What would such evidence look like? I don't think we can consider brain size definitive, since it's possible for humans with about ~10% of our normal brain volu

What would such evidence look like? I don't think we can consider brain size definitive, since it's possible for humans with about ~10% of our normal brain volume to function normally. There seems to be no evidence for tool use, much less advanced technology, but again, what would these even look like after so many millions of years? I think about all we can say is that no prior species changed the planet in the same fashion we have.