By definition, the smallest unit that can evolve is a population.
That's the Biological Evolution definition, but there are other kinds of evolution.
If we make better people through genetic engineering, it's called "gattacarization" or some other damn thing, but it's not evolution.
Cool; I learned a new word. Did they coin that after the movie Gattica or vice versa...?
So anyway... either by gattacarization or by cybernetics I'm pretty sure whole populations of humans (and eventually robots) will evolve themselves during the next century... unless of course Iran drops an EMP over everybody, or the NWO turns on Big Brother in full force or WWIII breaks out... etc.