Robin Hanson writes:

Consider: what elites did foragers worry most about? Foragers worried most about elite capacity for violence, and an inclination to use it. They also worried lots about unequal access to food and shelter, and to tools useful for all these things. So foragers enforced strong norms against giving orders or doing violence, and norms favoring sharing of food, shelter, and tools. In these senses foragers were egalitarian.

However, foragers worried far less about unequal capacities for art, music, conversation, charm, social popularity, or sex appeal. After all, in a forager world unequal capacities of these sort just couldn’t go anywhere near as horribly wrong as unequal violence or food. Because of this humans seem evolved to tolerate, and even celebrate, unequal abilities in art, popularity, or sex appeal.

As human populations are the descendants of those who survived AND were reproductively successful, I am not sure that Hanson is drawing a useful distinction. If men tolerated inequality in resources OR inequality in mating opportunities when they could do something about it, they would have lower than maximum fitness.

The other conflating factor is that these features - wealth, art, appearance, popularity and so on - are all signals to the opposite sex. Lack of tolerance of income inequality is likely to reflect the effect on reproductive success as much as the consequences for survival. Further, individuals are likely to be better across a spectrum of these traits, with more popular and attractive males also having higher income.

Assuming Hanson is correct in assuming that people worry more about resource scarcity than inequality in abilities in art, sex appeal or popularity, is this because abilities in art, sex appeal or popularity are more difficult to fake? In contrast, excess resources could be acquired through violence (although ability to successfully acquire resources through violence is also difficult to fake). Inequality in sex appeal or popularity can go wrong, but there are more limited means to rectify it. If the ugliest man in the tribe kills the most attractive, he is still the ugliest. The benefits to killing the attractive man would be because he has resources and the killing may raise status, not because it reduces sex appeal inequality.

One interesting piece of evidence about income versus reproductive inequality is about to emerge. As the excess of men in China and India pass through their reproductive prime in the next 20 years, what will trigger the more trouble - inequality in resources or inequality in mating opportunities? We should be able to contrast different regions in those two countries. There may be difficulty disentangling the two as income inequality and inequality in reproductive success are likely to be highly correlated, but the evidence is mounting that excess men are a recipe for trouble.