Definitions of our species as unique within the hominin clade have tended to focus on differences in capacities for symbolism, language, social networking, technological competence and cognitive development. More recently, however, attention has been turned towards humans' unique ecological plasticity. Here, we critically review the growing archaeological and palaeoenvironmental datasets relating to the Middle-Late Pleistocene (300-12 thousand years ago) dispersal of our species within and beyond Africa. We argue, based on comparison with the available information for other members of the genus Homo, that our species developed a new ecological niche, that of the 'generalist specialist'. Not only did it occupy and utilize a diversity of environments, but it also specialized in its adaptation to some of these environmental extremes. Understanding this ecological niche provides a framework for discussing what it means to be human and how our species became the last surviving hominin on the planet.