This overview of the book introduces the Human System as an open, historical, and adaptive system, formed 70,000 years ago by a founding human community as its members created syntactic language. The system grew to the point where it is now in trouble because of excessive growth and painful social inequality. Analysis relies on Darwinian assumptions of evolutionary growth – biological, cultural, and social – as these processes coevolve with each other and with Gaia, a model of the natural world of living things. The discipline of world history is introduced to provide the framework for the narrative and the underlying analysis: world history combines concepts, data, and perspectives from multiple disciplines in natural and social sciences. It gives special attention to behavior of human groups as well as individuals. The chapter concludes by reviewing the book’s argument, presenting two or three historical and analytical hypotheses for each chapter: these hypotheses are to be documented, tested, and debated in the details of each chapter.