So, I just posted recently about bonobos and their matriarchal society and apparent deficit of aggression. Bonobos are apparently very sexual creatures, who use sex in part to sort of grease the wheels of social interactions and keep people happy.
People don't really do that. In fact, we pretty much reject that model of society except in some science fiction universes. In a study that reinforces traditional family values, monogamy was found to increase cooperation and the complexity of society. Turns out birds are more likely to help one another if they're pretty sure they're related, which is more likely if monogamy is the norm. It's always interesting to see scientific hypotheses to explain social structures.
Obviously there must be multiple ways for complex societies to evolve since bonobos also live in fairly complex, cooperative groups. I wonder if the gender that monopolized resources makes a difference. Females are more likely to know who sired their offspring, and their parentage is pretty clear. If females are more in charge, then, are they more likely to cooperate with each other and with their sisters' offspring? Too bad I don't know more about birds to be able to ask that question more critically.