[AndrewC]

There ISN'T a single solution with a GA; there is a solution space (a set of solutions) that have varying degrees of fitness based upon how you weight.

And nowhere in the process of generating those "solutions" is there any hint of the weighing? I really doubt it.

[PugetSoundSoldier]

There is weighting of the results! I've stated that. And the weighting is typically non-linear because the results have different values.

GAs are used where there aren't hard-defined answers like you want. Where you can't exactly quantize every single potential input and output. Where the answer is more like the judge's conclusion on pornography: "I'll know it when I see it".

I'd suggest this as an excellent primer on GAs, and also the Wikipedia page on GAs as good background.

Like so much with life - where the answers/solutions are varied and shaded and fuzzy - GAs excel at operating in those situations.