Which primate group demonstrates the most sexual dimorphism?

The primate group that illustrates the greatest degree of sexual dimorphism is indeed the group characterized by a single-male social structure. In these groups, one male typically mates with multiple females, which creates a scenario where the male must compete for access to females. As a result, males often develop larger body sizes, more pronounced secondary sexual characteristics (such as larger canine teeth or more robust musculature), and variations in coloration compared to females. This pattern of sexual dimorphism is often driven by sexual selection, where traits that enhance a male's chances of attracting mates and successfully reproducing become exaggerated.

In contrast, groups that are monogamous tend to show less sexual dimorphism, as both sexes often share similar roles and there is less competition among males for mating opportunities. Similarly, polyandrous groups, where one female mates with multiple males, may also have reduced dimorphism due to the more balanced mating strategy compared to the highly competitive single-male groups. Multimale groups may have some level of dimorphism, but it generally does not reach the extremes seen in single-male groups where the competitive pressures are more intense.