Yup, that’s what makes it quite possible. Not drop-dead obvious, though—there’s nonzero selection pressure for intelligence even now, environment has a huge load to do with intelligence so there are possibly big gains between the beginning to civilization and now, maybe civilization-making magic happens with enough geniuses (genii?) or is prevented by too many too stupid people so variance (and maybe population) matters more than average.
Yup, that’s what makes it quite possible. Not drop-dead obvious, though—there’s nonzero selection pressure for intelligence even now, environment has a huge load to do with intelligence so there are possibly big gains between the beginning to civilization and now, maybe civilization-making magic happens with enough geniuses (genii?) or is prevented by too many too stupid people so variance (and maybe population) matters more than average.