What is the theme in The Songlines by Bruce Chatwin?

Chatwin cites examples throughout his storytelling of civilizations whose languages began with songs, and who lived harmoniously with nature and cultures around them before they settled down into one geographic location and started competing against other groups of people for dominion over territory. Conjoined with the idea that man is instinctively and most naturally a wanderer, Chatwin posits that man is celebratory and peaceful by nature, most himself when he is following game and the growing seasons of plants, peacefully trading with other groups of people and intermarrying.