Final answer:
Sexual dimorphism in apes often involves significant size differences with males being larger, which can be related to mating systems such as male dominance and polygyny. In humans, sexual dimorphism is less pronounced, with females being about 90% the size of males. The relationship between dimorphism and social structures is complex, and differences in size do not straightforwardly predict behavior or social organization.
Step-by-step explanation:
Sexual dimorphism refers to the size differences between males and females of a species. In many Old World ape species, males are significantly larger than females, which is thought to be a result of evolutionary pressures where one male defends multiple females. Among primates, gorillas exhibit a large degree of dimorphism, with males often weighing more than twice that of females. In contrast, human sexual dimorphism is relatively low; human females on average are about 90 percent the size of males, which is closer to the dimorphism seen in gibbons, where males and females are almost the same size.
Considering behavior, high levels of dimorphism in nonhuman primates, such as gorillas, are sometimes associated with male dominance and competition for mates. In species with lower dimorphism, such as gibbons, there is an association with long-term monogamy. However, the link between biological characteristics and social behavior is not direct, and variations within species complicate the ability to draw straightforward conclusions regarding human social structures based on nonhuman primate models. Adrienne Zihlman cautions against making firm judgments about social behaviors based on anatomical size differences, acknowledging a complex 'mosaic' of sex differences.
In humans, while there are recognizable biological differences between males and females, these differences are small and often influenced by social and cultural factors. Humans, much like their primate relatives, exhibit biological flexibility allowing for diverse gender and sexual expressions that cannot be strictly attributed to biology alone. Moreover, sexual dimorphism can widely vary among all species, and there are cases where traditional roles are reversed, and females are larger than males.