslims could have been descended largely from the 7th-century inhabitants too if their ancestors had converted. There must have been some immigration from Arabia but there wasn't a huge population in Arabia to begin with and the Muslims also went to other places like Egypt and Iraq. There would also have been slaves brought in from various places during the Middle Ages and later.

I think it is mistaken to assume that modern Palestinian Muslims are all descended from Arabian immigrants. DNA studies seem to show a relationship between Palestinian Arabs and Jews as if both groups have ancestry going back to the people there in Biblical times. (Of course we know that the Jews are descended from the Israelites.)