Evolution is predicated on some distribution of genetically inheritable characteristics with differential survival / reproductive benefits. Depending on a number of other characteristics, one might end up with highly diverse, or highly homogeneous local or regional populations.
In the case of humans, evolution did encourage diversity, if only because it created sexual reproduction in humans, which increases the diversity of offspring. And of course, humans are not all identical today, implying an evolutionary response to different environmental conditions.
I recommend Asimov's article on the matter: http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
It is not a stretch to think that natural selection could apply pressure to traits that are passed on through culture and exposure to ideas.
Peace and have a great day (and an upvote).
It is a monstrous ideology that has produced nothing but suffering.
Have a great day.
That's quite a general statement for the discussion here, which you then use to make a specific conclusion about the human behavioral issue under discussion in this thread. Could you kindly fill out the reasoning steps you are implicitly following with more citations to research on each factual assertion you are relying on?
even though their standard of living is rising continually
This is generally correct. A popular book on the issue (I don't endorse ALL its conclusions, but I like its citation of many different reliable references) is The Rational Optimist.
However, this is just background color, it doesn't change the argument. As long as humans are generically and epigenetically diverse there will be differences in fitness. In capitalist societies it makes people more or less wealthy; in other societies it makes them more or less powerful, or influential, or with more or less social status. There are other factors that can make someone poor but this one seems impossoble to completely remedy.
There is no question genetics play a role, the question is how big of a role do they play? You haven't gotten anywhere close to answering that.
Personally, I disagree that evolution encourages diversity. It seems to me that diversity occurs in spite of it, as a result of our ever changing, dynamic, earth.
Consider a genetic variation that if you inherit one copy you communicate well but if you inherit two copies you stutter. Communicating well will be selected for, but stuttering will be selected against. If the probability of having one copy is P, then the probability of having two copies is P squared. For example, if 5% of people have one copy, then 0.25% will have two. The variation will be selected for until it is so common that the gain in fitness for one-copy people is balanced by the loss in fitness two-copy people. (The real situation is more complicated, since variations in many genes interact to affect each other's fitness.)