Male reproductive variance is greater than females'. Reciprocity is facilitated by individual recognition and long-term memory. Natural selection favors traits improving reproductive success. Resource-defense polygyny is expected in areas where critical resources are unevenly distributed and clumped. Baboon males have larger canines and body size than females.
Human females have larger breasts and hips than males.
Species are reproductively isolated from each other. Living on the ground. Humans are terrestrial. Composed of one dominant mate, several females, and their juvenile and infant offspring. E.g., Hanuman Langurs, Gorillas.