World history can provide a context for regional and national histories, but what is the context for world history itself? If world history is about the history of human beings, asking this question means asking about the place of human beings within modern knowledge. While most traditional cosmologies put humans at the center of the picture, the temporal and spatial scales of modern science are so vast that humans can seem to vanish entirely. Yet if we order the contents of our universe by complexity rather than by size or longevity, things look different. This paper explores arguments suggesting that human societies and their evolution may be among the most complex objects available for scientific study. Such conclusions hint at the significance of world history beyond the history profession and also suggest the extraordinary difficulty of the challenges world historians face.