Which of the following is an example of primate material culture observed in the wild?

Using stones as tools is a well-documented example of primate material culture observed in the wild and illustrates a significant aspect of the cognitive abilities of some primate species. Tool use, particularly with stones, showcases an understanding of cause-and-effect relationships, as primates manipulate natural objects to achieve a specific result, such as cracking open nuts or accessing food. This behavior is often passed down through social learning, where younger individuals learn by observing older members of their group, thus indicating a cultural aspect to their behavior.

In nature, various primate species, including some chimpanzees and macaques, have been observed creating and utilizing tools to enhance their foraging efficiency. This contrasts with other behaviors, such as making nests or feeding behavior, which are generally more instinctual and do not necessarily require the same level of cognitive processing or cultural transmission. Building shelters is also less commonly associated with primates in the wild compared to tool use, as it typically involves more complex planning and forethought, which, while impressive, may not universally represent culture in the primate realm like tool use does.