Earlier quoted context omitted.
The 2-3000 years of history are entirely and wholly irrelevant. Especially as history shows clearly that the Palestinians are just as much the descendants of the ancient Israelites as the Jewish diaspora that returned to their modern land after the founding of modern Israel. The old population from before the Roman conquest never disappeared - some departed and formed the diaspora, but most stayed. Some converted to…
Is your claim that genetics determines who should live in a particular patch of land?
I.e., the following is, I believe, a reasonable argument:
"I should have a right to live in this general patch of land, since my grand-parents lived here. Maybe my parents moved away and I was born somewhere else, but they still had a right to live here and I should have it too. I may have to buy some land to have this right, I'm not saying I should be given land - but I should be allowed to do so. Additionally, it matters that my grand-parents were not invaders to this land. Their parents and grand-parents had also lived here, and so on for many generations."
This doesn't imply genetic heritage necessarily - cultural heritage and the notions of parents are not necessarily genetic. I might have ~0% of the specific DNA of some great-great-grand-parent (or even 0% of my parents' DNA, if I am adopted) - but I'm still their descendant. Now, how far you want to stretch this is very much debatable.