<p>Plants have often been considered peripheral to the human story until the relatively recent past, only starting to become significant to human diet in the Epipaleolithic when hunter-gatherers were thought to incorporate a range of previously ignored foods into their diets, including grass seeds. This was argued to have laid the groundwork for an increasingly intertwined relationship between hunter-gatherer communities and cereals, eventuating in plant domestication and agriculture. In this paper, we review the evidence for Flannery’s ‘Broad Spectrum Revolution’ and the early use of plant foods globally. We argue that broad-spectrum plant use, including complex plant processing, is a normal characteristic of early human groups and was a critical factor in the successful peopling of new environments globally, rather than a step <i>en route</i> to agriculture. We are a broad-spectrum species, and the ability to process a wide range of plant foods represents a key threshold in hominin evolution.</p>