One would generally assume that all variations within a species are adaptations to their specific environment, but I really can't see how Africans having big lips or Asians having slanted eyes is beneficial to their environment.
Then again, it could be in some way that isn't overtly apparent. Perhaps Africans thought big lips were attractive and the individuals with bigger lips just happened to mate more? Perhaps something simmilar with Asians and their eyes? Maybe big lips are a random side effect of some important variation in Africans, I dunno...
For slanted eyes, it has been suggested as a cold-adapted feature. The Slant is in part due to extra fat around the eye. this would protect the eye during cold weather. However, there have been sexual selection for the slanted eye. Nowadays, several people find the asian type of eye attractive and this could off been the case several thousand years ago.
As far as the lip is concerned, it has been suggested that bigger lips would increase losing heat in warm temperature. I wonder if there is any correlation between different continent, lip size and climate. This would, to some extent, support big lip as a hot climate adaptation.
In primates, lip configuration is indicative of feeding behavior.
Also, people coming from africa might had a different lip form. We know a bottle-effect and founded effect have occur after people came out of africa. This would have change the frequency a certain lip configuration and this would give some explaination.
Well here's a different take on how slanted eyes could be an adaptation. Have you ever gone outside on a bright, sunny day? What do you "automatically" do?...Squint your eyes. Asian ancestors most likely originate in sunny tropical climates.
Ian: could you elaborate on how lip configurations indicate feeding behaviors in primates?
And just to add an anecdote to hitssquad's riposte, I take a long walk every afternoon when the wind chill is over 16 degrees F. So I have experience with sun, snow and squinting. Recently we have had a lot of snow and the walk took me past fields completely covered with it. The squint problem was much worse than anything I experiences in the summer. Note also that in the winter, the sun is lower in the sky and if you are turned that way, much more apt to shine in your eyes. In the tropics the sun spends much of its time nearly overhead.