Humans also happen to be super competitive, and downright hostile. The "leveling" the article speaks about has been tried: it's strong government on social-democratic principles. It works. And it gets abandoned as soon as general wealth has risen enough. Egalitarianism and democracy are, strangely enough, not natural partners. The article doesn't even mention it. Unfortunately, there's no link to the paper, so there's no way to tell what the assumptions are. In fact, I can't even find the journal.