Interesting... 
While biological causality is extremely difficult to prove and this does not prove it, it suggests that the communist view of wealth and wealth creation is simply wrong.
Sociological studies, however massive or longituninal, fail to take into consideration numerous other factors that account for the differences.
In China, for example, the pre-revolution elites such as capitalists sold their assets to the gov and some of their personal wealth were also confiscated by the young red guards during the heat of revolutionary fervor, but these people are still much richer than the ordinary working class. The role of such legacy should not be neglected.
@matrix
A short paper cannot account for a myriad of factors that were involved in a highly complicated historical period. For the sake of convenience, it's okay to leave out those uncontrollable variables.