  The same distinction underpins Lucretius’ account of the history of culture. Early conceptions of value were reversed as humans became more sophisticated; so, bronze was originally valued higher than gold, as it was more useful, but gold came to be prized more highly (5.1241 ff.). Men learned from the birds how to sing and please the ear; they enjoyed themselves after their rustic picnics, pleasing their bodies without much effort when they began to dance without a regulated rhythm (numerus), which made them smile and laugh and helped keep them awake. Now too, guards keep awake in this way, and they have learned to respect regular rhythms, but they do not enjoy themselves any more than did their primitive ancestors (5.1379 ff.). In general, Lucretius says, human labor is vain and the development of the arts led to misery and war (5.1430 ff.).