Which primate is known for having a rich variety of social structures that include polygyny and polyandry?

The correct answer highlights that chimpanzees are recognized for their complex and varied social structures, which can include practices like polygyny (one male mating with multiple females) and polyandry (one female mating with multiple males). Chimpanzee societies are characterized by fluid social relationships and hierarchies, where individuals can exhibit different mating behaviors depending on ecological conditions and social circumstances.

In contrast, the social structures of other primate species differ in significant ways. Tarsiers are small primates that typically form monogamous pairs rather than exhibiting diverse mating systems. Gorillas usually engage in polygynous structures dominated by a single, dominant male and his group of females, rather than a range of social structures. While human beings do exhibit a wide variety of social structures, the direct reference to a primate and emphasis on both polygyny and polyandry specifically aligns with the behaviors observed in chimpanzees. Therefore, the recognition of chimpanzees as embodying diverse and flexible social structures makes them the correct choice.