Here's some interesting info about Kamina City....straight from the folks at Gainax.
http://www.gainax.co.jp/anime/gurren-lagann/rifling05.html
Some info:
a) Kamina city human population = 300,000
b) Pretty weird social scale
c) Most beastmen living in Tepellin joined humanity thanks to Nia's influence. She also asked them to raise the sleeping newborns.
d) Ganmen battles are the popular underground sport, although Ganmen themselves are illegal in the city for being dangerous weapons rather than "sport" tools. A few outsider beastmen and humans sell weapons and gunmen to people outside the view of the law.
e) The number of resistance forces against the government is fairly big both in humans and beastmen. Weirdly, most beastmen that don’t follow the government are led by former direct enemies of Simon and the Dai-Gurren as if his influence had given them a higher degree of freedom and self-awareness.