BRONZE AGE: Second age of the Three Age System, beginning about 4000– 3000 bc in the Middle East and about 2000–1500 bc in Europe. It followed the Stone Age and preceded the Iron Age and was defined by a shift from stone tools and weapons to the use of bronze. During this time civilization based on agriculture and urban life developed. Trading to obtain tin for making bronze led to the rapid diffusion of ideas and technological improvements. Bronze artifacts were valued highly and became part of many hoards. In the Americas, true bronze was used in northern Argentina before ad 1000 and its use spread to Peru and the Incas. Bronze was never as important in the New World as in the Old. The Bronze Age is often divided into three periods: Early Bronze Age (c. 4000–2000 bc), Middle Bronze Age (c. 2000–1600 bc), and Late Bronze Age (c. 1600–1200 bc) but the chronological limits and the terminology vary from region to region.