Everyone who brings up this red herring uses it to claim:

1. Today's Palestinians are descended from the Canaanites the Israelites displaced.

2. Hence they inherit "from the river to the sea" land rights from 3000+ years ago.

3. Jews are transitory interlopers--settler colonialists from time immemorial when it's large numbers of Palestinians who illegally immigrated to mandatory Palestine from Syria, Transjordan, Iraq and Lebanon, attracted by Jewish investment and jobs in the booming port of Haifa.

4. And to distract from the simple fact that there has NEVER been a Palestinian state on the real estate in question; not under the Assyrians, Babylonians, Persians, Greeks, Maccabees, Romans, Byzantines, Muslims after 637 CE/AD, the Christian Crusaders, the Mamelukes, the Ottomans from 1517-1918.

5. And to distract from the PLO's Zahir Mohsein who said in 1977 that Palestinians nationality was purely a tactical invention and that there's no difference between a Palestinian and an Egyptian, Jordanian, Syrian, Lebanese, Saudi. https://en.wikipedia.org/wiki/Zuheir_Mohsen

But the best reply to their false history is a joke:

“Sharon sits down with Arafat at the beginning of negotiations regarding the resolution of the conflict. Sharon requests that he be allowed to begin with a story. Arafat replies, “Of course.”

Sharon begins his story: “Years before the Israelites came to the Promised Land and settled here, Moses led them for 40 years through the desert. The Israelites began complaining that they were thirsty and, lo and behold, a miracle occurred and a stream appeared before them. They drank their fill and then decided to take advantage of the stream to do some bathing — including Moses. When Moses came out of the water, he found that all his clothing was missing.

“Who took my clothes?” Moses asked those around him.

“It was the Palestinians,” replied the Israelites — “

“Wait a minute,” objected Arafat immediately, “there were no Palestinians during the time of Moses!”

“All right,” replies Sharon, “Now that we’ve got that settled, let’s begin our negotiations.”

This is how to do a proper title search in real estate.

But it won't convince those brandishing the genocidal slogan "from the river to the sea", which is what the vast majority of "Palestinians" want:

https://medium.com/the-judean-peoples-front/palestinians-say-what-they-want-eaab778266b8