It's pretty simple: Humans are diverse. Evolution created humans. Therefore, evolution created human diversity. "Encourages" is perhaps the wrong word--evolution really produces diversity because it responds to the diverse conditions of the earth.

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.

When you say "it's pretty simple: Humans are diverse" you are still making a pretty nebulous statement. What does diversity even mean there? On what basis are you resting your argument that evolution created human diversity, and is not in fact working against it? How do you compare genetic diversity to socioeconomic diversity in a way that is useful or sheds light on their actual relationship?

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.