> Why do men who have a partner already feel obliged to continue capturing more and more resources?

Great question. I think there are strong forces and dynamics that push us to earn more and "improve", constantly, regardless of whether we have a partner or not. It's kindof what a capitalistic society is built upon. If we didn't consume much gdp wouldn't grow right? If we didn't compete how would earnings increase? It's coming from peers, parents, spouses and from the way society itself is structured. I think it doesn't have tons to do with genes or evolutionary instincts though they may also explain some of it.