Final answer:
Primatologists associate low sexual dimorphism in gibbons with their frugivory diet and their territorial nature. However, the relationship between these biological and behavioral traits is not straightforward and varies across different primate species.
Step-by-step explanation:
Primatologists thought that low sexual dimorphism in gibbons was a direct result of their frugivory and territoriality. Gibbons, known for their arboreal lifestyle and long arms for tree-swinging, exhibit low levels of sexual dimorphism, meaning males and females are not markedly different in size, although they may differ in color. This characteristic is often associated with long-term monogamy. Comparatively, species with high levels of sexual dimorphism, like gorillas, often have strong male dominance, rigid hierarchies, and high male competition for mating. However, it is important to note that though there might be an association between dietary habits, territorial behavior, and sexual dimorphism, each primate species has a unique combination of these characteristics, and they don't always predict sexual behaviors or social organization, as noted by anthropologist Adrienne Zihlman.