So far GalCiv IV sucks big time. There seems to be no way to control population. It just keeps growing and food goes negative until popularity hits zero. Population growth doesn't ever level off and I can't build colony ships fast enough to even put a dent in it. I think there is no such thing as game balance. I can't get a working civ off the ground because it's impossible to manager approval - there is no way to research improvements that I can tell and no tech tree. No way to increase food or stop citizens from multiplying or a way to just kill off unwanted population. The game just doesn't seem to offer much. It's like a crippled version of GalCiv 3.
You seem to forget this game is missing many features and is in pre-release. You can increase food by researching food techs (farming a good one). At this point I can offer the opinion that this game is FAR FAR better than Gal Civ 3. Its mechanix and game play are head and shoulders above 3. Are you playing the mimot or a regular paced race? Mimot grow far far faster than say Humans.
I agree there should be a way to 'dispose' of unwanted population but that is likely to come from new policy cards which will bend into what types of government you can have.