“Since genetic survival is contingent on scarce energy resources, reproductive processes inevitably involve competition, which in turn drives evolution in response to natural selection. As a result, behavior of organisms is adaptive if it increases the chances of reproductive success.”
To put it another way, it was more useful reproductively for men to possess a harem of females than for females to possess a harem of males.
“Typically, resources, status, and power co-varied with reproductive success for males. In general, the acquisition of symbolic capital – honor, prestige, and power – translated into the accumulation of material capital, which enhanced reproductive success.”