I don't know that they would have had a specific conception of their ancestors as such, but some Mesopotamian texts do address this to some extent. the poem Lugalbanda A in particular describes how Lugalbanda, having been left to die on expedition from Uruk, starts a fire(and the texts singles out that he does so with a flint, rather than the normal lowland method), gathers wild plants, and traps wild animals. More to the point, these are depicted as unusual and exceptional skills for a "civilized" man to have:

While the bread was baking by itself, he pulled up šulḫi reeds of the mountains, roots and all, and stripped their branches. He packed up all the cakes as a day's ration. Not knowing how to bake cakes, not knowing an oven, with just seven coals he had baked giziešta dough. He garnished it with sweet date syrup.

Given that this is set in the mountains on expedition it seems reasonable to assume that what is at stake here is that Lugalbanda is uniquely capable of the skills of living outside of civilization and that a contrast is drawn here between settled agrarian life and nomadic, unsettled life-between the raw and the cooked, so to speak.

No, they weren't, just like any other civilization, because nomadic hunters and gatherers didn't keep written records. Instead, just like any other civilization, they had a creation myth. Sumerians had the Eridu Genesis, Babylonians had the Enuma Elish etc.