Brandon has a very nice post regarding Aquinas and government:
With regard to the good ordering of the government of some city or nation, two things must be attended to. One is that everyone should have some part in the government, for through this is conserved the peace of the people, and everyone loves and takes care of such an ordering...And in the same spirit:
-- Summa Theologiae 2-1.105.1
"If to provide itself with a king belongs to the right of a given multitude, it is not unjust that the king be deposed or have his power reduced by that same multitude if, becoming a tyrant, he abuses his royal power."
-- On Kingship, I:6
We also have his thoughts that a multiplicity of species across time and space is a positive good: creation participating in the infinity of God. There is a two-part post on why evolution is a fitting way for God to create species, here and here. And in line with this, we have Thomas' thought on where new species would come from:
Species, also, that are new, if any such appear, existed beforehand in various active powers; so that animals, and perhaps even new species of animals, are produced by putrefaction by the power which the stars and elements received at the beginning.
-- Summa theologica, I.73.1 reply3