In CivIV, your food production is added to your "hammers" to build settlers and workers. While building these units, it sometimes helps to check your city screen as there may be changes you can make to your citizen distribution to build those units sooner.

For example, in a recent game, I had a very high growth city. When I first selected the settler unit to build, the following was my city screen:

The distribution of citizens above is a decent mix of food and production in the early stages of city growth. It allows for decent growth with enough production to pump out some units.

But, when building settlers and workers, food becomes more important. "hammers" are still used in settler/worker production, but sometimes you can make enough of a gain in food that you can cut production time by relocating citizens.

See below (from the same turn) the difference it makes relocating two citizens to a higher food tile:

This is a full 2 turn advantage from the previous setting. This could be the difference between beating your opponents to a prime city location or being left out in the cold (or on the tundra).

When you are through building the settlers/workers, you would either leave the settings the same for massive growth, or switch back to a more mixed setting as in the first picture.

This kind of change isn't always possible, but should be taken advantage of when the opportunity presents itself.

I'm just sad they took away the "add worker to population" feature from Civ II

DD

About workers: In civ3 you need at least one worker per city. In civ4 I can do with less than that. Maybe 1 worker to 2 cities is already enough and this is a good thing.

As set in the example above by mongoose, you can swap out a 2-hammer/1-food tile with a five-food tile, and get a lot more production out of it.  If you have a size four city, with two fish, pigs and sheep on grassland, you are cranking out 23 build units/turn when you add your city square.  That'll build two workers in five turns.

Or am I misunderstanding your concern?

DD