Prehistory covers the period of some 4 million years before the start of written history, when our earliest ancestors, the Australopithecines, existed in Africa. But this is relatively recent compared to whole history of the earth of some 4.5 billion years. A key aspect of prehistory is that it provides a sense of scale, throwing recent ways of life into perspective. Humans and their ancestors lived in many different ways and the cultural variety we see now is just a tiny fraction of that which has existed over millions of years. Humans are part of the broader evolution of landscapes and communities of plants and animals, but Homo sapiens is also the only species to have made a real impact on planetary systems. To understand such an impact, we need a grasp of our longest term development and ways of life.