Abstract
Primates manufacture and use a range of tools for a variety of purposes and exhibit some of the most complex tool use among nonhumans. Chimpanzees and some populations of orangutans, capuchins, and macaques are generally considered to be the most skilled nonhuman tool users and habitually use tools in the wild. A much larger number of primates are capable of tool use but rarely express these behaviors in natural settings. Identifying the factors that are associated with the variable expression of tool behavior across the Primate order and understanding the adaptive basis of primate tool use are ongoing areas of scientific inquiry. Studies of primate tool use provide a unique vantage point on the behavioral ecology, cognition, and culture of nonhumans while also producing critical insights into the evolutionary processes associated with the emergence and flourishing of complex technology within the hominin lineage.