The Aka represent sex roles that have underlying characteristics familiar to all cultures. Some culture in the world must have the most objectively nurturing fathers, and the Aka happen to be it. But, it's the poorer in their society that are nurturing. High status Aka men who have enough resources accumulate multiple wives and offload nurturing onto them. This wouldn't raise the eyebrows of any student who's studied the history of human cultures around the globe. Instead, it'd be shocking if it turned out that high status women married multiple husbands to take care of the nurturing.