Sure-- a full-scale nuclear war that collapsed civilization and technology but didn't actually kill every living human would count.

In terms of less grandiose things, if the actual lived experience of being a human changed dramatically with the the invention of important and novel emotions or social structures, I would consider that a fundamental change. Some argue that this actually happened during the medieval period and that romantic love didn't exist before then, but I'm highly skeptical of this claim for multiple reasons.