reets; for if we take the ages into our account, may there not be a civilization going on among brutes as well as men? They seemed to me to be rudimental, burrowing men, still standing on their defence, awaiting their transformation.
Thoreau uses personification here again, and he talks about the history of human evolution. Thoreau saw beasts as creatures with their own histories and civilizations. They just like humans, waiting to evolve. I think it also shows Thoreau's respect for animal life. In his eyes, humans and animals are equal.