Talk abstract: Understanding the mechanisms that give rise to the emergence and evolution of tool-use traditions across the primate phylogeny are germane to the evolutionary origins of human cognition and culture. Long-tailed macaques are the most recently discovered of just three primate taxa to use stone tools in the wild. The species occupies a wide geographic distribution that encompasses a diverse range of habitats across Southeast Asia, yet stone- tool use appears limited to one subspecies inhabiting coastal habitats between Myanmar and southern Thailand. This unique pattern of traits present unprecedented opportunities to examine phylogenetic, ecological, and cultural hypotheses for the emergence of technical intelligence and traditions in primates, as well as the significance of coastal resources to primate adaptation. In this talk, I will present current knowledge and outstanding questions surrounding the development, transmission, and adaptive significance of coastal stone-tool use, emerging from research on macaque populations in Thailand.