I think too much attachment to humanity, in its historical incarnation, is misplaced. Those periods of coherent, functioning civilization may end up just being the gentler slope of the asymptote before things started going nuclear. The same underlying tendencies have always been present in us, they just weren't manifesting at the same scale.

"Coherent and functioning" sounds great, but in practice that coherence was usually bought on credit, by pushing negative social externalities somewhere out of sight. Those externalities are more easily ignorable when the boundaries of the world are smaller. Just push the trash into the river; just tie the witch up in the forest. Just shut up and marry, girl.