In every generation of humans, there will inevitably be a portion of the population that are too ugly to breed, and will die. Therefore, in the next generation the "ugly cut-off point" will be raised, as there will still be a portion of the population who are too ugly to breed. Of course, they will be more attractive than the previous generation, but still too ugly to find a mate. So gradually the species will become better looking. The reason people don't notice this is because it happens very slowly. So yes, we are getting more attractive, in the same way that peacocks are getting bigger tails and deers are getting bigger antlers.
So, Nickbe's explanation is wrong, and Kneghtrider is correct. To say that ugly people will remain in the population because unattractive people will reproduce with each other does not work, as the trend is still leaning towards good looking people. Ugly people and goodlooking people <i>both</i> want to mate with good looking partners. To suppose that ugly people will remain in the human population is to suppose that peacocks with short tails will remain in the population because all the "ugly" peahens will be left to mate with them. Actually, the trend is towards peacocks with longer tails, and this can be seen in nature. Similarly, the trend is towards "attractive" (to the opposite sex) male humans, and this can also be seen.
By the way, the theory of evolution is not on "shaky grounds", and i'm not too sure where you heard this. On the contrary it is backed up by so much evidence in its favour that it is considered as fact by nearly all scientists.
