What does this quote from Walden mean? "Still we live meanly, like ants, though the fable tells us that we were long ago changed into men."

Thoreau
is referring to the fact that in modern society man unthinkingly allows himself to be a small
part of a large collective, just like a worker in a giant colony of ants. And to a staunch
individualist like Thoreau that's a pretty sorry state of affairs. He wants us all to affirm
ourselves as unique, distinct individuals with the power to think for ourselves and lead the
kind of lives we really want to lead instead of blindly going along with what everyone else is
doing.

Theto which Thoreau refers is from Ancient Greek...