What foods were available to my ancestors, and the ancestors of most of the Western world, before grain agriculture?
Wheat made it to Europe about 5000 years ago. By that time sheep had been used for 3-5000 years already, hunting and fishing were daily labors, and foraging for nuts, berries, and greens was done in the short springs and summers. Although some sheep milk was used, it was mostly left for the lambs. Bird eggs and smaller animals were probably taken when possible.
I don't have any sheep. Not really a fan of the taste anyway. But I can get fish, fowl, beef, and pork, eggs, nuts, berries and greens.
If I were that guy about 6000-8000 years ago, I would make sure my greens were planted near the shelter, I would keep sheep if I could. I might cut back the trees shading my favorite walnut tree and keep the weeds away from the berry bramble. You don't have to be a horticulturist to think of that. I might eventually learn to herd the reindeer once a year and I would be careful not to hunt the local pigs to extinction.
So, that's a diet of all available meats, a little salad, some roots, and occasional nuts and berries. Very much like Paleo, except for a few little things.
Some dairy. Probably cheese, although some of the earliest cheese making was about 8000 years ago.
They probably used some herbs, which many paleo folks avoid. I use herbs which my ancestors could not have had, like peppers from the Americas and Asia. I use fermented foods which are probably more recent than cheese, maybe 4000 years old. These things I do because my food is too clean. I don't have bitter herbs in my foraging basket, I don't have dirt on most of my food. I'm not a microbiome fruitcake, but we do need some gut bacteria and I don't have my appendix anymore to store them.