Greek and Roman authors frequently coupled their theories of the origins of life on earth with sketches of the primitive existence of the first human beings, and of the subsequent landmarks in the development of civilisation. Myths about a rise from the earth or a fall from the heavens continued to express the conflict in and among ancient writers about the history of the human status. With the cultural histories came value judgements, and more specifically the desire to assign an ascending or descending scale of values to the historical process. Changes in historical outlook may also have been linked with political and economic changes. Early on in the fifth century BC, the Greeks successfully repelled two invasions from the mighty Persian Empire, and were probably beginning to feel a high degree of confidence in their civilisation. Cosmic cycles of the kind outlined by Xenophanes must surely have been accompanied by large-scale cultural transformations.