Toynbee by showing how the separate civilizations of Eurasia interacted from the very beginning of their history, borrowing critical skills from one another, and thus precipitating still further change as adjustment between traditional old and borrowed new knowledge and practice became necessary. McNeill took a broad approach organized around the interactions of peoples across the Earth. Such interactions have become both more numerous and more continual and substantial in recent times. Before about 1500, the network of communication between cultures was that of Eurasia. The term for these areas of interaction differ from one world historian to another and include world-system and ecumene. The importance of these intercultural contacts has begun to be recognized by many scholars. History education United States As early as 1884, the American Historical Association advocated the study of the past on a world scale. T. Walter Wallbank and Alastair M. Taylor co-authored Civilization Past & Present, the first world-history textbook published in the United States (1942). With additional authors, this very successful work went through numerous editions up to the first decade of the twenty-first century. According to the Golden Anniversary edition of 1992, the ongoing objective of Civilization Past & Present "was to present a survey of world cultural history, treating the development and growth of civilization not as a unique European experience but as a global one through which all the great culture systems have interacted to produce the present-day world. It attempted to include all the elements of history – social, economic, political, religious, aesthetic, legal, and technological." Just as World War I strongly encouraged American historians to expand the study of Europe than to courses on Western civilization, World War II enhanced the global perspectives, especially regarding Asia and Africa. Louis Gottschalk, William H. McNeill, and Leften S. Stavrianos became leaders in the integration of world history to the American College curriculum. Gottschalk began work on the UNESCO 'History of Mankind: Cultural and Scientific Development' in 1951. McNeill, influenced by Toynbee, broadened his work on the 20th century to new topics. Since 1982 the World History Association at several regional associations began a program to help history professors broaden their coverage in freshman courses; world history became a popular replacement for courses on Western civilization. Professors Patrick Manning, at the University of Pittsburgh's World History Center; and Ross E. Dunn at San Diego State are leaders in promoting innovative teaching methods.