In an op-ed in today's NY Times, Dr. Benny Morris writes about the origins of the Philistines:
In antiquity, Gaza was part of Biblical Pleshet or Philistia - the domain of the Philistines, a non-Semitic "sea people" hailing from the Greek isles who probably invaded and settled along the coast in the 12th century B.C. (more or less simultaneous with the arrival in the Holy Land of the Hebrews from the east).The implication here is that the Philistines did not live in the land of Israel prior to the Jewish conquest of the land, i.e. in the times of the Patriarchs and the Exodus. Yet, the mentions of Philistines in the books of Genesis and Exodus imply that they were.
R. Shalom Carmy directed my attention to an answer given by the late Prof. Yehoshua Grintz. In a lengthy exposition on the subject in his Motza'ei Doros (pp. 99-129), Prof. Grintz argues that there were two Philistine peoples with different origins, regions and time periods. See here for a summary of his arguments (rather, the simpler of his arguments that do not deal with non-biblical texts).
Interestingly, I saw that Prof. Grintz's mentor, Prof. Umberto Cassuto, quotes approvingly this suggestion of his student in his commentary to Genesis 11:14 (From Noah to Adam, pp. 207-208). While I have not seen it inside, Kenneth Kitchen is quoted as also making a similar argument (Peoples of Old Testament Times, p. 56). Gordon Wenham (Word Biblical Commentary, Genesis 11:14 p. 225) writes:
That the Philistines are linked both with the Cretans and the Casluhim suggests a close association between these two groups. Or it may be that the Philistines of Genesis represent a different group from the Philistines of the post-conquest period.The Philistines of the Patriarchal period did not live in Gaza. They lived in the Negev.
UPDATE: I found the following two articles from Bar Ilan's Parashat Hashavua Study Center that take the same approach: Dr. Michael Avioz and Menahem Ben-Yashar. I'm not sure if they were included in the book Professors on the Parashah.