I believe the Philistines were not Semitic and not even Adamic but were Caucasians. I believe they were related in ethnicity with the Phoenicians. That s why you find them along the coast since they were traditionally a seafaring people.
An example is the word ' Palestine '
1Samuel17:10
And the Philistine said, I defy the armies of Israel this day; give me a man, that we may fight together.
That word in the Masoretic that you read, that's an interpolation, the actual word used in the Septuagint is ἀλλόφυλος...