The World interweaves two stories‎-of our interactions with nature and with each other‎.‎ The environment‎-centered story is about humans distancing themselves from the rest of nature and searching for a relationship that strikes a balance between constructive and destructive exploitation‎.‎ The culture‎-centered story is of how human cultures have become mutually influential and yet mutually differentiating‎.‎ Both stories have been going on for thousands of years‎.‎ We do not know whether they will end in triumph or disaster‎.‎ There is no prospect of covering all of world history in one book‎.‎ Rather‎,‎ the fabric of this book is woven from selected strands‎.‎ Readers will see these at every turn‎,‎ twisted together into yarn‎,‎ stretched into stories‎.‎ Human‎-focused historical ecology‎-the environmental theme‎-will drive readers back‎,‎ again and again‎,‎ to the same concepts‎:‎ sustenance‎,‎ shelter‎,‎ disease‎,‎ energy‎,‎ technology‎,‎ art‎.‎ ‎(‎The last is a vital category for historians‎,‎ not only because it is part of our interface with the rest of the world‎,‎ but also because it forms a record of how we see reality and of how the way we see it changes‎.‎‎)‎ In the global story of human interactions‎-the cultural theme‎-we return constantly to the ways people make contact with each another‎:‎ migration‎,‎ trade‎,‎ war‎,‎ imperialism‎,‎ pilgrimage‎,‎ gift exchange‎,‎ diplomacy‎,‎ travel‎-and to their social frameworks‎:‎ the economic and political arenas‎,‎ the human groups and groupings‎,‎ the states and civilizations‎,‎ the sexes and generations‎,‎ the classes and clusters of identity‎.‎